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Nonrenewable Energy Sources, Their Impacts, and Energy Conservation Upon completing this chapter, you will be able to:

➤ Identify the energy sources that we use ➤ Describe the nature and origin of coal, natural gas, and crude oil, and evaluate their extraction and use ➤ Assess concerns over the future depletion of global oil supplies ➤ Describe the nature and potential of alternative fossil fuels ➤ Outline and assess environmental, political, social, and economic impacts of fossil fuel use, and explore

potential solutions ➤ Specify strategies for conserving energy and enhancing efficiency ➤ Describe nuclear energy and how we harness it ➤ Assess the benefits and drawbacks of nuclear power, and outline the societal debate over this energy source

The Deepwater Horizon drilling rig on fire, April 2010

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The catastrophe in the Gulf began on April 20, 2010, when a large bubble of natu- ral gas rose through the drill pipe at the Macondo well be- ing drilled by British Petro- leum (BP) a mile underwater. The gas bubble shot past a malfunctioning blowout pre- venter and set off a fiery explosion atop the Deepwater Horizon platform, which sank two days later. The stage had been set by a series of set- backs that put the drilling behind schedule and led BP and its contractors to cut corners while govern- ment regulators looked the other way.

As oil spewed from the seafloor at a rate of 2,000 gallons every minute, response efforts swung into ac- tion. Dozens of ships and boats tried to corral the ris- ing oil at the surface and burn off what they could. Planes and helicopters dumped chemical dispersants from the air. Thousands of people in protective Tyvek suits walked the beaches and spread booms to soak up oil. Teams surveyed marshes for contamination

and captured oiled birds and wildlife to clean and release. The work was hot, dirty, and difficult, and the scale of the job seemed overwhelming.

By the time BP engineers finally got the well sealed 86 days later, roughly 4.9 million barrels (230 million gallons) of crude oil had entered the Gulf, creating the largest ac- cidental oil spill in history. As oil washed ashore, it coated beaches and salt marshes,

killing birds, turtles, crabs, fish, and plants, and spoiling tourism for an entire summer. Thousands of fisher- men were thrown out of work as some of the nation’s most productive fisheries were shut down.

Many Americans who watched news coverage of the spill day after day felt shock and outrage. Indeed, the Gulf oil spill resulted from careless missteps by a corporation and its contractors under weak oversight from the federal government. However, the spill is perhaps best viewed not as a single isolated instance of bad practice or misfortune, but as a by-product of

CE N T R A L C A S E S T U DY

Offshore Drilling and the Deepwater Horizon Blowout

“This oil spill is the worst environmental disaster America has ever faced.” —U.S. President Barack Obama, 2010

“The Deepwater Horizon incident is a direct consequence of our global addiction to oil. . . . If this isn’t a call to green power, I don’t know what is.”

—University of Georgia Researcher Dr. Mandy Joye, 2010

I t began with a spectacular and deadly explosion that killed 11 people far out to sea. It

captivated a horrified nation for three months. And its consequences will stretch on for

years. The collapse of British Petroleum’s Deepwater Horizon drilling rig and the resulting

oil spill from its Macondo well in the Gulf of Mexico polluted water, beaches, and marshes;

shut down fisheries; ruined tourism; and killed countless animals. The oil contaminated over

1,050 km (650 mi) of coastline in Louisiana, Mississippi, Alabama, and Florida (FIGURE 15.1). Ulti-

mately, it raised the question of what costs we are prepared to accept in order to continue

relying on fossil fuel energy.

TEXAS LOUISIANA

MISSISSIPPI

ALABAMA

FLORIDA

Gulf Of Mexico MEXICO

Area of oil spill

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SOURCES OF ENERGY Humanity has devised many ways to harness the renewable and nonrenewable forms of energy available on our planet (TABLE 15.1). We use these energy sources to heat and light our homes; power our machinery; fuel our vehicles; produce plastics, pharmaceuticals, and synthetic fibers; and provide the comforts and conveniences to which we’ve grown accus- tomed in the industrial age.

We use a variety of energy sources Most of Earth’s energy comes from the sun. We can har- ness energy from the sun’s radiation directly by using solar power technologies. Solar radiation also helps drive wind and the water cycle, enabling us to harness wind power and hydroelectric power. And of course, sunlight drives pho- tosynthesis (p. 30) and the growth of plants, from which we take wood and other biomass as a fuel source. Finally, when plants die, some may impart their stored chemical en- ergy to fossil fuels, highly combustible substances formed from the remains of organisms from past geologic ages. The three fossil fuels we use widely today are oil, coal, and natu- ral gas.

Fossil fuels provide most of the energy that our econ- omy buys, sells, and consumes, because their high energy content makes them efficient to ship, store, and burn. We use these fuels for transportation, heating, and cooking, and also to generate electricity, a secondary form of energy that is easier to transfer over long distances and apply to a variety of uses. Global consumption of the three main fossil fuels

Very light oiling

Oil on shoreline

Light oiling

Medium oiling

Heavy oiling

1-10 days

Oil on water surface

10-30 days

More than 30 days

ALABAMA GEORGIA

FLORIDA LOUISIANA

MISSISSIPPI Lake Pontchartrain

Macondo Well (site of Deepwater Horizon blowout)

Tallahassee

TampaNew Orleans

(a) Extent of the oil spill

(b) Workers scrub oil from a Louisiana beach

FIGURE 15.1  Oil from the Macondo well blowout spread over thousands of square miles of the Gulf of Mexico (a) in the spring and summer of 2010. Darker areas indicate more days with signs of oil at the surface. Thousands of volunteers, government officials, and citizens paid by British Petroleum assisted (b) in the vast cleanup effort. Source (a): National Geographic and NOAA.

our society’s insatiable appetite for petroleum, driven largely by our reliance on automobiles. Our thirst for fossil fuels has led the oil industry to drill farther and farther out to sea, in search of larger and more prof- itable untapped deposits. In many cases it has found them, but the farther it moves offshore, the more risks build for major accidents that are hard to control.

Until we reduce our dependence on oil and shift to clean and renewable energy sources, we will suf- fer pollution in the sea and in the air, climate change and health impacts from fossil fuel combustion, and economic uncertainty from reliance on foreign sources of oil. Every once in a while, some drastic event makes these costs painfully apparent. The Deepwater Hori- zon spill was not the first such event, and it will likely not be the last. �

TABLE 15.1 Energy Sources We Use Today Energy source Description Type of energy

Crude oil Fossil fuel extracted from ground (liquid)

Nonrenewable

Natural gas Fossil fuel extracted from ground (gas)

Nonrenewable

Coal Fossil fuel extracted from ground (solid)

Nonrenewable

Nuclear energy Energy from atomic nuclei of uranium

Nonrenewable

Biomass energy Energy stored in plant matter from photosynthesis

Renewable

Hydropower Energy from running water

Renewable

Solar energy Energy from sunlight directly

Renewable

Wind energy Energy from wind Renewable

Geothermal energy

Earth’s internal heat rising from core

Renewable

Tidal and wave energy

Energy from tidal forces and ocean waves

Renewable

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Higher EROI ratios mean that we receive more energy from each unit of energy that we invest. Fossil fuels are widely used because their EROI ratios have historically been high. How- ever, EROI ratios can change over time. Those for U.S. oil and natural gas have declined from over 100:1 in the 1940s to about 5:1 today. This means that we used to be able to gain 100 units of energy for every unit of energy expended, but now we can gain only five. The EROI ratios for oil and gas declined because we extracted the easiest deposits first and now must work harder and harder to extract the remaining amounts.

Energy and its consumption are unevenly distributed Most energy sources are localized and unevenly distributed over Earth’s surface. This is true of oil, coal, and natural gas, and as a result, some regions have substantial reserves of fos- sil fuels whereas others have very few. Nearly two-thirds of the world’s proven reserves of crude oil lie in the Middle East. The Middle East is also rich in natural gas, but Russia holds more natural gas than any other country. Russia is also rich in coal, as is China, but the United States possesses the most coal of any nation (TABLE 15.2).

has risen steadily for years and is now at its highest level ever (FIGURE 15.2).

Energy sources such as sunlight, geothermal energy, and tidal energy are considered perpetually renewable because they are readily replenished, and so we can keep using them without depleting them (pp. 2–3). In contrast, energy sources such as oil, coal, and natural gas are considered nonrenew- able. These nonrenewable fuels result from ongoing natural processes, but it takes so long for fossil fuels to form that, once depleted, they cannot be replaced within any time span useful to our civilization. It takes a thousand years for the biosphere to generate the amount of organic matter that must be buried to produce a single day’s worth of fossil fuels for our society. At our current rate of consumption, we will use up Earth’s ac- cessible store of fossil fuels in just decades to centuries.

Nuclear power as currently harnessed through the fission of uranium (p. 346) is nonrenewable to the extent that ura- nium ore is in limited supply. However, we can also reprocess some uranium and reuse it.

It takes energy to make energy We do not simply get energy for free. To harness, extract, process, and deliver the energy we use, we need to invest sub- stantial inputs of energy. For instance, drilling for oil offshore in the Gulf of Mexico requires the construction of immense drilling platforms (the Deepwater Horizon cost $560 million) and extensive infrastructure to extract and transport oil— all requiring the use of huge amounts of energy. Thus, when evaluating how much energy a source gives us, it is important to subtract costs in energy invested from benefits in energy received. Net energy expresses the difference between en- ergy returned and energy invested:

Net energy = Energy returned – Energy invested

When assessing energy sources, it is useful to use a ratio often denoted as EROI, which stands for energy returned on investment. EROI ratios are calculated as follows:

EROI = Energy returned / Energy invested

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0 1950 1960 1970 1980

Year

1990

Oil

Coal

Natural gas

2000 2010

FIGURE 15.2  Global consumption of fossil fuels has risen greatly over the past half century. Oil use rose steeply during the 1960s to overtake coal, and today it remains our leading energy source. Data from U.S. Energy Information Administration, International Energy Agency, and BP plc. 2011. Statistical review of world energy 2011.

TABLE 15.2 Nations with the Largest Proven Reserves of Fossil Fuels Oil (% world reserves)

Natural gas (% world reserves)

Coal (% world reserves)

Saudi Arabia, 17.3 Russia, 23.9 United States, 27.6

Venezuela, 13.8* Iran, 15.8 Russia, 18.2

Canada, 11.5* Qatar, 13.5 China, 13.3

Iran, 9.0 Turkmenistan, 4.3 Australia, 8.9

Iraq, 7.5 Saudi Arabia, 4.3 India, 7.0

*Most of Canada’s and Venezuela’s oil reserves occur as oil sands (p. 335), which are included in these figures. Data are for 2010, from BP plc. 2011. Statistical review of world energy 2011.

Consumption rates across the world are also uneven. Citizens of developed regions generally consume far more energy than do those of developing regions. The United States has only 4.5% of the world’s population, but it consumes over 20% of the world’s energy. Nations also differ in how they use energy. Developing nations devote a greater proportion of en- ergy to subsistence activities, such as growing and preparing food and heating homes, whereas industrialized countries use a greater proportion for transportation and industry. Because industrialized nations rely more on mechanized equipment and technology, they use more fossil fuels. In the United States, fossil fuels supply 83% of energy needs.

COAL, NATURAL GAS, AND OIL The three major fossil fuels on which we rely today are coal, natural gas, and oil. We will first consider how these fossil fu- els are formed, how we locate deposits, how we extract these resources, and how our society puts them to use. We will then examine some environmental and social impacts of their use.

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Coal is a hard blackish substance formed from organic matter (generally woody plant material) that was compressed under very high pressure, creating dense, solid carbon struc- tures. Coal typically results when water is squeezed out of the material as pressure and heat increase and time passes, and when little decomposition takes place because the ma- terial cannot be digested or appropriate decomposers are not present. The proliferation 300–400 million years ago of swampy environments where organic material was buried has created coal deposits throughout the world.

Natural gas is a gas consisting primarily of methane (CH4) and including varying amounts of other volatile hydro- carbons. Oil, or crude oil, is a sludge-like liquid containing a mix of various hydrocarbon molecules. Oil is also known as petroleum, although this term is commonly used to refer to oil and natural gas collectively. Both natural gas and oil have formed from organic material (especially dead plankton) that drifted down through coastal marine waters millions of years ago and was buried in sediments on the ocean floor. This or- ganic material was transformed by time, heat, and pressure into today’s natural gas and crude oil.

Two processes give rise to natural gas. Biogenic gas is created at shallow depths by the anaerobic decomposition of organic matter by bacteria. An example is the “swamp gas” you may smell when stepping into the muck of a swamp. One source of biogenic natural gas is the decay process in landfills, and many landfill operators are now capturing this gas to sell as fuel (p. 385). Thermogenic gas results from compression and heat deep underground. Thermogenic gas may form directly, along with coal or crude oil, or from coal or oil that is altered by heating. Most gas that we extract commercially is thermogenic and is found above deposits of crude oil or seams of coal, so it is often extracted along with those fossil fuels. Indeed, the Deepwater Horizon blowout occurred because natural gas ac- companying the oil deposit shot up the well shaft once drilling relieved the pressure, and ignited atop the platform.

Because fossil fuels form only under certain conditions, they occur in isolated deposits. For instance, oil and natural gas tend to rise upward through cracks and fissures in porous rock until meeting a dense impermeable rock layer that traps them. Geologists searching for fossil fuels drill cores and conduct ground, air, and seismic surveys to map underground rock formations and predict where fossil fuel deposits might lie.

We mine coal and use it to generate electricity Coal is the world’s most abundant fossil fuel, and it provides 27% of our global primary energy consumption. Once a coal seam is located, we extract coal from the ground using sev- eral methods. For deposits near the surface, we use strip min- ing, whereas for deposits deep underground, we use subsur- face mining (see Figure 11.14, p. 238). Recently, we have begun mining coal on immense scales in the Appalachian Moun- tains, essentially scraping off entire mountaintops in a proc- ess called mountaintop removal mining (p. 240). (We explored mining practices and their impacts more fully in Chapter 11.)

People have burned coal to cook food, heat homes, and fire pottery for thousands of years. Coal-fired steam engines helped drive the industrial revolution, powering factories,

Fossil fuels are indeed fuels created from “fossils” Fossil fuels form only after organic material is broken down over millions of years in an anaerobic environment, one with little or no oxygen. Such environments include the bottoms of lakes, swamps, and shallow seas. The fossil fuels we burn today in our vehicles, homes, industries, and power plants were formed from the tissues of organisms that lived 100–500 million years ago. When organisms were buried quickly in anaerobic sediments after death, chemical energy in their tissues became concentrated as the tissues decomposed and their hydrocarbon compounds (p. 28) were chemically al- tered amid heat and compression (FIGURE 15.3).

Woody terrestrial vegetation dies and falls into swamp

Organic matter from woody land plants partly decomposed by microbes under accumulating sediments; kerogen forms

Coal formed from kerogen

Phytoplankton, zooplankton, and other marine organisms die and sink to sea floor

Organic matter from soft-bodied sea life partly decomposed by microbes under accumulating sediments; some carbon bonds broken; kerogen forms

Thermogenic natural gas formed from kerogen

Crude oil formed from kerogen

Ancient swamp

Anaerobic conditions

Present day

Heat and pressure deep underground

alter kerogen

Ancient ocean

FIGURE 15.3  Fossil fuels begin to form when organisms die and end up in oxygen-poor conditions, such as when trees fall into lakes and are buried by sediment, or when phytoplankton and zooplankton drift to the seafloor and are buried (top diagram). Or- ganic matter that undergoes slow anaerobic decomposition deep under sediments forms kerogen (middle diagram). Geothermal heating then acts on kerogen to create crude oil and natural gas (bottom diagram). Oil and gas come to reside in porous rock lay- ers beneath dense, impervious layers. Coal is formed when plant matter is compacted so tightly that there is little decomposition.

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coal combustion, along with solutions to these problems, later in this chapter (pp. 336, 341). Reducing pollution from coal is important because society’s demand for this abundant fossil fuel may rise once supplies of oil and natural gas begin to decline. Scientists estimate that Earth holds enough coal to supply our society for perhaps a few hundred years more— far longer than oil or natural gas will remain available.

Natural gas burns cleaner than coal Natural gas today provides over one-fifth of global primary energy consumption. Versatile and clean-burning, natural gas emits just half as much carbon dioxide per unit of energy pro- duced as coal and two-thirds as much as oil. We use natural gas to generate electricity in power plants, to heat and cook in our homes, and for much else. Converted to a liquid at low temperatures (liquefied natural gas, or LNG), it can be shipped long distances in refrigerated tankers. Russia and the United States lead the world in gas production and gas consumption, respectively (TABLE 15.4). World supplies of natural gas are projected to last perhaps 60 more years.

Oil is the world’s most-used fuel Oil today accounts for one-third of the world’s primary ener- gy consumption. Global oil consumption has risen 15% in the past decade, and today our society produces and consumes over 750 L (200 gal) of oil annually for every man, woman, and child. TABLE 15.5 shows the top oil-producing and oil- consuming nations.

agriculture, trains, and ships. Today we burn coal largely to generate electricity. In coal-fired power plants, coal combus- tion converts water to steam, which turns a turbine to create electricity (FIGURE 15.4). Coal provides half the electrical gen- erating capacity of the United States, and it powers China’s surging economy. China and the United States are the prima- ry producers and consumers of coal (TABLE 15.3).

Coal varies from deposit to deposit in its water content, carbon content, and potential energy. Coal deposits also vary in the amount of impurities they contain, including sulfur, mercury, arsenic, and other trace metals. Coal from the east- ern United States tends to be high in sulfur because it was formed in marine sediments, where sulfur from seawater was present. The impurities in coal are emitted during its combus- tion unless pollution control measures are in place. We will examine the many health and environmental impacts from

Boiler

Turbine

Cooling loop

Filter

Furnace

Pulverizing mill

Coal bunker

Stack

Ash disposal

Condenser

Generator

Cooling tower

FIGURE 15.4  At a coal-fired power plant, coal is pulverized and blown into a high-temperature furnace. Heat from the combustion boils water, and the resulting steam turns a turbine, generating electricity by passing mag- nets past copper coils. The steam is then cooled and condensed in a cooling loop and returned to the furnace. “Clean coal” technologies (pp. 336–337) help filter out pollutants from the combustion process, and toxic ash residue is taken to hazardous waste disposal sites.

TABLE 15.3 Top Producers and Consumers of Coal Production (% world production)

Consumption (% world consumption)

China, 43.8 China, 45.9

United States, 14.0 United States, 13.2

India, 8.0 India, 9.0

Australia, 5.7 Germany, 3.3

Indonesia, 4.3 Russia, 2.9 Data are for 2009, from U.S. Energy Information Administration, 2011.

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In the United States, many oil fields did not undergo sec- ondary extraction because the price of oil was too low to make it economical. Once oil prices rose in the 1970s, companies reopened those drilling sites for secondary extraction. More are being reopened today. The amount of a fossil fuel that is technologically and economically feasible to remove under current conditions is termed its proven recoverable reserve.

Some drilling occurs offshore We drill for oil and natural gas not only on land but also be- low the seaf loor on the continental shelves (FIGURE 15.6). Offshore drilling has required us to develop technology that can withstand wind, waves, and ocean currents. Some drill- ing rigs are fixed, standing platforms built with unusual strength. Others are resilient f loating platforms anchored in

We drill to extract oil and gas Once geologists have identified a promising location for an oil or natural gas deposit, a company will typically conduct explor- atory drilling, drilling small holes that descend to great depths. If enough oil or gas is encountered, extraction begins. Because oil and gas are generally under pressure while in the ground, they will rise to the surface of their own accord when a deposit is tapped. Once pressure is relieved and some oil or gas has risen to the surface, however, the remainder becomes more difficult to extract and may need to be pumped out. As much as two-thirds of a deposit may remain in the ground following primary ex- traction, the initial extraction of available oil or gas. Companies may then begin secondary extraction. In secondary extraction for oil, solvents are used or underground rocks are flushed with water or steam (FIGURE 15.5). For gas, we use “fracturing tech- niques” to break into rock formations and pump gas upward. One such technique is to pump salt water under high pressure into rocks to crack them. Sand or small glass beads are injected to hold the cracks open once the water is withdrawn. Even after secondary extraction, quite a bit of oil or gas can remain; we lack technology to remove the entire amounts.

While technology sets a limit on how much can be ex- tracted, economics determines how much will be extracted. This is because extraction becomes increasingly difficult and costly as oil or gas is removed, so companies will not find it profitable to extract the entire amount. Instead, a company will consider the costs of extraction (and other expenses), and balance them against the current price of the fuel on the world market. Because fuel prices fluctuate, the portion of oil or gas from a given deposit that is “economically recoverable” fluctuates as well. At higher prices, economically recoverable amounts approach technically recoverable amounts.

TABLE 15.4 Top Producers and Consumers of Natural Gas Production (% world production)

Consumption (% world consumption)

United States, 19.7 United States, 21.4

Russia, 19.4 Russia, 14.5

Canada, 5.3 Iran, 4.4

Iran, 4.4 Japan, 3.3

Norway, 3.4 Germany, 3.1 Data are for 2009, from U.S. Energy Information Administration, 2011.

TABLE 15.5 Top Producers and Consumers of Oil Production (% world production)

Consumption (% world consumption)

Russia, 11.8 United States, 22.3

Saudi Arabia, 11.6 China, 9.9

United States, 10.8 Japan, 5.3

Iran, 4.9 India, 3.7

China, 4.7 Russia, 3.2 Data are for 2009, from U.S. Energy Information Administration, 2011.

Ocean �oor

Impermeable rock

Oil in pores of rocks

Oil rig

Gas cap

Gas injection

Seawater injection

PressurePressure

Oil well

FIGURE 15.5  Once pressure on an oil deposit drops, material must be injected to increase the pressure. Secondary extraction involves injecting seawater beneath the oil and/or injecting gases just above the oil to force more oil up and out of the deposit.

FIGURE 15.6  Offshore drilling platforms allow the oil industry to drill for petroleum in the seafloor on the continental shelves.

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place above the drilling site. Roughly 35% of the oil and 10% of the natural gas extracted in the United States today comes from offshore sites, primarily in the Gulf of Mexico and sec- ondarily off southern California. The Gulf today is home to 90 drilling rigs and 3,500 production platforms.

Geologists estimate that most U.S. oil and gas remaining to be extracted occurs offshore, and that deepwater sites in the Gulf of Mexico alone may hold 59 billion barrels of oil. We have been drilling in shallow water for several decades, but as oil and gas are depleted at shallow-water sites and as drilling technology improves, the industry is moving into deeper and deeper water. BP’s Macondo well lay beneath 1,500 m (5,000 ft) of water, but the deepest wells in the Gulf of Mexico are now twice that depth. Globally, recent discoveries off the coasts of Brazil, Angola, Nigeria, and other nations suggest that a great deal of oil and gas could lie well offshore, and companies are racing one another to get there. Unfortunately, our ability to drill in deep water has outpaced our capacity to deal with acci- dents there. The fact that it took 86 days for BP to plug the leak in its Macondo well demonstrates the challenge of addressing

(b) Distillation process

(a) Distillation columns

Boiling temp.

Distillation column

Product

Less than 5ºC Butane

20-180ºC Naphtha

20-200ºC Gasoline

180-260ºC Kerosene

Crude oil

Boiler Residue

260-340ºC Diesel

300-370ºC Lubricating oil

370-600ºC Fuel oil

Gasoline (48.1%)

Diesel fuel and heating oil (19.4%)

Heavy fuel oil (2.8%) Jet fuel (7.5%)

Lique�ed petroleum gases (10.8%)

Other (11.4%)

FIGURE 15.7  At oil refineries (a), crude oil is boiled, causing its many hydrocarbon constituents to volatilize and proceed upward through a distillation column (b). Constituents that boil at the hottest temperatures and condense readily once the temperature cools will condense at low levels in the column. Constituents that volatilize at cooler temperatures will continue rising through the column and condense at higher levels, where temperatures are cooler. In this way, heavy oils (generally those with hydrocarbon molecules with long carbon chains) are separated from lighter oils (generally those with short-chain hydrocarbon molecules). The refining process produces a range of petroleum products. Shown in (c) are percentages of each major category of product typically generated from a barrel of crude oil. Data for (c) from U.S. Energy Information Administration.

an emergency situation a mile or more beneath the surface of the sea.

In 2008 the U.S. Congress lifted a long-standing morato- rium on offshore drilling along much of the nation’s coastline. The administration of President Barack Obama in 2010 then designated vast areas open for drilling. These included most waters along the Atlantic coast from Delaware south to cen- tral Florida, a region of the eastern Gulf of Mexico, and most waters off Alaska’s North Slope. However, just weeks after this announcement, the Deepwater Horizon spill occurred. Public reaction forced the Obama administration to backtrack, can- celing offshore drilling projects it had approved and putting a hold on further approvals until new safety measures could be devised.

Petroleum products have many uses Once we extract crude oil, we refine it (FIGURE 15.7). Crude oil is a mixture of hundreds of types of hydrocarbon molecules characterized by carbon chains of different lengths (p. 28). A

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levels of production (30 billion barrels globally per year), 1.2 trillion barrels would last about 40 more years.

Unfortunately, this does not mean that we have 40 years to figure out what to do once the oil runs out. A growing number of scientists and analysts insist that we will face a cri- sis as soon as the rate of production comes to a peak and then begins to decline—a point in time nicknamed peak oil. They point out that if demand continues to increase (because of rising global population and consumption) while production declines, an oil shortage will result. Because production tends to decline once reserves are depleted halfway, many of these experts calculate that a peak oil crisis will likely begin in the very near future.

To understand the basis of these concerns, we must turn back the clock to 1956. In that year, Shell Oil geologist M. King Hubbert calculated that U.S. oil production would peak around 1970. His prediction was ridiculed at the time, but it proved to be accurate; U.S. production peaked in that very year and has continued to fall since then (FIGURE 15.9A). The peak in production came to be known as Hubbert’s peak.

In 1974, Hubbert analyzed data on technology, eco- nomics, and geology, predicting that global oil production would peak in 1995. It grew past 1995, but many scientists using newer, better data today predict that at some point in the coming decade, production will begin to decline (FIGURE 15.9B). Discoveries of new oil fields peaked 30 years ago, and since then we have been extracting and consuming more oil than we have been discovering.

chain’s length affects its chemical properties, and these have consequences for human use, such as whether a given fuel burns cleanly in a car engine. Oil refineries sort the various hydrocarbons of crude oil, separating those intended for use in gasoline engines from those, such as tar and asphalt, used for other purposes.

Since the 1920s, refining techniques and chemical man- ufacturing have greatly expanded our uses of petroleum to include a wide array of products and applications, from lubricants to plastics to fabrics to pharmaceuticals. Today, petroleum-based products are all around us in our every- day lives (FIGURE 15.8). Because petroleum products have become so central to our lifestyles, many fossil fuel experts today are voicing concern that oil production may soon de- cline as we continue to deplete the world’s recoverable oil reserves.

We may already have depleted half our oil reserves Some scientists and oil industry analysts calculate that we have already extracted half the world’s oil reserves. So far we have used up about 1.1 trillion barrels of oil, and most esti- mates hold that somewhat more than 1 trillion barrels remain. To estimate how long this remaining oil will last, analysts cal- culate the reserves-to-production ratio, or R/P ratio, by di- viding the amount of total remaining reserves by the annual rate of production (i.e., extraction and processing). At current

Cosmetics, medicines, lotions, and soap

Plastic wastebasket

Detergents, cleaning supplies

Nylon and polyester clothing

Light switch Pesticides and fertilizers

Asphalt

Toilet seat

Shoes with synthetic soles

Plastic storage box

Vinyl and plastic laminate furniture

Polypropylene coat

CDs and DVDs Linoleum flooring

Components in TV and stereo

Home heating oil to heat house

Blender and other small appliances

Components of stove and other large appliances

Toothbrush

Shower curtain

Plastic lampshade

ContainersTires, upholstery, and automobile components

Shower head

Plastic picture frame

Bicycle components Gasoline

Paraffin waxes on fruit, candy, and other food

Plastic cups and dishware

Nonstick coating on cookware

FIGURE 15.8  Petroleum products are everywhere in our daily lives. Besides the fuels we use for transportation and heating, petroleum products include many of the fabrics we wear and the plastics in countless items we use every day.

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without petroleum-based fertilizers and pesticides we could feed only a fraction of the world’s 7 billion people, even if we expand agricultural land. The American suburbs would be hit particularly hard because of their utter dependence on the au- tomobile. Kunstler argues that the suburbs will become the slums of the future, a bleak and crime-ridden landscape lit- tered with the hulls of rusted-out SUVs.

More optimistic observers argue that as oil supplies dwindle, rising prices will create powerful incentives for busi- nesses, governments, and individuals to conserve energy, use the more expensive types of fossil fuels like those described on the next page, and develop alternative energy sources (Chap- ter 16)—and that these developments will save us from major disruptions caused by the coming oil peak.

Indeed, to achieve a sustainable society, we will need to switch to renewable energy sources. Investments in energy ef- ficiency and conservation (pp. 343–345) can extend the time we have to make this transition. However, the research and development needed to construct the infrastructure for a new energy economy depend on having cheap oil, and the time we will have to make this enormous transition will be quite limited.

Predicting an exact date for peak oil is difficult. Because of year-to-year variability in production, we will not be able to recognize that we have passed the peak until several years af- ter the fact. Many companies and governments do not reveal their true data on oil reserves, and estimates differ as to how much oil we can extract secondarily from existing deposits. Indeed, a recent U.S. Geological Survey report estimated 2 tril- lion barrels remaining in the world, rather than 1 trillion, and some estimates predict still greater amounts. A 2007 report by the U.S. General Accounting Office reviewed 21 studies and found that most estimates for the timing of the oil production peak ranged from now through 2040.

Whenever it occurs, the coming divergence of demand and supply will likely have momentous economic, social, and political consequences that will profoundly affect the lives of each and every one of us. One prophet of peak oil, writer James Howard Kunstler, has sketched a frightening scenario of our post-peak world during what he calls “the long emer- gency”: Lacking cheap oil with which to transport goods long distances, today’s globalized economy would collapse, and our economies would become intensely localized. Large cities could no longer be supported without urban agriculture, and

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Hubbert’s prediction assuming a total of 200 billion barrels of discoverable oil (total area under curve)

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(a) Hubbert’s prediction of peak in U.S. oil production, with actual data

(b) Modern prediction of peak in global oil production

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FIGURE 15.9  Because fossil fuels are nonrenewable resources, supplies at some point pass the midway point of their depletion, and annual production begins to decline. U.S. oil production peaked in 1970 (a), just as geologist M. King Hubbert had predicted. Success in Alaska, the Gulf of Mexico, and with sec- ondary extraction increased production above his prediction during the decline. Today many analysts believe global oil production is about to peak. Shown (b) is a recent projection, from a 2009 analysis by scientists at the Association for the Study of Peak Oil. Data for (a) from Hubbert, M.K., 1956. Nuclear energy and the

fossil fuels. Shell Development Co. Publ. No.

95, Houston, TX; and U.S. Energy Information

Administration; and for (b) from Campbell,

C.J., and Association for the Study of Peak Oil.

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Three-quarters of the world’s oil sands occur in Venezue- la and in Alberta, Canada. In Alberta, strip mining began in 1967. Rising crude oil prices have made oil sands more profit- able, and dozens of companies are now angling to begin min- ing projects in the region. Canadian oil sands are now produc- ing well over 1 million barrels of oil per day, contributing half of Canada’s petroleum production.

Oil shale Oil shale is sedimentary rock filled with kerogen (organic matter) and can be processed to produce liquid pe- troleum. Oil shale is formed by the same processes that form crude oil but results when kerogen was not buried deeply enough or subjected to enough heat and pressure to form oil.

We mine oil shale using strip mines or subsurface mines. Once mined, oil shale can be burned directly like coal, or can be baked in the presence of hydrogen and in the absence of air to extract liquid petroleum. The world’s known deposits of oil shale may be able to produce over 600 billion barrels of oil (roughly half as much as the conventional crude oil remaining in the world). About 40% of global oil shale reserves are in the United States, mostly on federally owned land in Colorado, Wyoming, and Utah.

Methane hydrate Another novel potential source of fos- sil fuel energy occurs in sediments on the ocean f loor. Meth- ane hydrate (also called methane clathrate or methane ice ) is an ice-like solid consisting of molecules of methane (CH 4 , the main component of natural gas) embedded in a crystal lattice of water molecules. Methane hydrate is stable at tem- perature and pressure conditions found in many sediments on the Arctic seaf loor and the continental shelves.

Scientists believe there to be immense amounts of meth- ane hydrate on Earth, holding perhaps twice as much carbon as all known deposits of oil, coal, and natural gas combined. However, we do not yet know how to extract these energy sources safely. Destabilizing a methane hydrate deposit dur- ing extraction could lead to a catastrophic release of gas. This could cause a massive landslide and tsunami and would also release huge amounts of methane, a potent greenhouse gas, into the atmosphere, worsening global climate change.

Other fossil fuels exist As oil production declines, we will rely more on natural gas and coal—yet these in turn will also eventually peak and de- cline. At least three further types of fossil fuels exist in large amounts: oil sands, oil shale, and methane hydrate.

Oil sands Oil sands (also called tar sands ) are deposits of moist sand and clay containing 1–20% bitumen , a thick and heavy form of petroleum that is rich in carbon and poor in hydrogen. Oil sands represent crude oil deposits that have been degraded and chemically altered by water erosion and bacterial decomposition. Bitumen is too thick to extract by conventional oil drilling, so oil sands are generally removed by strip mining ( FIGURE 15.10 ). After extraction, bitumen may be sent to specialized refineries, where chemical reac- tions that add hydrogen or remove carbon can upgrade it into more valuable synthetic crude oil.

FAQ

Q: Why should I worry about “peak oil” if there are still years of oil left in the ground? A: The first thing to bear in mind is that the term “peak oil” doesn’t refer to running out of oil. It refers to

the point at which our production of oil comes to a peak. Once we pass this peak and production begins to decline, the economics of supply and demand take over. Supply will fall, with some estimates putting the decline at 5% per year. Demand, meanwhile, is forecast to continue rising, especially as nations like China and India put millions of new vehicles on the road. The divergence of demand and supply will drive up oil prices, causing substantial economic ripple effects. Although high oil prices will provide financial incentive to develop alternative energy sources, we may be challenged in a depressed economy to find adequate time and resources to develop new renewable sources.

FIGURE 15.10  In Alberta, com- panies strip-mine oil sands with the world’s largest dump trucks and power shovels. On average, 2 met- ric tons of oil sands are required to produce 1 barrel of synthetic crude oil.

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coal in our power plants releases sulfur dioxide and nitrogen oxides, which contribute to smog (pp. 287–289) and acid dep- osition (pp. 291–294). Combustion of coal may emit mercury that can bioaccumulate in organisms’ tissues, poisoning ani- mals as it moves up food chains (pp. 216–217) and presenting health risks to people.

Air pollution from fossil fuel combustion is increasing in developing nations that are industrializing rapidly, but it has been reduced in developed nations as a result of laws such as the U.S. Clean Air Act and government regulations to pro- tect public health (Chapter 13). Technologies such as catalytic converters that cut down on vehicle exhaust pollution have helped a great deal, and their wider adoption in the develop- ing world would reduce pollution further. Regarding pollu- tion from coal-fired power plants, scientists and engineers are seeking ways to cleanse coal of its impurities so that it can continue to be used as an energy source while minimizing im- pacts on health and the environment.

Clean coal technologies aim to reduce pollution from coal Clean coal technologies refer to a wide array of techniques, equipment, and approaches that aim to remove chemical con- taminants during the process of generating electricity from coal. Among these technologies are various types of scrubbers (pp. 285–286), devices that chemically convert or physically remove pollutants. Another approach is to dry coal that has high water content, making it cleaner-burning. We can also gain more power from coal with less pollution through a proc- ess called gasification, in which coal is converted into a cleaner synthesis gas, or syngas, by reacting it with oxygen and steam at a high temperature. Syngas from coal can be used to turn a gas turbine or to heat water to turn a steam turbine.

Alternative fossil fuels have drawbacks Oil sands, oil shale, and methane hydrate are abundant, but they are no panacea for our energy challenges. For one thing, their net energy values are low, because they are expensive to extract and process. Thus the ratio of energy returned on energy invested (EROI) is low. For instance, much of the en- ergy content of oil shale is consumed in its production, and oil shale’s EROI is only about 2:1 or 3:1, compared to a 5:1 or greater ratio for conventional crude oil.

Second, these fuels exert severe environmental impacts. Oil sands and oil shale require extensive strip mining, which devastates landscapes and pollutes waterways. Mining these resources also requires an immense amount of water (which is often scarce in mining regions). At Alberta’s oil sands mines, polluted wastewater is left to sit in gigantic reservoirs where waterfowl can die once they land. Besides impacts from their extraction, our combustion of alternative fossil fuels would emit at least as much carbon dioxide, methane, and other air pollutants as our use of coal, oil, and gas. This would worsen the impacts that fossil fuels are already caus- ing, including air pollution and global climate change.

ADDRESSING IMPACTS OF FOSSIL FUEL USE Our society’s love affair with fossil fuels and the many pet- rochemical products we develop from them has eased con- straints on travel, helped lengthen our life spans, and boosted our material standard of living beyond what our ancestors could have dreamed. However, it also causes harm to the en- vironment and human health, and it can lead to political and economic instability.

Fossil fuel emissions pollute air and drive climate change When we burn fossil fuels, we alter fluxes in Earth’s carbon cycle (pp. 38–39). We essentially take carbon that had been retired into a long-term reservoir underground and release it into the air. This occurs as carbon from the hydrocarbon mol- ecules of fossil fuels unites with oxygen from the atmosphere during combustion, producing carbon dioxide (CO2). Carbon dioxide is a greenhouse gas (p. 300), and CO2 released from fossil fuel combustion warms our planet and drives changes in global climate (Chapter 14). Because climate change may have diverse, severe, and widespread ecological and socioeconomic impacts, carbon dioxide pollution (FIGURE 15.11) is becoming recognized as the greatest environmental impact of fossil fuel use. Moreover, methane is a potent greenhouse gas that drives climate warming. Across the world today, many avenues are being considered to address climate change (pp. 316–323).

Besides modifying our climate, fossil fuel emissions affect human health. Gasoline combustion in automobiles releases pollutants that irritate the nose, throat, and lungs, as well as hydrocarbons (such as benzene and toluene) and impurities (such as lead and arsenic) known to cause cancer or other se- rious health risks. The combustion of oil in our vehicles and

Total

Coal Oil

Natural gas

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FIGURE 15.11  Emissions from fossil fuel combustion have risen dramatically as industrialization has proceeded and as population and consumption have grown. Here, global emissions of carbon from carbon dioxide are subdivided by their source (oil, coal, or natural gas). Other minor sources (such as cement production) are also included in the graphed total. Data from Carbon Dioxide Informa- tion Analysis Center, Oak Ridge National Laboratory, U.S. Department of

Energy, Oak Ridge, TN.

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where a Canadian oil company buys it to inject into an oilfield to help it pump out oil.

Currently the U.S. Department of Energy is teaming up with nine energy companies to build a prototype of a near-zero- emissions coal-fired power plant. The $1.5 billion FutureGen project, located in Mattoon, Illinois, aims to design, construct, and operate a power plant that burns coal using gasification and combined cycle generation, produces electricity and hydrogen, then captures its carbon dioxide emissions and sequesters the CO2 underground. If this showcase project succeeds, it could be a model for a new generation of power plants.

Energy experts are not ready to rely on the unproven tech- nology of carbon capture and storage quite yet, however. We do not know how to ensure that CO2 will stay underground once injected there, and we do not know whether these at- tempts might trigger earthquakes. Injection could in some cases contaminate groundwater supplies, and injecting carbon dioxide into the ocean would acidify its waters (pp. 259, 311). Moreover, CCS is energy-intensive and decreases the EROI of coal, adding to its cost and the amount we need to use. Finally, many renewable energy advocates fear the CCS approach takes the burden off emitters and prolongs our dependence on fossil fuels rather than facilitating a shift to renewables.

Clean Coal and Carbon Capture Do you think we should be spending billions of dollars to try to find ways to burn coal cleanly and to sequester carbon emissions from fossil fuels?

Or is our money better spent on developing new clean and renewable energy sources, even though they do not yet have enough infrastructure to produce power at the scale that coal can? What pros and cons do you see in each approach?

The U.S. government and the coal industry have each in- vested billions of dollars in clean coal technologies, and these have helped to reduce air pollution from sulfates, nitrogen oxides, mercury, and particulate matter (p. 285). At the same time, the coal industry spends a great deal of money fighting regulations and mandates on its practices. As a result, many power plants are built with little in the way of clean coal tech- nologies, and these plants will continue polluting our air for decades. Moreover, many energy analysts and environmental advocates emphasize that these technologies will never result in energy production that is completely clean. They argue that coal is an inherently dirty way of generating power and that it should be replaced outright with cleaner energy sources.

Can we capture and store carbon? Even if our clean coal technologies were able to remove every last chemical contaminant from power plant emissions, coal combustion would still pump huge amounts of carbon diox- ide into the air, intensifying the greenhouse effect and wors- ening global climate change. This is why many current efforts focus on carbon capture and carbon storage or sequestra- tion (p. 317). This approach consists of capturing carbon di- oxide emissions, converting the gas to a liquid form, and then sequestering (storing) it in the ocean or underground in a geologically stable rock formation (FIGURE 15.12).

Carbon capture and storage (abbreviated as CCS) is be- ing attempted at a variety of new and retrofitted facilities. The world’s first coal-fired power plant to approach zero emis- sions opened in 2008 in Germany. This plant captures its sulfates and carbon dioxide, compresses the CO2 into liquid form, trucks it 160 km (100 mi) away, and injects it 900 m (3,000 ft) underground into a depleted natural gas field. In North Dakota, the Great Plains Synfuels Plant gasifies its coal and then sends half the CO2 through a pipeline into Canada,

CO2

Deep saline aquifer

Coal-fired power plant (emitting CO2)

Oil refinery

Oil or gas reservoir

Abandoned coal seam

FIGURE 15.12  Carbon capture and storage schemes propose to inject liquefied carbon dioxide emissions underground into depleted fossil fuel deposits, deep saline aquifers, or oil or gas deposits undergoing second- ary extraction.

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An EPA scientist takes samples to as- sess impacts of oil on beaches.

when and where oil might reach shore, thereby helping to direct prevention and cleanup efforts.

Tracking movement of the oil underwater was trickier than monitoring its spread on the surface. University of Georgia biochemist Mandy Joye, who had studied natural seeps in the Gulf for years, documented that the leaking wellhead was creating a plume of oil the size of Manhattan. She also found evi- dence of low oxygen concentrations, or hypoxia (pp. 22, 25, 267), resulting from the fact that some bacteria consume oil and gas, depleting the water of oxygen as they proliferate. Hypoxia can make underwater regions uninhabitable for fish and other creatures.

Joye and others worried about im- pacts on marine life in the open ocean and deep beneath the surface. Some researchers feared that the thinly dis- persed oil could prove devastating to plankton (the base of the marine food chain) and to the tiny larvae of shrimp,

fish, and oysters (the pillars of the fish- ing industry). Scientists taking water samples documented sharp drops in plankton during the spill, but it will take a few years to learn whether so many larvae were lost as to diminish popula- tions of adult fish and shellfish.

Other questions revolve around impacts of the chemical dispersant that BP used to break up the oil, a com- pound called Corexit 9500. Work by biologist Philippe Bodin following the Amoco Cadiz oil spill in France in 1978 had found that Corexit 9500 appeared more toxic to marine life than the oil itself. BP applied an unprecedented amount of the chemical to the Deep- water Horizon spill, injecting a great deal directly into the path of the oil at the wellhead. This caused the oil to dis- sociate into trillions of tiny droplets that dispersed across large regions. Many scientists worried that this expanded the oil’s reach, affecting more plank- ton, larvae, and fish.

Impacts of the oil on birds, sea turtles, and marine mammals were somewhat easier to assess. Officially confirmed deaths numbered 6,104 birds, 605 turtles, and 97 mammals—and hun- dreds of animals were cleaned and saved by wildlife rescue teams—but a much larger, unknown, number succumbed to the oil. What effects this mortality may have on populations in coming years is unclear. Following the Exxon Valdez spill in Alaska in 1989, populations of some species rebounded after several years, but populations of others have never recovered. Researchers are following the movements of some marine animals with radio transmitters to try to learn what effects the oil may have had.

As images of oil-coated marshes saturated the media, researchers wor- ried that widespread death of marsh grass would leave the shoreline vulner- able to severe erosion by waves. Louisi- ana has already lost many of its coastal wetlands to subsidence, dredging, sea

T H E S C I E N CE B E H I N D T H E S TO RY

Discovering the Impacts of the Gulf Oil Spill

Oil spills pollute marine and coastal environments Even if we can clean up air pollution from power plants, fossil fuels pollute water in many ways. What comes most readily to mind is the pollution that occurs when massive oil spills from tanker ships or drilling platforms foul coastal waters and beaches.

The Deepwater Horizon spill proved so difficult to con- trol because we had never had to deal with a spill so deep

underwater. It revealed that offshore drilling presents serious risks of environmental impact that may be difficult to address, even with our best engineering. As the oil spread through the Gulf of Mexico and washed ashore, the region suffered a wide array of impacts (see ENVISIONIT, p. 340). Of the countless animals killed, most conspicuous were birds, which cannot regulate their body temperature once their feathers become coated with oil. However, the underwater nature of the BP spill meant that unknown numbers of fish, shrimp, corals,

President Barack Obama echoed the perceptions of many Americans when he called the Deepwater Horizon oil spill “the worst environmental disas-ter America has ever faced.” But what has scientific research told us about the actual impacts of the Gulf oil spill? We don’t have all the answers, because the deep-water nature of the spill has

made it difficult for scientists to study. A great deal will remain unknown. Yet the intense and focused scientific response to the spill demonstrates the dynamic way in which science can assist society today.

Scientists’ first order of business as the spill proceeded was to determine how much oil was leaking and where it was going. Early estimates of the flow rate from BP and the U.S. government proved to be too low, and researchers eventually de- termined the rate as reaching 62,000 barrels per day. Using underwater imaging, aerial surveys, and shipboard water samples, researchers tracked the movement of oil up through the water column and across the Gulf. These data helped predict

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and other marine animals also died, affecting coastal and ocean ecosystems in complex ways. Marsh plants were also killed, and any resulting erosion of marshes puts New Orle- ans and other coastal cities at greater risk from storm surges and flooding. Gulf Coast fisheries, which supply much of the nation’s seafood, were hit hard by the spill, with thousands of fishermen and shrimpers put out of work. Beach tourism suffered, and economic and social impacts were expected to last for years. Throughout this process, scientists have been

studying aspects of the spill and its impact on the region’s people and natural systems (see THE SCIENCE BEHIND THE STORY, above).

As climate change melts sea ice in the Arctic, new ship- ping lanes are opening and nations are jockeying for position, hoping to stake claim to oil and gas deposits that lie beneath the seafloor in this region. Offshore drilling in Arctic waters, however, would pose severe pollution risks, because if a spill were to occur, icebergs, pack ice, storms, cold temperatures,

level rise, and silt capture by dams on the Mississippi River (p. 249). Fortu- nately, researchers found that oil did not penetrate to the roots of most plants, and that many oiled grasses were sending up new growth. Indeed, Louisiana State University researcher Eugene Turner said that loss of marsh- land in 2010 from the oil “pales in comparison” with marshland already lost each year due to other factors.

The ecological impacts of the spill had measurable impacts on people. The region’s mighty fisheries were shut down, forcing thousands of fishermen out of work. The government tested fish and shellfish for contamination and reopened fishing once they were found to be safe, but consumers did not want to buy Gulf seafood. Beach tourism remained low all summer as visitors avoided the region. Together, the losses in fishing and tour- ism totaled billions of dollars.

Stress and anxiety over economic losses affected people’s health, studies showed. Over one-third of parents told Columbia University researchers in a survey that their children had suffered physical or mental health effects as a result of the spill—and this figure increased to one-half for low-income residents. Other studies found rises in depression, headaches, respiratory problems, and domestic violence.

Scientists expect some impacts from the Gulf spill to be long-lasting. Oil from the similar Ixtoc blowout off Mexico’s coast in 1979 still lies in coast- al mangrove forests and in sediments near dead coral reefs. Fishermen there say it took years for catches to return to normal, and oysters have never come back. After the Amoco Cadiz tanker spill, it took seven years for oysters and other marine species to recover. In Alaska, oil from the Exxon Valdez spill remains embedded in beach sand, and researchers debate whether it is

best to try to remove it or to leave it undisturbed.

However, researchers agree on reasons to be hopeful about the Gulf’s recovery. One is that the Gulf’s warm and sunny climate speeds the natu- ral breakdown of oil. In hot sunlight, volatile components of oil evaporate from the surface and degrade in the water, so that fewer toxic compounds such as benzene, naphthalene, and toluene reach marine life. In addition, bacteria that consume hydrocarbons live in the Gulf’s waters, sediments, and marshes, because some oil seeps naturally from the seafloor, and leakage from platforms, tankers, and pipelines are common. Thus, whereas for other major spills, responders tried to apply

oil-eating bacteria or fertilize beaches to encourage bacterial growth, in the Gulf these microbes are already thriv- ing, giving the region a natural self- cleaning capacity.

Researchers are now conducting a wide range of scientific studies (see figure). New funding should help: BP has promised to provide half a bil- lion dollars for research over the next 10 years, which is 10 times what the federal government had been provid- ing before the spill. Answers to our many questions will come in gradually as long-term impacts become clear. Scientists can only hope that many findings will be happy ones and that the Gulf’s systems will recover more fully than expected.

WATER COLUMN AND SEDIMENTS • Water quality surveys • Sediment sampling • Transect surveys to detect oil • Oil plume modeling

FISH, SHELLFISH, AND CORALS • Population monitoring of adults and larvae • Surveys of food supply (plankton and invertebrates) • Tissue collection and sediment sampling • Testing for contaminants

BIRDS, TURTLES, MARINE MAMMALS • Air, land, and boat surveys • Radiotelemetry, satellite tagging, and acoustic monitoring • Tissue sampling • Habitat assessment

SHORELINES • Air and ground surveys • Habitat assessment • Measurements of subsurface oil

HUMAN USE • Air and ground surveys

AQUATIC VEGETATION • Air and coastal surveys

Wellhead

The effort to assess damage to natural resources from the Deepwater Horizon oil spill is the largest-ever undertaking of its kind. In this multi-pronged en- deavor, thousands of researchers are surveying habitats, collecting samples and testing them in the lab, tracking wildlife, monitoring populations, and more.

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➤

Cleaning oiled beaches

Oiled brown pelican

Oil slicks on surface

... where it fouled beaches, killed countless animals, and devastated fisheries and tourism.

Thousands of people threw themselves into the cleanup effort, but the spill’s impacts will last for years.

The Deepwater Horizon spill disgorged tens of millions of gallons of oil into the Gulf of Mexico ...

You Can Make a Difference

Volunteer for cleanups of oil spills in your region.

Urge policymakers to strengthen regulations on offshore drilling.

Limit your own oil consumption by driving less, driving a fuel-efficient car, eating local foods, reusing and recycling products, and supporting renewable energy.

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sand meters in radius) around a drill pad. As a result, fewer drill pads are needed, and the surface footprint of drilling is smaller.

The costs of alleviating the health and environmental impacts of fossil fuel extraction are generally not internal- ized in the market prices of fossil fuels. Instead, we all pay these external costs (p. 92) through medical expenses, costs of environmental cleanup, and impacts on our quality of life. Moreover, the prices we pay at the gas pump or on our monthly utility bill do not even cover the financial costs of fossil fuel production. Rather, fossil fuel prices have been kept inexpensive as a result of government subsidies to ex- traction companies (p. 108). Thus, we all pay extra for our fossil fuel energy through our taxes, generally without even realizing it.

Fossil fuel extraction has mixed consequences for local people For people who live in fossil-fuel-bearing regions, develop- ment and extraction can yield jobs and economic benefits, but can also result in pollution. In the Gulf of Mexico re- gion, oil and gas industries employ 107,000 people and con- tribute money toward local economies. However, far more people are employed in tourism, service industries, and fishing industries, which all were negatively affected by the Deepwater Horizon spill. Thus, single incidents can some- times overwhelm the economic benefits of fossil fuel devel- opment. Similar tradeoffs exist between jobs and environ- mental impact in mountaintop-mining areas of Appalachia (p. 240).

In most parts of the world where fossil fuels have been extracted, local residents have suffered pollution without the economic gains to compensate. When multinational corporations extract oil or gas in developing countries, paying those countries’ governments for access, the money often does not trickle down to the people who live where the extraction takes place. Moreover, oil-rich developing nations such as Ecuador, Venezuela, and Nigeria tend to have few environmental regulations, and existing regula- tions may go unenforced if a government does not want to risk losing the large sums of money associated with oil development.

In Ecuador, local people brought suit against Chevron for environmental and health impacts from years of oil extraction in the nation’s rainforests. An Ecuadorian court in 2011 found the oil company guilty and ordered it to pay $9.5 billion for cleanup—the largest-ever such judgment. However, Chevron succeeded in getting a U.S. court to issue an injunction, and the two sides are now tussling over jurisdiction. The complex legal battle is being watched internationally, as its outcome could set an influential precedent.

In Nigeria, the Shell Oil Company extracted $30 billion of oil from land of the native Ogoni people, yet the Ogoni still live in poverty, with no running water or electricity. Profits from the oil extraction went to Shell and to the military dic- tatorships of Nigeria. The development resulted in oil spills, noise, and constantly burning gas flares, all of which caused illness among people living nearby. Starting in 1962, Ogoni activist and leader Ken Saro-Wiwa fought for fair compensa-

and wintertime darkness would hamper response efforts. Frigid water temperatures would also slow the natural break- down of oil.

Fossil fuel use and extraction pollute in various ways Although large catastrophic oil spills have significant im- pacts on the marine environment, most water pollution from oil results from numerous non-point sources (pp. 265–266) to which all of our actions contribute (p. 267). Oil from auto- mobiles, homes, industries, gas stations, and businesses runs off roadways and enters rivers and wastewater facilities, being discharged eventually into the ocean. Oil can also contami- nate groundwater supplies when underground storage tanks leak. In addition, atmospheric deposition of pollutants from the combustion of fossil fuels exerts many impacts on fresh- water ecosystems (p. 291).

Extracting fossil fuels on land exerts environmental im- pacts as well. Mining coal causes water pollution through acid drainage (p. 238), habitat destruction, and a number of other environmental and social impacts (pp. 238, 240). At extrac- tion sites for coalbed methane (methane extracted from coal seams), groundwater is pumped out to free gas to rise, but salty groundwater dumped on the surface can contaminate soil and kill vegetation over large areas.

At many natural gas wells, gas is extracted by hydrau- lic fracturing, or “hydrofracking,” in which drillers fracture rock formations by injecting pressurized water mixed with sand and chemicals. The immense volumes of wastewater returned to the surface in this process are often laced with salts, radioactive elements such as radium, and toxic chemi- cals such as benzene picked up from deep underground. This wastewater is often sent to sewage treatment plants that are not designed to handle all the contaminants and that do not regularly test for radioactivity. This is currently causing con- cern in Pennsylvania, where a boom in natural gas extraction from the vast Marcellus Shale deposit is sending millions of gallons of drilling waste to treatment plants, which then re- lease their treated water into rivers that supply drinking wa- ter for people in Pittsburgh, Philadelphia, Harrisburg, and other cities.

To drill for oil or gas on land, road networks must be constructed, and many sites may be explored in the course of prospecting. The extensive infrastructure needed to support a full-scale drilling operation typically includes housing for workers, access roads, transport pipelines, waste piles for re- moved soil, and ponds to collect the toxic sludge that remains after oil is removed. These activities can pollute soil and wa- ter, fragment habitats, and disturb wildlife. All these impacts have been documented on the tundra of Alaska’s North Slope, where policymakers continue to debate whether to open the Arctic National Wildlife Refuge to drilling.

Fortunately, drilling technology is more environmentally sensitive than in the past. Directional drilling involves drill- ing wells in directions outward from a drilling pad, as drillers bore down vertically and then curve to drill horizontally. This allows extraction companies to follow horizontal layered de- posits to extract the most they can from them. It also allows drilling to reach a large underground area (up to several thou-

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sition, because they had long supported many of the region’s autocratic rulers. These rulers had facilitated Western access to oil, even as they suppressed democracy in their own so- cieties. The 2011 uprisings were only the most recent in a long history of events that have affected oil prices and global access to oil, stretching back through the U.S.-led wars in Iraq and the Iran-Iraq War of the 1980s to the 1973 OPEC embargo.

In response to the 1973 embargo, the U.S. government enacted a series of policies to reduce reliance on foreign oil. It urged oil companies to pursue secondary extraction at old oil wells. It established an emergency stockpile (which today stores one month’s worth of oil). It capped the price that do- mestic producers could charge for oil, funded research into renewable energy sources, and enacted conservation meas- ures we will discuss below. The new U.S. policies also called for developing additional domestic sources, including off- shore oil from the Gulf of Mexico. Since then, the desire to re- duce reliance on foreign oil by boosting domestic production has driven the expansion of offshore drilling into deeper and deeper water. It has also repeatedly driven a proposal to open the Arctic National Wildlife Refuge on Alaska’s North Slope to drilling, despite critics’ charges that drilling there would spoil America’s last true wilderness while doing little to boost the nation’s oil supply.

Drill, Baby, Drill? Do you think the United States should open more of its offshore waters to oil extraction? Would the benefits exceed the potential costs? Should we place limits on how far

from shore drilling should take place? Should the gov- ernment regulate offshore drilling more strongly? Give reasons for your answers.

tion to the Ogoni. After years of persecution by the Nigerian government, Saro-Wiwa was arrested in 1994, given a trial universally regarded as a sham, and put to death by military tribunal.

Dependence on foreign energy affects the economies of nations Putting all of one’s eggs in one basket is always a risky strat- egy. Because virtually all our modern technologies and services depend in some way on fossil fuels, we are vulner- able to supplies’ becoming unavailable or costly. Nations that lack adequate fossil fuel reserves of their own are espe- cially vulnerable (FIGURE 15.13). Since its 1970 oil produc- tion peak, the United States has relied more and more on foreign energy, and today the nation imports two-thirds of its crude oil.

Such reliance means that seller nations can control en- ergy prices, forcing buyer nations to pay more as supplies dwindle. This became clear in 1973, when the Organization of Petroleum Exporting Countries (OPEC) resolved to stop selling oil to the United States. The predominantly Arab na- tions of OPEC opposed U.S. support of Israel in the Arab- Israeli Yom Kippur War and sought to raise prices by re- stricting supply. The embargo created panic in the West and caused oil prices to skyrocket (FIGURE 15.14), spurring infla- tion. Fear of oil shortages drove American consumers to wait in long lines at gas pumps. More recently, when Hurricanes Katrina and Rita slammed into the Gulf Coast in 2005, they damaged refineries and offshore platforms, causing oil and gas prices to spike.

With the majority of global oil reserves located in the politically volatile Middle East, crises in this region of the world are a constant concern for U.S. policymakers. The democratic street uprisings of 2011 that began in Tunisia and Egypt and spread across the region put leaders of the United States and other Western nations in an awkward po-

Production Consumption

M ill

io n b

ar re

ls o

f o il

p er

d ay

Jap an

Ge rm

an y

Un ite

Sta tes

Ira n

Sa ud

Ar ab

FIGURE 15.13  Japan, Germany, and the United States are among nations that consume far more oil than they produce. Iran and Saudi Arabia produce more oil than they consume and are able to export oil to high-consumption countries. Data are for 2010, from U.S. Energy Information Administration and British Petroleum.

100

130

140

120

110

Year 1950 1960 1970 1980 1990 2000 2010

C ru

d e

o il

p ri ce

s (U

.S .

d o

lla rs

p er

b ar

re l)

OPEC oil embargo

Iranian Revolution

Gulf War

U.S. invades Iraq

Recession

Hurricanes Katrina

& Rita

Dollar value adjusted for inflation

Dollar value of the day

FIGURE 15.14  World oil prices have gyrated greatly over the decades, often because of political and economic events in oil- producing countries. The greatest price hikes in recent times have resulted from wars and unrest in the oil-rich Middle East. Data from U.S. Energy Information Administration.

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serve energy, through lifestyle changes that reduce energy use, and through technological advances that improve efficiency.

ENERGY EFFICIENCY AND CONSERVATION Until our society makes the transition to renewable energy sources, we will need to find ways to minimize use of our dwindling fossil fuel resources. Energy efficiency describes the capacity to obtain a given result or amount of output while using less energy input. Energy conservation describes the practice of reducing energy use. Because greater efficiency al- lows us to reduce energy use, efficiency is one primary means toward conservation. Efficiency and conservation allow us to extend the lifetimes of our nonrenewable energy supplies, to be less wasteful, and to reduce our environmental impact.

Personal choice and efficient technologies are two routes to conservation As individuals, we can make conscious choices to reduce our own energy consumption by driving less, turning off lights when rooms are not being used, dialing down thermostats,

Despite all these policies, U.S. demand for oil has remained high enough that the nation has needed to import more and more each year. The United States has diversified its foreign sources, however, and today receives most oil from non–Mid- dle Eastern nations, including Canada, Mexico, Venezuela, and Nigeria.

How will we convert to renewable energy? Fossil fuels are not a sustainable long-term solution to our en- ergy needs. Fossil fuels are limited in supply, and their use has health, environmental, political, and socioeconomic conse- quences (FIGURE 15.15). Concern over these issues is a prime reason many scientists, environmental advocates, business- people, and policymakers are looking to shift to clean and renewable sources of energy that exert less impact on natu- ral systems and human health. Many nations are moving far faster than the United States. France relies on nuclear power for its electricity needs, Germany is investing in solar power (pp. 354–355), and China is forging ahead and developing multiple renewable energy technologies.

As we make the transition to renewable energy sources, it will benefit us to prolong the availability of fossil fuels. We can prolong our access to fossil fuels by instituting measures to con-

Solutions

As you progress through this chapter, try to identify as many solutions to our reliance on and depletion of fossil fuels as you can. What could you personally do to help address this issue? Consider how each action or solution might affect items in the concept map above.

Causes Consequences

Low prices

Social disruption

Health impacts

Economic loss

Pollution of air, water, soil

Economic depression

Attempt to shift quickly to renewable

energy sources

End to globalization; societies become

localized

Depletion of fossil fuels

Degradation of ecosystems

Government subsidies

Human population growth Limited non-

renewable supplies

Poor fuel efficiency in autos

More uses (plastics, etc.)

Failure to develop other energy sources

Growth in per capita consumption

No accounting for external costs

Economic and political vulnerability

Extraction impacts

if this fails, then...

Global climate change

Greenhouse gas emissions

Reliance on fossil fuels

FIGURE 15.15  Our reliance on, and depletion of, fossil fuels has many causes (ovals on left) and many consequences (boxes on right). Arrows in this concept map lead from causes to consequenc- es. Note that items grouped within outlined boxes do not neces- sarily share any special relationship; the outlined boxes are merely intended to streamline the figure.

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program, which labels refrigerators, dishwashers, and other appliances for their energy efficiency, has helped to reduce U.S. per-person home electricity use below what it was in the 1970s. For the consumer, studies show that savings on utility bills readily offset the higher costs of energy-efficient appli- ances.

Automotive technology represents perhaps our best opportunity to save large amounts of fossil fuels fairly eas- ily. We can accomplish this with alternative-technology vehicles such as electric cars, electric/gasoline hybrids (FIGURE 15.16), or vehicles that use hydrogen fuel cells (pp. 375–376). Among electric/gasoline hybrids, current U.S. models of the Toyota Prius and the Chevrolet Volt aver- age fuel economy ratings of 50 miles per gallon (mpg) and 60 mpg, respectively—two to three times better than the average American car. Even without alternative vehicles, however, we already possess the means to increase fuel ef- ficiency for gasoline-powered vehicles by using lightweight materials, continuously variable transmissions, and more- efficient gasoline engines.

Automobile fuel efficiency is a key to conservation Among the measures enacted by the U.S. government in re- sponse to the OPEC embargo of 1973–1974 were a mandated increase in the mile-per-gallon (mpg) fuel efficiency of au- tomobiles and a reduction in the national speed limit to 55 miles per hour. Over the next three decades, however, many of the conservation initiatives that followed the 1973–1974 oil crisis were abandoned. Without high market prices and an immediate threat of shortages, people lacked economic motivation to conserve. Government funding for research into alternative energy sources dwindled, speed limits rose, and U.S. policymakers repeatedly failed to raise the cor- porate average fuel efficiency (CAFE) standards, which set benchmarks for auto manufacturers to meet. The average fuel efficiency of new vehicles fell from 22.0 mpg in 1987 to 19.3 mpg in 2004 (as sales of sport-utility vehicles increased relative to sales of cars).

and cutting back on the use of energy-intensive machines and appliances. Many European nations use less energy per capita than the United States, yet enjoy equivalent standards of living. This indicates that U.S. citizens could reduce their energy consumption without diminishing their quality of life. Moreover, for any given individual or business, reducing energy consumption can save money while helping to con- serve resources.

As a society, we can conserve energy by developing tech- nologies and strategies to make our energy-consuming de- vices and processes more efficient. Currently, more than two- thirds of the fossil fuel energy we use is simply lost, as waste heat, in automobiles and power plants. The United States burns through twice as much energy per dollar of Gross Domestic Product (GDP) as do most other industrialized nations. However, the good news is that over the past three decades the United States has decreased its energy use per dollar of GDP by about 50%. Given such tremendous gains in efficiency, we should be able to make still-greater progress in the future.

We can improve the efficiency of power plants through co- generation, in which excess heat produced during electricity generation is captured and used to heat nearby workplaces and homes and to produce other kinds of power. Cogenera- tion can almost double the efficiency of a power plant.

In homes, offices, and public buildings, a significant amount of heat is needlessly lost in winter and gained in summer because of poor design and inadequate insulation. Improvements in design can reduce the energy required to heat and cool buildings (p. 408). Such improvements may in- volve passive solar design (p. 364), better insulation, a build- ing’s location, the vegetation around it, and even the color of its roof (light colors keep buildings cooler by reflecting the sun’s rays).

Consumer products such as lightbulbs and appliances have been reengineered through the years to enhance effi- ciency. Compact fluorescent bulbs are far more efficient than incandescent light bulbs, and many governments are phasing out incandescent bulbs for this reason; the U.S. phase-out is scheduled to be complete in 2014. The U.S. EPA’s Energy Star

Gasoline- powered engine

Generator2

Electric motor3 Power split device

4 5 Batteries Fuel tank6

FIGURE 15.16  A hybrid car, such as the Toyota Prius diagrammed here, uses a small, clean, and efficient gasoline-powered en- gine � to produce power that the genera- tor � can convert to electricity to drive the electric motor �. The power split device � integrates the engine, generator, and motor, serving as a continuously variable transmission. The car automatically switches between all-electrical power, all-gas power, and a mix of the two, depending on the demands being placed on the engine. Typically, the motor provides power for low-speed city driving and adds extra pow- er on hills. The motor and generator charge a pack of nickel-metal-hydride batteries �, which can in turn supply power to the motor. Energy for the engine comes from gasoline carried in a typical fuel tank �.

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nomic activity and saving jobs during a severe recession. The popular “Cash for Clunkers” program—formally named the Consumer Assistance to Recycle and Save (CARS) Act— paid Americans $3,500 or $4,500 each to turn in old vehi- cles and purchase newer, more fuel-efficient ones. The $3 billion program subsidized the sale or lease of 678,000 ve- hicles averaging 24.9 mpg that replaced vehicles averaging 15.8 mpg. It is estimated that 824 million gallons of gasoline will be saved as a result, preventing 9 million metric tons of greenhouse gas emissions and creating social benefits worth $278 million.

The rebound effect cuts into efficiency gains Energy efficiency is a vital pursuit, but it may not always save as much energy as we expect. This is because gains in effi- ciency from better technology can be partly offset if people engage in more energy-consuming behavior as a result. For instance, a person who buys a fuel-efficient car may choose to drive more because he or she feels it’s OK to do so now that less gas is being used per mile. This phenomenon is called the “rebound effect,” and studies indicate that it is widespread. In some instances, the rebound effect may completely erase ef- ficiency gains, and attempts at energy efficiency may end up actually causing greater energy consumption! As our society pursues energy efficiency in more and more ways, this will be an important factor to consider.

Nonetheless, efficiency will play a necessary role in the conservation efforts we make toward reducing energy use. It is often said that reducing our energy use is equivalent to finding a new oil reserve. Some estimates hold that effective conservation and efficiency in the United States could save 6 million barrels of oil a day—nearly the amount we gain from all offshore drilling—while also reducing the negative impacts of fossil fuel extraction and use. Indeed, conserving energy is better than finding a new reserve, because it lessens health and environmental impacts while extending our access to fossil fu- els. However, regardless of how much we conserve, we will still need energy. Among the alternatives to fossil fuels for our energy economy is nuclear power.

NUCLEAR POWER Nuclear power occupies an odd and conf licted position in our modern debate over energy. Free of the air pollution produced by fossil fuel combustion, it has long been put forth as an environmentally friendly alternative to fossil fuels. Yet nuclear power’s great promise has been clouded by nuclear weaponry, the dilemma of radioactive waste dis- posal, and the long shadow of Chernobyl and other power plant accidents. As a result, public safety concerns and the costs of addressing them have constrained nuclear power’s spread.

First developed commercially in the 1950s, nuclear power experienced most of its growth during the 1970s and 1980s. The United States generates the most electricity from nuclear power—over a quarter of the world’s production— yet only 20% of U.S. electricity comes from nuclear power. A

Since then, however, fuel economy has climbed up to 22.5 mpg in 2010 (FIGURE 15.17). Much of this recent rise in fuel efficiency occurred after Congress passed legislation in 2007 mandating that automakers raise average fuel efficiency to 35 mpg by the year 2020. This was a substantial advance, yet even after this boost, American automobiles will still lag behind the vehicles of most other developed nations. The fuel efficiency of European and Japanese cars is nearly twice that of U.S. cars and is slated to keep improving.

The United States has also kept its taxes on gasoline ex- tremely low, relative to other nations. Americans pay two to three times less per gallon of gas than drivers in many Euro- pean countries, for example. As a result, U.S. gasoline prices do not account for the substantial external costs (p. 92) that oil production and consumption impose on society. The low prices also diminish our economic incentive to conserve.

More Miles, Less Gas If you drive an automobile, what gas mileage does it get? How does it compare to the vehicle averages in Figure 15.17? If your vehicle’s fuel efficiency were 10 mpg

greater, and if you drove the same amount, how many gallons of gasoline would you no longer need to purchase each year? How much money would you save?

Do you think the U.S. government should mandate further increases in the CAFE standards? Should the gov- ernment raise taxes on gasoline sales to encourage con- sumers to conserve energy? What effects (on economics, on health, and on environmental quality, for instance) might these steps have?

In 2009, Congress and the Obama administration sought to improve automobile fuel efficiency while stimulating eco-

25 Cars

A ve

ra g

e fu

el e

ff ic

ie n

cy (m

ile s

p er

g al

lo n

)

Trucks

Both cars and trucks20

10 1970 1975 1980 1985

Model year

1990 1995 2000 2005 2010

FIGURE 15.17  Fuel efficiency for automobiles in the United States rose dramatically in the late 1970s as a result of legislative mandates, but it then stagnated due to a lack of further laws for improved fuel economy. Recent legislation is now improving it again. Data from U.S. Environmental Protection Agency, 2010. Light-duty automotive technology, carbon dioxide emissions, and fuel economy trends:

1975 through 2010.

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number of other nations rely more heavily on nuclear power (TABLE 15.6).

Fission releases nuclear energy in reactors to generate electricity Strictly defined, nuclear energy is the energy that holds to- gether protons and neutrons (p. 26) within the nucleus of an atom. We harness this energy by converting it to thermal energy, which can then be used to generate electricity. The reaction that drives the release of nuclear energy in power plants is nuclear fission, the splitting apart of atomic nuclei (FIGURE 15.18). In fission, the nuclei of large, heavy atoms,

such as uranium or plutonium, are bombarded with neu- trons. Ordinarily, neutrons move too quickly to split nu- clei when they collide with them, but if neutrons are slowed down they can break apart nuclei. Each split nucleus emits energy in the form of heat, light, and radiation, and it also releases multiple neutrons. These neutrons (two to three in the case of uranium-235) can in turn bombard other nearby uranium-235 (235U) atoms, resulting in the positive feedback (p. 22) of a self-sustaining chain reaction.

If not controlled, this chain reaction becomes a runaway process of positive feedback—the process that creates the explosive power of a nuclear bomb. Inside a nuclear power plant, however, fission is controlled so that only one of the two or three neutrons emitted with each fission event goes on to induce another fission event. In this way, the chain reaction maintains a constant output of energy at a control- led rate.

For fission to begin in a nuclear reactor, the neutrons bombarding uranium are slowed down with a substance called a moderator, most often water or graphite. As fission proceeds, it becomes necessary to soak up the excess neutrons produced when uranium nuclei divide, so that on average only a single neutron from each nucleus goes on to split another nucleus. For this purpose, control rods, made of a metallic alloy that ab- sorbs neutrons, are placed into the reactor among the water- bathed fuel rods of uranium. Engineers move these control rods into and out of the water to maintain the fission reaction at the desired rate. All this takes place within the reactor core and is the first step in the electricity-generating process of a nuclear power plant (FIGURE 15.19).

Nuclear energy comes from processed and enriched uranium We use the element uranium for nuclear power because its atoms are radioactive, emitting subatomic particles and high- energy radiation as they decay into a series of daughter iso- topes (p. 26). We obtain uranium from various minerals in naturally occurring uranium ore (ore is rock that contains minerals of economic interest [p. 236]). Uranium-containing minerals are uncommon, and uranium ore is in finite sup- ply, so nuclear power is generally considered a nonrenewable energy source.

In the uranium ore we mine from the ground, over 99% of the uranium occurs as the isotope uranium-238, whereas less than 1% is uranium-235 (which has three fewer neutrons). Because 238U does not emit enough neutrons to maintain a chain reaction when fissioned, we use 235U for commercial nuclear power. As a result, we must process the ore we mine to enrich the concentration of 235U to at least 3%. The enriched uranium is formed into pellets of uranium dioxide (UO2), which are incorporated into the fuel rods used in reactors.

After several years in a reactor, enough uranium has decayed so that the fuel no longer generates adequate en- ergy, and it must be replaced with new fuel. In some coun- tries, the spent fuel is reprocessed to recover the remaining usable energy. However, this is costly relative to the low prices of uranium on the world market in recent years, so

TABLE 15.6 Top Producers of Nuclear Power

Nation

Nuclear power

produced* Number

of reactors†

Percentage of electricity from nuclear power†

United States 807.1 104 19.6

France 410.1 58 74.1

Japan 280.3 50 29.2

Russia 159.4 32 17.1

South Korea 141.9 21 32.2

Germany 133.0 17 28.4

Canada 85.5 18 15.1

Ukraine 84.0 15 48.1

China 71.0 14 1.8

Spain 59.3 8 20.1 *In gigawatt-hours, 2011 data, from the World Nuclear Association. †2010 data, from the International Atomic Energy Agency.

Neutron

Proton

Nucleus of 235Uranium

Energy

Fission fragment (krypton, for example)

Fission fragment (barium, for example)

Free neutrons

FIGURE 15.18  In nuclear fission, the nucleus of an atom of uranium-235 is bombarded with a neutron. The collision splits the uranium atom into smaller atoms and releases two or three neutrons, along with energy in the form of heat, light, and radia- tion. The neutrons can continue to split uranium atoms and set in motion a runaway chain reaction, so engineers at nuclear plants must absorb excess neutrons with control rods to regulate the rate of the reaction.

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Cooling tower

Fission occurs in the reactor core, where fuel rods are submerged in water. The water slows neutrons in order to initiate a chain reaction in uranium-235 in the fuel rods, while control rods absorb excess neutrons to regulate that reaction.

Water heated by fission circulates through the primary loop, which is pressurized to prevent boiling.

Cold water from the cooling tower circulates within the cooling loop, condensing steam in the secondary loop and converting it to liquid water, which then returns to be boiled by the heated pressurized water of the primary loop.

Water heated by fission in the primary loop boils water in the secondary loop, creating steam.

The steam drives turbines, which generate electricity.

Generator

Cooling loopCondenser

Turbine

Cooling tower

Steam Moderator

(water)

Primary loop

Secondary loop

Reactor core

Reactor vessel

Control rod

Steam generator

Nuclear fuel (uranium)

Containment building

FIGURE 15.19  In a pressurized light water reactor, the most common type of nuclear reactor, uranium fuel rods are placed in water, which slows neutrons so that fission can occur �. Control rods that can be moved into and out of the reactor core absorb excess neutrons to regulate the chain reaction. Water heated by fission circulates through the primary loop � and warms water in the secondary loop, which turns to steam �. Steam drives tur- bines, which generate electricity �. The steam is then cooled in the cooling tower by water from an adjacent river or lake and returns to the containment building �, to be heated again by heat from the primary loop.

most spent fuel has been disposed of as radioactive waste (p. 392).

Nuclear power delivers energy more cleanly than fossil fuels Using fission, nuclear power plants generate electricity with- out creating the air pollution from stack emissions that fossil fuels do. After considering all the steps involved in building plants and generating power, researchers with the Interna- tional Atomic Energy Agency (IAEA) have calculated that nuclear power releases 4–150 times fewer emissions than fos- sil fuel combustion. IAEA scientists estimate that at current global levels of use, nuclear power helps us avoid emitting 600 million metric tons of carbon each year, equivalent to 7% of global greenhouse gas emissions.

Nuclear power has additional advantages over fossil fu- els—coal, in particular. For residents living downwind from power plants, scientists calculate that nuclear power poses far fewer chronic health risks from pollution than does fossil fuel combustion. And because uranium generates far more power than coal by weight or volume, less of it needs to be mined, so uranium mining causes less damage to landscapes and gener- ates less solid waste than coal mining. Moreover, in the course of normal operation, nuclear power plants are safer for work- ers than coal-fired plants.

Nuclear power also has drawbacks. One is that the waste it produces is radioactive, and arranging for safe disposal of

this waste is challenging. The second main drawback is that if an accident occurs at a power plant, or if a plant is sabotaged, the consequences can potentially be catastrophic.

Given this mix of advantages and disadvantages (FIG- URE 15.20), most governments (although not necessarily most citizens) have judged the good to outweigh the bad, and today the world has 441 operating nuclear plants in 30 nations.

Choose Your Risk Consult Figure 15.20 on the next page. Given the choice of living next to a nuclear power plant or living next to a coal-fired power plant, which would you choose? What

would concern you most about each option?

Nuclear power poses small risks of large accidents Although nuclear power delivers energy more cleanly than fossil fuels, the possibility of catastrophic accidents has spawned a great deal of public anxiety over nuclear power. Three events have been most inf luential in shaping public opinion about nuclear energy: Three Mile Island in the Unit- ed States; Chernobyl, the world’s most severe accident; and most recently, Fukushima Daiichi following the 2011 Japa- nese earthquake and tsunami.

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Three Mile Island The first event took place at the Three Mile Island plant in Pennsylvania in 1979. Through a com- bination of mechanical failure and human error, coolant water drained from the reactor vessel, temperatures rose in- side the reactor core, and metal surrounding the uranium fuel rods began to melt, releasing radiation. This process is termed a meltdown, and at Three Mile Island it proceeded through half of one reactor core. Area residents stood ready to be evacuated as the nation held its breath, but fortunately most radiation remained trapped inside the containment building.

Once this accident was brought under control, the dam- aged reactor was shut down, and multi-billion-dollar cleanup efforts stretched on for years. Three Mile Island is best regarded as a near miss; the emergency could have been far worse had the meltdown proceeded through the entire stock of urani- um fuel or had the containment building not contained the radiation.

Chernobyl In 1986, an explosion at the Chernobyl plant in Ukraine (part of the Soviet Union at the time) caused the most severe nuclear power plant accident the world has seen. Engineers had turned off safety systems to conduct tests, and human error, combined with unsafe reactor design, led to explosions that destroyed the reactor and sent clouds of radioactive debris billowing into the atmosphere. Atmos- pheric currents carried radioactive fallout across much of

the Northern Hemisphere, particularly Ukraine, Belarus, and parts of Russia and Europe. For 10 days, radiation es- caped from the plant while emergency crews risked their lives putting out fires. Most residents of the surrounding countryside remained at home for these 10 days, exposed to radiation, before the Soviet government belatedly began evacuating more than 100,000 people.

In the months and years afterwards, workers removed ir- radiated materials, scrubbed buildings and roads, and erected a gigantic concrete sarcophagus around the demolished re- actor (FIGURE 15.21). However, the landscape for at least 30 km (19 mi) around the plant remains contaminated, the de- molished reactor is still full of dangerous fuel and debris, and radioactivity leaks from the hastily built and quickly deterio- rating sarcophagus. Today an international team is trying to build a larger sarcophagus around the original one to prevent a re-release of radiation.

The accident at Chernobyl killed 31 people directly and sickened or caused cancer in thousands more. Exact numbers are uncertain because of inadequate data and the difficulty of determining long-term radiation effects. Health authorities estimate that most of the over 5,000 cases of thyroid cancer diagnosed in people who were children at the time resulted from radioactive iodine spread by the accident. Estimates for the total number of cancer cases attributable to Chernobyl, past and future, vary widely, but an international consensus effort 20 years after the event estimated that radiation raised

Greenhouse gas emissions

Type of Impact Coal Nuclear

Considerable emissions None from plant operation; much less than coal over the entire life cycle

Land and ecosystem disturbance from mining

Extensive, on surface or underground Less extensive

Other air pollutants Sulfur dioxide, nitrogen oxides, particulate matter, and other pollutants

No pollutant emissions

Radioactive emissions No appreciable emissions Possibility of dangerous emissions if severe accident occurs

Occupational health among workers

More known health problems and fatalities Fewer known health problems and fatalities

Health impacts on nearby residents Air pollution impairs health

No appreciable known health impacts under normal operation

Effects of accident or sabotage No widespread effects Potentially catastrophic widespread effects

Solid waste More generated Less generated

Radioactive waste None Radioactive waste generated

Fuel supplies remaining Should last several hundred more years Uncertain; supplies could last longer or shorter than coal supplies

Environmental Impacts of Coal-fired and Nuclear Power

FIGURE 15.20  Coal-fired power plants and nuclear power plants pose very different risks and impacts to human health and the environment. This chart compares the major impacts of each mode of electricity generation. For each type of impact, a red box indicates the more severe impact.

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the cancer rate among exposed people by up to a few per- cent, resulting in up to several thousand fatal cancer cases.

Fukushima Daiichi On March 11, 2011, a magnitude 9.0 earthquake struck eastern Japan and sent an immense tsuna- mi roaring onshore (pp. 232, 234). Over 23,000 people were killed and many thousands of buildings were destroyed. This natural disaster affected the operation of several of Japan’s nuclear plants, most notably the Fukushima Daiichi nuclear power plant. Here, the earthquake shut down power and the tsunami f looded the plant’s emergency power generators. Without electricity, workers could not use moderators and control rods to cool the uranium fuel, and the fuel began to overheat as fission proceeded, uncontrolled.

Amid the damage and chaos across the region, help was slow to arrive, and workers had to begin flooding the reactors with seawater in a desperate effort to prevent meltdowns. Sev- eral explosions and fires occurred over the next few days, and eventually three reactors experienced full meltdowns, while the plant’s other three reactors were seriously damaged. Parts of the plant remained inaccessible for months because of ra- dioactive water, and it is estimated that it will require years or decades to fully clean up the site.

Radioactivity was released during and after these events at levels lower than but comparable to those from Chernobyl. Much of it spread by air or water into the Pacific Ocean, and trace amounts were detected around the world. Thousands of residents of areas near the plant were evacuated and screened for radiation (FIGURE 15.22), while restrictions were placed on food and water from the region. At the time of this writing,

releases of radioactivity continued, and long-term health ef- fects on the area’s people remain uncertain.

The disaster at Fukushima Daiichi could probably have been avoided had the emergency generators not been located in the basement where a tsunami could flood them. And the design of most modern reactors is safer than Chernobyl’s. Yet natural disasters and human error will always pose risks—and as plants age, they require more maintenance and become less safe. Moreover, radioactive material could be stolen from plants and used in terrorist attacks. This possibility is espe- cially worrisome in the cash-strapped nations of the former Soviet Union, where hundreds of former nuclear sites have gone without adequate security for years. In a cooperative in- ternational agreement, the U.S. government has been buying up some of this material and diverting it to peaceful use in power generation.

Waste disposal remains a problem Even if nuclear power generation could be made completely safe, we would still be left with the conundrum of what to do with spent fuel rods and other radioactive waste, which will continue emitting radiation for thousands of years. Current- ly, such waste is held in temporary storage at nuclear power plants. Spent fuel rods are sunken in pools of cooling water or encased in thick casks of steel, lead, and concrete to minimize radiation leakage.

In total, U.S. power plants are storing over 60,000 metric tons of high-level radioactive waste—enough to fill a football field to the depth of 6 m (20 ft)—as well as much more low- level radioactive waste. This waste is held at more than 120 sites spread across 39 states (FIGURE 15.23). A 2005 National Academy of Sciences report judged that most of these sites were vulnerable to terrorist attacks. Over 161 million U.S. citi- zens live within 125 km (75 mi) of temporarily stored waste.

FIGURE 15.22  A Japanese child evacuated from the Fukushima area is screened for radiation two weeks after the nuclear disaster that followed Japan’s devastating earthquake and tsunami. Radiation exposure can have serious long-term health effects.

FIGURE 15.21  The world’s worst nuclear power plant accident unfolded in 1986 at Chernobyl, in present-day Ukraine (then part of the Soviet Union). As part of the extensive cleanup operation, the destroyed reactor was encased in a massive concrete sarcophagus to contain further radiation leakage.

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Because storing waste at many dispersed sites creates a large number of potential hazards, nuclear waste managers would prefer to send all waste to a central repository that can be heavily guarded. In the United States, the multiyear search homed in on Yucca Mountain, a remote site in the desert of southern Nevada, 160 km (100 mi) from Las Vegas. Choice of this site followed extensive study by government scientists, and $13 billion was spent on its development, although Nevadans were not happy about the choice. In 2010 as the site was await- ing approval from the Nuclear Regulatory Commission, Presi- dent Barack Obama’s administration ended support for the project. However, some Congresspeople, agencies, and state governments are challenging this decision, and as of 2011 the issue remains unresolved. Without Yucca Mountain, the Unit- ed States has no place designated to dispose of its radioactive waste from commercial nuclear power plants, so this waste will remain at its numerous current locations across the country.

At Yucca Mountain, waste would be stored in a network of tunnels 300 m (1,000 ft) underground, yet 300 m (1,000 ft) above the water table (FIGURE 15.24). Scientists and policy- makers chose the Yucca Mountain site because they deter- mined that it is remote and unpopulated, has minimal risk of earthquakes, receives little rain that could cause radioactivity to percolate down into the groundwater, has a deep water ta- ble atop an isolated aquifer, and is on federal land that can be protected from sabotage. However, some scientists, antinu- clear activists, and concerned Nevadans have challenged these conclusions.

Another concern with any centralized repository is that waste would need to be transported there from the 120-plus current storage areas and from current and future nuclear plants and military installations. Because this would involve many thousands of shipments by rail and truck across hun-

dreds of public highways through almost every state of the union, some people worry that the risk of an accident or of sabotage is unacceptably high.

How to Store Waste? Which do you think is a better option—to transport nuclear waste cross-country to a single repository or to store it permanently at numerous power plants and

military bases scattered across the nation? Would your opinion be affected if you lived near the repository site? Near a power plant? On a highway route along which waste is transported?

Multiple dilemmas have slowed nuclear power’s growth Dogged by concerns over waste disposal, safety, and expen- sive cost overruns, nuclear power’s growth has slowed. Since the late 1980s, nuclear power has grown by 2.5% per year worldwide, about the same rate as electricity generation overall. Public anxiety in the wake of Chernobyl made utili- ties less willing to invest in new plants. So did the enormous expense of building, maintaining, operating, and ensuring the safety of nuclear facilities. Almost every nuclear plant has turned out to be more expensive than expected. In addi- tion, plants have aged more quickly than expected because of problems that were underestimated, such as corrosion in coolant pipes. The plants that have been shut down—well over 100 around the world to date—have served on average less than half their expected lifetimes. Moreover, shutting

Canisters of radioactive waste are shipped to the site

Radioactive waste is placed in a multilayered steel storage container and sent underground

Containers are stored along the tunnels

Yucca Mountain

Processing site

Tunnel system

Storage container

Water table

Ramp to tunnels

Container

300 m (1,000 ft)

FIGURE 15.24  Yucca Mountain, in a remote part of Nevada, was being developed as the central repository site for all commercial nuclear waste in the United States until support was withdrawn in 2010. Waste was to be buried in a network of tunnels deep under- ground, yet still high above the water table.

>1,000

Metric tons of spent fuel

101–1,000 <1–100 0

NV UT COCO

AZ CA

HI AK

ID WY

MT ND MN WI

LA MS AL

GA SC NC

VA WVOH

MD DE

MA NY

VT NH

IN KY

MI SD SD

NE NJ

RI CT

FIGURE 15.23  High-level radioactive waste from civilian reac- tors is currently stored at over 120 sites in 39 states across the United States. In this map, dots indicate storage sites, and the four shades of color indicate the total amount of waste stored in each state. Slightly different classifications of waste mean that some states shaded white show storage sites for certain types of waste. Data from Office of Civilian

Radioactive Waste Management, U.S. Department of Energy; and Nuclear

Energy Institute, Washington, D.C.

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T E S T I N G Y O U R C O M P R E H E N S I O N 1. Why are fossil fuels our most prevalent source of energy

today? Why are they considered nonrenewable sources of energy? How are fossil fuels formed?

2. Describe how net energy differs from energy returned on investment (EROI). Why are these concepts important when evaluating energy sources?

3. Describe how coal is used to generate electricity. Now, describe how we create petroleum products. Provide ex- amples of several of these products.

4. Why do many experts think we are about to pass the glo- bal production peak for oil? What consequences might there be for our society if we do not shift soon to renew- able energy sources?

5. Describe three environmental impacts of fossil fuel pro- duction and consumption. What impacts have resulted from drilling for oil offshore in the Gulf of Mexico?

6. Give an example of clean coal technology. Now describe how carbon capture and storage is intended to work.

7. Describe one specific example of how technological ad- vances can improve energy efficiency. Now describe one specific action you could take to conserve energy.

8. Describe how nuclear fission works. How do nuclear plant engineers control fission and prevent a runaway chain reaction?

9. In terms of greenhouse gas emissions, how does nuclear power compare to coal, oil, and natural gas?

10. In what ways did the events at Three Mile Island, Cher- nobyl, and Fukushima Daiichi differ from one another? What consequences resulted from each of these inci- dents? Now list several concerns about the disposal of radioactive waste. What has been done so far about disposing of radioactive waste?

S E E K I N G S O L U T I O N S 1. What impacts might you expect on your lifestyle once

our society arrives at peak oil? What lessons do you think we can take from the conservation methods adopt- ed by the United States in response to the “energy crisis” of 1973–1974? What steps do you think we should take to avoid energy shortages in a post-peak-oil future?

2. Describe and compare the environmental and social im- pacts of coal and oil extraction and consumption. What

steps could governments, industries, and individuals take to reduce these impacts?

3. Nuclear power has by now been widely used for over four decades, and the world has experienced only two major accidents (Chernobyl and Fukushima Daiichi) respon- sible for any significant number of injuries or deaths. Would you call this a good safety record? Should we maintain, decrease, or increase our reliance on nuclear

➤ CONCLUSION Over the past 200 years, fossil fuels have helped us build the complex industrialized societies we enjoy today. However, we are now approaching a turning point in history: Our produc- tion of fossil fuels will begin to decline. We can respond to this new challenge by encouraging conservation and develop- ing alternative energy sources. Or we can continue our cur- rent dependence on fossil fuels and wait until they near de- pletion before we try to develop new technologies and ways of life. The path we choose will have far-reaching consequences

for human health and well-being, for Earth’s climate, for our environment, and for the stability and progress of our civilization.

Nuclear power showed promise to be a pollution-free and highly efficient form of energy. However, high costs and public fears over safety in the wake of accidents have stalled its growth. Nuclear power will likely be part of our future en- ergy economy, but we will need to turn to renewable energy sources as well.

down, or decommissioning, a plant can sometimes be more expensive than the original construction.

As a result of these economic issues, electricity from nu- clear power today remains more expensive than electricity from coal and other sources. Governments are still subsidiz- ing nuclear power to keep electricity costs to ratepayers down, but many private investors lost interest long ago. Nonetheless, nuclear power remains one of the few currently viable alterna- tives to fossil fuels with which we can generate large amounts of electricity in short order. This is why an increasing number of environmental advocates propose expanding U.S. nuclear

capacity using a new generation of reactors designed to be safer and less expensive. Indeed, nuclear power was beginning to experience a bit of a renaissance before the Fukushima trag- edy raised new concerns.

With slow growth expected for nuclear power, fossil fuels in limited supply, an oil production peak looming, and climate change worsening, where will our growing human population turn for clean and sustainable energy? People increasingly are turning to renewable sources of energy (Chapter 16): energy sources that cannot be depleted by our use.

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Go to www.masteringenvironmentalscience.com for homework assignments, practice quizzes, Pearson eText, and more.

C A L C U L A T I N G E C O L O G I C A L F O O T P R I N T S

Scientists at the Global Footprint Network calculate the en- ergy component of our ecological footprint by estimating the amount of ecologically productive land and sea required to absorb the carbon released from fossil fuel combustion. This translates into nearly 5.6 ha of the average American’s 8.0-ha ecological footprint. Another way to think about our footprint, however, is to estimate how much land would be needed to grow biomass with an energy content equal to that of the fossil fuel we burn.

Assume that you are an average American who burns about 6.7 metric tons of oil-equivalent in fossil fuels each year,

and that average terrestrial net primary productivity (p. 32) can be expressed as 0.0037 metric tons/ha/year. Calculate how many hectares of land it would take to supply our fuel use by present-day photosynthetic production.

Hectares of land for fuel production

You 1,811 Your class Your state United States

power? Why might safety at nuclear power plants be bet- ter in the future? Why might it be worse?

4. THINK IT THROUGH You have been elected governor of the state of Florida as the federal government is debat- ing what waters to open to offshore drilling for oil and natural gas. Drilling in Florida waters would create jobs for Florida citizens as well as revenue for the state in the form of royalty payments from oil companies. However, there is always the risk of a catastrophic oil spill, with its ecological, social, and economic impacts. Would you support or oppose offshore drilling off the Florida coast- line? Why? What questions would you ask of scientists before making your decision? What factors would you consider in making your decision?

5. THINK IT THROUGH You are the head of the national department of energy in a country that has just experi- enced a minor accident at one of its nuclear plants. A par- tial meltdown released radiation, but the radiation was fully contained inside the containment building, and there were no health impacts on area residents. However, citi- zens are terrified, and the media is stressing the dangers of nuclear power. Your country relies on its five nuclear plants for 25% of its energy and 50% of its electricity needs. It has no fossil fuel deposits and recently began a promis- ing but still-young program to develop renewable energy options. What will you tell the public at your next press conference, and what policy steps will you recommend taking to ensure a safe and reliable national energy supply?

1. Compare the energy component of your ecological foot- print calculated in this way with the 5.6 ha calculated using the method of the Global Footprint Network. Ex- plain why results from the two methods may differ.

2. Earth’s total land area is approximately 15 billion hec- tares. Compare this to the hectares of land for fuel pro- duction from the table.

3. In the absence of stored energy from fossil fuels, how large a human population could Earth support at the level of consumption of the average American, if all of Earth’s area were devoted to fuel production? Do you consider this realistic? Provide two reasons why or why not.

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16 Renewable Energy Alternatives Upon completing this chapter, you will be able to:

� Discuss the reasons for seeking alternatives to fossil fuels � Outline the major sources of renewable energy and assess their potential for growth � Describe the major sources, scale, and impacts of bioenergy � Describe the scale, methods, and impacts of hydroelectric power � Describe solar energy and the ways it is harnessed, and evaluate its advantages and disadvantages � Describe wind power and how we harness it, and evaluate its benefits and drawbacks � Describe geothermal energy and the ways we make use of it, and assess its advantages and disadvantages � Describe ocean energy sources and how we could harness them � Explain hydrogen fuel cells and weigh options for energy storage and transportation

Homes in the Vauban neighborhood of Freiburg, Germany, which produce more solar power than they use, and sell it to the grid

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CENTRAL CASE STUDY

Germany Goes Solar “Someday we will harness the rise and fall of the tides and imprison the rays of the sun.”

—Thomas A. Edison, 

“[Renewable energy] will provide millions of new jobs. It will halt global warming. It will create a more fair and just world. It will clean our environment and make our lives healthier.”

—Hermann Scheer, energy expert and German parliament member, 

W hen we think of solar energy, most of us envision a warm sunny place like Arizona

or southern California. Yet the country that produces the most solar power is

Germany, a European nation as far north as Canada with a climate like Maine’s.

Germany is the world’s top user of photovoltaic (PV) solar technology, which produces elec-

tricity from sunshine. In recent years Germany has installed half the world’s total of this tech-

nology. Germany now obtains more of its energy from solar power than any other nation, and

the amount grows each year.

How is this happening in such a cool and cloudy country? A bold federal policy is offering economic incentives to businesses and homeowners to promote so- lar power and other forms of renewable energy. Germany has a feed-in tariff system whereby utilities are man- dated to buy power from anyone who can generate power from renewable en- ergy sources and feed it into the electric grid. Under this system, utilities must pay guaranteed premium prices for this power under long-term contract. As a result, German homeowners and businesses have rushed to install more and more PV panels each year, and are selling their extra solar power to the utilities at a profit.

The feed-in tariffs apply to all forms of renewable energy. As a result, Germany ranks third in the world in electric power capacity from renewable sources, trailing only China and the United States, which have far more people and businesses. Germany aims to obtain 30% of its electricity and 14% of its heating energy from renewable sources by 2020. To make this happen, the German government has been allotting more public money to renewable energy than any

other nation—over $25 bil- lion annually in recent years.

Boosted by domestic demand, German industries have become global leaders in “green tech,” designing and selling renewable energy technologies around the world. Germany is second in PV production behind China, leads the world in production of biodiesel, and has recently developed several cellulosic ethanol facilities. Renewable energy industries in Germany

today employ over 300,000 citizens. Germany’s push for renewable energy dates back

to 1990. The government had decided to phase out its nuclear power plants because of safety concerns, yet by shutting these down, the nation would lose virtually all its clean energy. With few domestic fossil fuel supplies, Germans would find their economy ut- terly dependent on oil, gas, and coal imported from Russia and the Middle East.

Enter Hermann Scheer, a member of the German parliament and an expert on renewable energy. While everyone else assumed that technologies for harness- ing solar, wind, and geothermal energy were costly, risky, and not ready for prime time, Scheer saw them

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as a great economic opportunity—and as the only long- term answer. In 1990, Scheer helped push through a landmark law establishing feed-in tariffs. Ten years later, the law was revised and strengthened: The Renewable Energy Sources Act of 2000 aimed to promote renewa- ble energy production and use, enhance the security of the energy supply, reduce carbon emissions, and lessen the many external costs (p. 92) of fossil fuel use.

Under the law, each renewable source is as- signed its own payment rate according to market considerations, and most rates are reduced year by year in order to encourage increasingly efficient means of producing power. In 2004 and in 2009, the govern- ment adjusted the amounts utilities were required to pay homeowners and businesses for their energy production. Then in 2010, the German government slashed PV solar tariff rates by 16% in order to reduce the cost of the subsidies to taxpayers and because PV market prices had already fallen by half. In response, sales of PV modules skyrocketed as Germans rushed to lock in the old rates. In 2010 alone, Germans installed 7 gigawatts of PV solar capacity—over 2.5 times the total cumulative capacity of the United States.

By replacing some of its fossil fuel use with renew- able energy, Germany has reduced its emissions of carbon dioxide by 140 million tons per year—equal to taking 24 million cars off the road. Half of this total is due to energy paid for under the feed-in tariff system. Since 1990, carbon dioxide emissions from German energy sources have fallen by over 20%, and emissions of seven other major pollutants (CH4, N2O, SO2, NOX, CO, VOCs, and dust) have been reduced by 12–95%.

Germany’s success is serving as a model for other nations. As of 2011, more than 60 nations had imple- mented some sort of feed-in tariffs. Spain and Italy ignited their wind and solar development as a result. In North America, Vermont and Ontario established feed-in tariff systems similar to Germany’s, while California, Hawaii, Oregon, and Washington conduct more-limited programs. In 2010, Gainesville, Florida, became the first U.S. city to establish feed-in tariffs. Moreover, utilities in 46 U.S. states now offer net me- tering, in which utilities credit customers who produce renewable power and feed it into the grid. As more na- tions, states, and cities develop policies to encourage renewable energy, we may soon experience a historic transition in the way we meet our energy demands. �

RENEWABLE ENERGY SOURCES Germany’s bold federal policy is just one facet of a global shift toward renewable energy. Across the world, nations are searching for ways to move away from fossil fuels while

ensuring a reliable and affordable supply of energy for their economies.

Renewable sources are growing fast Today’s economies are powered largely by fossil fuels; 81% of our energy comes from oil, coal, and natural gas (FIGURE 16.1A). These three fuels also power two-thirds of the world’s electricity generation (FIGURE 16.1B). Fossil fuels helped to drive the industrial revolution, increase our material prosperity, and create the society we enjoy today. However, these nonrenewable energy sources will not last forever. Eas- ily extractable supplies of oil and natural gas will likely soon dwindle (Chapter 15). Moreover, our use of coal, oil, and natural gas imposes health and environmental impacts, social costs, and security risks (Chapters 14 and 15). For these rea- sons, most energy experts accept that the world’s economies

New renewables (0.7%)

Hydro (2.2%)

Nuclear (5.8%)

Coal (27.0%)

Coal (41.0%)

Natural gas (21.1%)

Natural gas (21.3%)

Nuclear (13.5%)

Hydro (15.9%)

Biomass (10.0%)

Oil (33.2%)

Oil (5.5%)

Biomass and new renewables (2.8%)

(a) World energy production, by source

(b) World electricity generation, by source

FIGURE 16.1  Fossil fuels account for 81% (a) of the world’s energy production. Nuclear power and hydroelectric power contribute substantially to global electricity generation (b), but fossil fuels still power two-thirds of our electricity. Data are for 2008, from International Energy Agency, 2010. Key world energy statistics 2010.

Paris: IEA.

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Geothermal (2.6%)

Wind (11.5%)

Solar (1.4%)

Hydropower (60.1%)

Biomass (53.4%)

Biomass (13.4%)

Hydropower (31.2%)

Wind (22.5%)

Solar (0.3%)

Geothermal (3.7%)

(a) U.S. consumption of renewable energy, by source

(b) U.S. electricity generation from renewable sources

FIGURE 16.2  Only 8% of the energy consumed in the United States each year comes from renewable sources. Of this amount (a), most derives from biomass energy and hydropower. Wind power, geothermal energy, and solar energy together account for just 15% of this amount. Similarly, just 10.2% of electricity generat- ed in the United States (b) comes from renewable energy sources, predominantly hydropower. Data are for 2010, from Energy Information Administration, U.S. Department of Energy.

will need to shift from fossil fuels to energy sources that are less easily depleted and are gentler on our environment and health.

Our scientists, engineers, and entrepreneurs have de- veloped a range of alternatives to fossil fuels. The main non- renewable alternative is nuclear energy (pp. 345–350). Re- newable alternatives include biomass, hydropower, solar, wind, geothermal, and ocean energy sources. Biomass and hy- dropower are well-established and widely used sources. The other renewable sources are often termed “new renewables” because they are not yet widely used and they are harnessed using technologies still in a rapid phase of development. These sources can provide energy for three types of applications: (1) power for electricity, (2) heating of air or water, and (3) fuel for vehicles.

As renewable energy sources replace fossil fuels, they help alleviate air pollution (Chapter 13) and the greenhouse gas emissions that drive global climate change (Chapter 14). Unlike fossil fuels, many renewable sources are inexhaustible on time scales relevant to our society. Developing renewables can also help diversify an economy’s energy mix, thus reduc- ing price volatility and dependence on foreign fuel imports (p. 342). Finally, the design, installation, and management re- quired to develop technologies and rebuild our society’s en- ergy infrastructure will be a major source of employment for young people today, through green-collar jobs. Over 3 mil- lion people work in renewable energy jobs around the world already, and the number is rising.

Nations and regions vary in the renewable sources they use. Developing nations account for most use of combustible renewables, or biomass, such as fuelwood. In the United States, most renewable energy comes from biomass and hydropower (FIGURE 16.2A). Of electricity generated in the United States from renewables, hydropower accounts for nearly two-thirds (FIGURE 16.2B).

Although they comprise a minuscule proportion of our energy budget, the “new renewable” energy sources are grow- ing quickly. Over the past four decades, solar, wind, and ge- othermal energy sources have grown far faster than has the overall energy supply. The leader in growth is wind power, which has expanded by nearly 50% each year since the 1970s. Because these sources started from such low levels of use, however, it will take them some time to catch up to conven- tional sources. The absolute amount of energy added by a 50% increase in wind power today equals the amount added by just a 1% increase in oil, coal, or natural gas!

Policy can accelerate our transition Rapid growth in renewable energy sectors seems likely to continue as population and consumption grow, global energy demand expands, fossil fuel supplies decline, and people de- mand cleaner environments. Yet we cannot switch complete- ly to renewable energy sources overnight, because there are technological and economic barriers. Currently, most renew- ables lack adequate technology and infrastructure to transfer power on the required scale.

Rapid technological advances in recent years, however, suggest that most remaining barriers are political. Renew-

able energy sources have received far less in subsidies and tax breaks from governments than have conventional sources. In the United States over the past three decades, renewable en- ergy sources have been granted just one-sixth the public fund- ing for research and development that nuclear energy and fossil fuels have received (FIGURE 16.3). Research and devel- opment of renewable sources have gone underfunded because fossil fuels continue to be available at inexpensive prices, even though these low prices are enabled in part by government policy that responds to lobbying from fossil fuel interests.

Public policy steps can accelerate our societal transition to renewable energy. Germany’s feed-in tariff policy provides

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a prime example of an economic policy tool (pp. 106–107) that can hasten the spread of renewable energy by creating financial incentives for businesses and individuals. Renew- able energy efforts also received support when many national governments responded to the global financial downturn of 2008–2009 by enacting stimulus packages and boosting spending on green energy programs to help create jobs. As more governments, utilities, corporations, and consumers turn to renewable energy, prices of renewables should con- tinue to fall, further hastening their adoption.

BIOENERGY Bioenergy—also known as biomass energy—is energy obtained from biomass. Biomass (p. 69) consists of organic material derived from living or recently living organisms, and it contains chemical energy that originated with sunlight and photosynthesis. We harness bioenergy from many types of plant matter, including wood from trees, charcoal from wood charred in the absence of oxygen, and matter from agricultural crops, as well as from combustible animal waste products such as cattle manure.

The great attraction of bioenergy is that—in principle— it is renewable and releases no net carbon dioxide into the atmosphere. Although burning biomass emits plenty of carbon dioxide, this is balanced by the fact that photosynthesis had pulled this amount of carbon dioxide from the atmos- phere to create the biomass just years, months, weeks, or days before. Therefore, in theory, when we replace fossil fuels with bioenergy, we reduce net carbon flux to the atmosphere, help- ing to alleviate global climate change (Chapter 14). However, in practice it is not so simple, and judging the sustainability of any given bioenergy strategy requires careful consideration of the type of biomass source we are using and the way we gain energy from it.

Bioenergy comes from diverse sources To a poor farmer in Africa, bioenergy entails cutting wood from trees or collecting livestock manure and burning it to heat and cook for her family. To an industrialized farmer in Iowa, bioenergy means shipping his grain to a high-tech re- finery that converts it to liquid fuel to run automobiles. The diversity of sources and approaches involved in bioenergy (TABLE 16.1) gives us many ways to address our energy challenges.

Over 1 billion people use wood from trees as their prin- cipal energy source. In developing nations, especially in ru- ral areas, families gather fuelwood to burn in their homes for heating, cooking, and lighting (FIGURE 16.4). Although fossil fuels are replacing traditional energy sources as developing nations industrialize, fuelwood, charcoal, and manure still account for 35% of energy use in these nations, and up to 90% in the poorest nations.

Fuelwood and other traditional biomass sources con- stitute nearly 80% of all renewable energy used worldwide. However, biomass is renewable only if it is not overharvested. Harvesting fuelwood at unsustainably rapid rates will lead to deforestation, soil erosion, and desertification (pp. 188, 140), which can damage landscapes, diminish biodiversity, and im- poverish human societies.

While much of the world still relies on fuelwood, charcoal, and manure, new bioenergy approaches are being developed using a variety of materials to provide innovative types of energy (see Table 16.1). Some of these materials are

Fossil fuels $20.0 billion

Efficiency $11.7 billion

All renewable energy $12.4 billion

Nuclear $47.9 billion

FIGURE 16.3  Most U.S. research and development funding for energy has gone toward nuclear power and fossil fuels. Between 1974 and 2005, only 13% went toward all renewable energy sources combined. Data from International Energy Agency.

TABLE 16.1 Major Bioenergy Sources Direct combustion for heating ▶ Wood cut from trees (fuelwood) ▶ Charcoal ▶ Manure from farm animals

Biofuels for powering vehicles ▶ Corn grown for ethanol ▶ Bagasse (sugarcane residue) grown for ethanol ▶ Soybeans, rapeseed, and other crops grown for biodiesel ▶ Used cooking oil for biodiesel ▶ Plant matter treated with enzymes to produce cellulosic

ethanol ▶ Algae grown for biofuels

Biopower for generating electricity ▶ Crop residues (such as cornstalks) burned at power plants ▶ Forestry residues (such as wood waste from logging)

burned at power plants ▶ Processing wastes (such as waste from sawmills, pulp

mills, and paper mills) burned at power plants ▶ “Landfill gas” burned at power plants ▶ Livestock waste from feedlots for gas from anaerobic

digesters ▶ Organic components of municipal solid waste from

landfills

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burned in power plants to produce biopower, generating heat or electricity. Other sources can be converted into biofuels, liquid fuels used primarily to power automobiles.

Biopower generates electricity from biomass We harness biopower by combusting biomass to generate electricity. This can be done using a variety of sources and techniques.

Waste products The waste products of various indus- tries and processes may be used for biopower. These include woody debris from logging, liquid waste from pulp mills, or- ganic waste from landfills or feedlots, and residue from crops (such as cornstalks and corn husks).

Bioenergy crops We are beginning to grow certain types of plants as crops to generate biopower. These include fast- growing grasses such as bamboo, fescue, and switchgrass, as well as trees such as specially bred willows and poplars (FIG- URE 16.5). Many of these plants are also being grown to pro- duce liquid biofuels.

Combustion strategies At small scales, farmers, ranch- ers, or villages can operate modular biopower systems that use livestock manure to generate electricity. Small household biodigesters provide portable and decentralized energy pro- duction for remote rural areas.

At large scales, power plants built to combust bio- mass operate like those fired by fossil fuels (see Figure 15.4, p. 330); combustion heats water, creating steam to turn tur- bines and generators, thereby generating electricity. Much of the biopower produced so far comes from power plants that use cogeneration (p. 344) to generate both electricity and heating. These plants are often located where they can take advantage of forestry waste.

In some coal-fired power plants, wood chips, wood pel- lets, or other biomass is combined with coal in a specialized boiler in a process called co-firing. We can substitute biomass for up to 15% of the coal with only minor equipment modifi- cation and no appreciable loss of efficiency. Co-firing is a rela- tively easy way for utilities to expand their use of renewable energy.

We also harness biopower through gasification, in which biomass is vaporized at high temperatures in the absence of oxygen, creating a mixture of hydrogen, carbon monoxide, carbon dioxide, methane, and other gases. This mixture can generate electricity when used to turn a gas turbine to propel a generator in a power plant. We can also treat gas from gasi- fication in various ways to produce methanol (wood alcohol), synthesize a type of diesel fuel, or isolate hydrogen for use in hydrogen fuel cells (p. 375). An alternative method of heating biomass in the absence of oxygen results in pyrolysis, which produces a mix of solids, gases, and liquids. This includes a liquid fuel called pyrolysis oil, which can be burned to generate electricity.

Benefits and drawbacks By enhancing energy efficien- cy and recycling waste products, biopower helps move our utilities and industries in a sustainable direction. Biopower also helps mitigate climate change by reducing carbon diox- ide emissions, and capturing landfill gas reduces emissions of methane, a potent greenhouse gas. When biomass replaces coal in co-firing and direct combustion, biopower reduces emissions of sulfur dioxide because plant matter, unlike coal, contains no appreciable sulfur.

A disadvantage of biopower is that when we burn crops or plant matter for power, we deprive the soil of nutrients it would have gained from the plant matter’s decomposition. We essentially draw fertility from the soil and never return it, so that the soil becomes progressively depleted.

Biofuels can power automobiles Liquid fuels from biomass sources are powering millions of vehicles on today’s roads. The two primary biofuels developed so far are ethanol (for gasoline engines) and biodiesel (for die- sel engines).

FIGURE 16.4  Well over a billion people in developing countries rely on fuelwood for heating and cooking. Wood cut from trees remains the major source of biomass energy used in the world today. In theory, biomass is renewable, but in practice it may not be if forests are overharvested.

FIGURE 16.5  Switchgrass, a fast-growing plant native to the North American prairies, provides fuel for biopower now and is being studied as a crop to provide cellulosic ethanol (p. 361).

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More growth is assured, because the Energy Independence and Security Act passed by Congress in 2007 mandates pro- duction and use of 136 billion L (36 billion gal) per year of ethanol by 2022.

Any vehicle with a gasoline engine runs well on gaso- line blended with up to 10% ethanol, but automakers are also producing flexible-fuel vehicles that run on E-85, a mix of 85% ethanol and 15% gasoline. Over 9 million such cars are on U.S. roads today. In Brazil, half of all new cars are flexible-fuel vehicles, and ethanol from crushed sugarcane residue (called bagasse ) accounts for 40% of all fuel that Brazil’s drivers use.

The enthusiasm for corn-based ethanol shown by U.S policymakers is not widely shared by environmental scien- tists. Growing corn to produce ethanol exerts considerable impacts on ecosystems, including pesticide use, fertilizer use, fresh water depletion, and other consequences of mono- cultural industrial agriculture (pp. 136–137 ). Corn ethanol crops take up precious land (see ENVISIONIT, p. 360 ). If we were to try to produce all the automotive fuel now used in the United States with ethanol from corn, the nation would need to expand its already immense corn acreage by more than 60%, with no loss of productivity and without producing any corn for food. Even at our current level of production, ethanol already competes with food production and drives up food prices.

Growing corn for ethanol also requires substantial inputs of fossil fuel energy (for running farm equipment, making petroleum-based pesticides and fertilizers, transporting corn to processing plants, and heating water in refineries to distill ethanol). In fact, corn ethanol yields only a modest amount of energy relative to the energy that needs to be input. The EROI ( energy returned on investment ) ratio (p. 328 ) for corn-based ethanol is variable, but recent estimates place it around 1.5:1.

Ethanol Ethanol is the alcohol in beer, wine, and liquor. It is produced as a biofuel by fermenting biomass, generally from carbohydrate-rich crops, in a process similar to brewing beer. In fermentation, carbohydrates are converted to sug- ars and then to ethanol. Spurred by the 1990 Clean Air Act amendments and generous government subsidies, ethanol is widely added to gasoline in the United States to reduce auto- motive emissions. In 2010 in the United States, over 49 billion L (13 billion gal) of ethanol were produced, mostly from corn ( FIGURE 16.6 ). This amount is growing rapidly, and nearly 200 U.S. ethanol production facilities are now operating.

B ill

io n

g al

lo n

0 1980 1985 1990 1995

World

Year

United States

2000 2005 2010

(b) Ethanol production, 1980–2010

(a) Corn grown for ethanol

FIGURE 16.6  About 30% of the U.S. corn crop (a) is used to produce ethanol, a biofuel that is widely added to gasoline in the United States. Brazil produces most of the rest of the world’s ethanol, from bagasse (sugarcane residue). Ethanol production (b) has grown rapidly in the last several years. Data from Renewable Fuels Association.

FAQ

Q: If we substitute ethanol for gasoline, won’t that solve most of our problems with oil dependency?

A: In the United States, government subsidies for corn-based ethanol have been politically popular, and many people believe that the more ethanol we produce and substitute for gasoline, the better off we’ll be. Increasing the proportion of ethanol in gasoline does indeed help to conserve oil and reduce reliance on foreign imports. However, obtaining the amount of corn ethanol needed to replace gasoline entirely would require that impractically large amounts of land be converted to corn production. Moreover, so much corn would likely be diverted from food to fuel that food prices would rise sharply. This is why researchers are studying other plants as more-efficient sources of ethanol, and trying to develop ways of producing cellulosic ethanol from crop and forestry wastes.

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E n

v isio

n it

➤

Ethanol at the pump

Area of corn grown in the U.S. today

Ethanol re�nery

Area of corn that would need to be grown if ethanol were to replace all gasoline in U.S.

In the quest for carbon-neutral alternatives to gasoline, what biofuel could be better, many people have thought, than ethanol made from America’s #1 crop, corn?

But growing corn for ethanol requires nearly as much energy as it produces ... and it demands that we convert immense areas of land to industrial farming.

And when fuel crops compete with food crops, that drives food prices up.

So, scientists are racing to find more efficient and sustainable biofuels.

You Can Make a Difference Ask your legislators to support university research on non-food-crop biofuels like switchgrass, algae, and cellulosic ethanol.

Urge policymakers to create financial incentives for sustainable biofuels.

Reduce your gasoline consumption by driving less and driving a more fuel-efficient vehicle. You’ll save money, too!

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Biofuels Do you think producing and using ethanol from corn is a good idea? Do the benefits outweigh the drawbacks? Should we invest bil- lions of dollars into developing next-generation biofuels such as algae and cellulosic ethanol? Can

you suggest ways of using biofuels that would minimize environmental impacts?

FIGURE 16.7  At Loyola University Chicago, students and staff produce biodiesel from waste vegetable oil from the dining halls and use it to fuel this biodiesel van. A grant from the U.S. Environmental Protection Agency (EPA) funds them to transport this mini-biodiesel reactor to local high schools to teach students about alternative fuels.

This means that to gain 1.5 units of energy from ethanol, we need to expend 1 unit of energy.

Biodiesel Drivers of diesel-fueled vehicles can use biodie- sel, a fuel produced from vegetable oil, used cooking grease, or animal fat. The oil or fat is mixed with small amounts of ethanol or methanol in the presence of a chemical catalyst. In Europe, where most biodiesel is used, rapeseed oil is the oil of choice, whereas U.S. biodiesel producers generally use soybean oil. Vehicles with diesel engines can run on 100% biodiesel, or biodiesel can be mixed with conventional petro- diesel; a 20% biodiesel mix (called B20) is common.

Biodiesel cuts down on emissions compared with petro- diesel. Its fuel economy is almost as good, it costs just slight- ly more, and it is nontoxic and biodegradable. Increasing numbers of people are fueling their cars with biodiesel from waste oils (FIGURE 16.7). Some buses and recycling trucks now run on biodiesel, and many state and federal fleets use biodiesel blends.

Using waste oil as a biofuel is sustainable, but most bi- odiesel today, like most ethanol, comes from crops grown spe- cifically for the purpose—and these crops have environmental impacts. Growing soybeans in Brazil (p. 189) or oil palms in Southeast Asia (p. 191) hastens the loss of tropical rainforest. Growing soybeans in the United States and rapeseed in Eu- rope takes up large areas of land as well.

Novel biofuels Because the major crops grown for bio- diesel and for ethanol exert heavy impacts on the land, farmers and agricultural scientists are experimenting with a variety of other crops, from wheat, sorghum, cassava, and sugar beets to less-known plants such as hemp, jatropha, and the grass miscanthus. One promising next-generation biofuel crop is algae. Several species of these photosyn- thetic microorganisms produce large quantities of lipids that can be converted to biodiesel. Alternatively, carbohy- drates in algae can be fermented to create ethanol. In fact, a variety of fuels, including jet fuel, can be produced from

algae. Algae grow much faster than terrestrial crops, can be harvested every few days, and produce much more oil than other biofuel crops.

Because relying on any monocultural crop for energy may not be a sustainable strategy, researchers are refining techniques to produce cellulosic ethanol by using enzymes to produce ethanol from cellulose, which gives structure to all plant material. This would be a substantial advance because ethanol as currently made from corn or sugarcane uses starch, which is valuable to us as food. Cellulose, in contrast, is of no food value to people yet is abundant in all plants. If we can produce cellulosic ethanol in commercially feasible ways, then ethanol could be made from low-value crop waste (such as cornstalks and corn husks), rather than from high-value crops.

Is bioenergy carbon-neutral? In principle, energy from biomass is carbon-neutral, re- leasing no net carbon into the atmosphere. This is because burning biomass releases carbon dioxide that plants had re- cently pulled from the atmosphere during photosynthesis. However, burning biomass for energy is not carbon-neutral if forests are destroyed in order to plant bioenergy crops. Forests sequester more carbon (in vegetation and in soil) than do croplands, so cutting forests to plant crops will in- crease carbon f lux to the atmosphere. Bioenergy also fails to be carbon-neutral if we need to use fossil-fuel energy to pro- duce the biomass (for instance, by driving tractors, using fertilizers, and applying pesticides to grow biofuel crops).

International climate change policy so far has failed to en- courage sustainable bioenergy approaches. The Kyoto Proto- col (p. 319) required nations to submit data on emissions both from energy use and from land use change (such as deforesta- tion), but only the emissions from energy use were “counted” toward judging nations’ performance under the treaty. Nego- tiators trying to design a follow-up treaty to Kyoto have been trying to address this (p. 319). In the meantime, researchers are busy trying to develop means of using bioenergy that are truly renewable and carbon-neutral. With continued research and careful decision-making, our many bioenergy options may provide promising avenues for sustainable replacement of fossil fuels.

HYDROELECTRIC POWER Next to biomass, we draw more renewable energy from the mo- tion of water than from any other resource. In hydroelectric power, or hydropower, we use the kinetic energy of moving water to turn turbines and generate electricity.

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Modern hydropower uses three approaches Most of our hydroelectric power today comes from im- pounding water in reservoirs behind concrete dams that block the f low of river water, and then letting that water pass through the dam. Because immense amounts of wa- ter are stored behind dams, this is called the storage tech- nique. As reservoir water passes through a dam, it turns the blades of turbines, which cause a generator to gener- ate electricity (FIGURE 16.8). Electricity generated in the

powerhouse of a dam is transmitted to the electric grid by transmission lines, while the water f lows into the riverbed below the dam and continues downriver. By storing water in reservoirs, dam operators can ensure a steady and pre- dictable supply of electricity, even during periods of natu- rally low river f low.

An alternative approach is the run-of-river technique, which generates electricity without greatly disrupting the flow of river water. Several methods can be used; one is to divert a portion of a river’s flow through a pipe or channel, passing it through a powerhouse and returning it to the river. Run-of-river

(a) Ice Harbor Dam, Snake River, Washington (b) Turbine generator inside McNary Dam, Columbia River

Outflow

Stator

Rotor

Turbine

Generator

Dam

Reservoir

Powerlines

Intake Powerhouse

Water flows from the reservoir through the dam.

The flowing water turns the turbine.

The turbine turns the rotor, which consists of a series of magnets.

Electricity is produced as the rotor spins past the stator, which is the stationary part of the generator made of coils of copper wire.

FIGURE 16.8  Large dams, such as the Ice Harbor Dam on the Snake River in Washington (a), generate sub- stantial amounts of hydroelectric power. Inside these dams, flowing water is used to turn turbines (b) and gener- ate electricity. Water is funneled from the reservoir through a portion of the dam (c) to rotate turbines, which turn rotors containing magnets. The spinning rotors generate electricity as their magnets pass coils of copper wire. Electrical current is transmitted away through power lines, and the river’s water flows out through the base of the dam.

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wealth. Canada, Brazil, Norway, Austria, Switzerland, Ven- ezuela, and other nations today obtain large amounts of their energy from hydropower (TABLE 16.2).

Today the world is witnessing some gargantuan hydro- electric projects. China’s recently completed Three Gorges Dam (pp. 261, 263) is the world’s largest. However, hydro- power is not likely to expand much more. One reason is that most of the world’s large rivers are already dammed. Anoth- er reason is that people have grown more aware of the eco- logical impacts of dams, and in some regions residents are resisting dam construction. In the United States, 98% of riv- ers appropriate for dam construction already are dammed, many of the remaining 2% are protected under the Wild and Scenic Rivers Act, and some people now want to dismantle certain dams and restore river habitats (p. 261). The Inter- national Energy Agency forecasts that hydropower’s share of electricity generation will decline between now and 2030, whereas the share of other renewable energy sources will tri- ple, from 2% to 6%.

SOLAR ENERGY The sun releases astounding amounts of energy by convert- ing hydrogen to helium through nuclear fusion. The tiny pro- portion of this energy that reaches Earth is enough to drive most of the processes in the biosphere, helping to make life possible on our planet. Each day in total, Earth receives enough solar energy, or energy from the sun, to power human consumption for a quarter of a century. On average, each square meter of Earth’s surface receives about 1 kilowatt of solar energy—17 times the energy of a lightbulb. As a result, a typical home has enough roof area to meet all its power needs with rooftop panels that harness solar energy. However, we are still in the process of developing solar technologies and learn- ing the most effective and cost-efficient ways to put the sun’s energy to use.

systems are useful in areas remote from electrical grids and in regions without the economic resources to build and maintain large dams. This approach cannot guarantee reliable water flow in all seasons, but it minimizes many of the impacts of the stor- age technique.

To better control the timing of flow, pumped-storage hy- dropower can be used. In the pumped-storage approach, water is pumped from a lower reservoir to a higher reservoir during times when demand for power is weak and prices are low; when demand is strong and prices are high, water is allowed to flow downhill through a turbine, generating electricity. Although energy must be input to pump the water, pumped storage can be profitable, and it also can help even out power supply when paired with intermittent sources such as solar and wind power.

Hydropower is clean and renewable, but also has impacts Hydropower has two clear advantages over fossil-fuel-gener- ated electricity. First, it is renewable; as long as precipitation falls from the sky and fills rivers and reservoirs, we can use water to turn turbines. Second, no carbon compounds are burned in the production of hydropower, so no carbon diox- ide or other pollutants are emitted into the atmosphere. Of course, fossil fuels are used in constructing and maintaining dams—and recent evidence indicates that large reservoirs re- lease the greenhouse gas methane as a result of anaerobic de- cay in deep water. But overall, hydropower accounts for only a small fraction of the greenhouse gas emissions typical of fossil fuel combustion.

In addition, hydropower is efficient. It is thought to have an EROI ratio of 10:1 or more—at least as high as any other modern-day energy source.

Although it is renewable, efficient, and produces lit- tle air pollution, hydropower does exert negative impacts. Damming rivers (pp. 261–263) destroys habitat for wildlife as riparian areas above dam sites are submerged and those below dam sites often are starved of water. Because water discharge is regulated to optimize electricity generation, the natural flooding cycles of rivers are disrupted. Suppressing flooding prevents river floodplains from receiving fresh, nu- trient-laden sediments. Instead, sediments become trapped behind dams, where they begin filling the reservoir. Dams also cause thermal pollution (p. 269) by changing water tem- peratures, and this, along with habitat alteration, has dimin- ished or eliminated many native fish populations in dammed waterways. In addition, dams generally block the passage of fish and other aquatic creatures, fragmenting the river and re- ducing biodiversity in each stretch. These ecological impacts generally translate into negative social and economic impacts on local communities.

Hydroelectric power is widely used, but may not expand much more Hydropower accounts for 16% of the world’s electricity pro- duction (see Figure 16.1b). For nations with large amounts of river water and the economic resources to build dams, hydro- electric power has been a keystone of their development and

TABLE 16.2 Top Producers of Hydropower Nation

Hydropower produced (terawatt-hours)

Percentage of electricity generation from hydropower

China 585 16.9

Canada 383 58.7

Brazil 370 79.8

United States 282 6.5

Russia 167 16.0

Norway 141 98.5

India 114 13.8

Venezuela 87 72.8

Japan 83 7.7

Sweden 69 46.1

Rest of world 1,007 13.6 Data is for 2008, from the International Energy Agency.

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We can collect solar energy using passive or active methods The simplest way to harness solar energy is through pas- sive solar energy collection. In this approach, buildings are designed and building materials are chosen to maximize absorption of sunlight in winter and to keep the interior cool in the heat of summer. One such technique involves installing low, south-facing windows to maximize the capture of sunlight in winter. Overhangs shade these windows in sum- mer, when the sun is high in the sky and when cooling, not heating, is desired. Passive solar techniques also may use construction materials that absorb heat, store it, and release it later. Such thermal mass (of straw, brick, concrete, or other materials) often makes up f loors, roofs, and walls, or can be used in portable blocks. Planting vegetation around a build- ing to buffer the structure from temperature swings is an- other passive solar approach.

In contrast, active solar energy collection makes use of devices to focus, move, or store solar energy. We can use various active solar technologies to heat water and air in our homes and businesses. One common method involves installing flat-plate solar collectors on rooftops. These panels generally consist of dark-colored, heat-absorbing metal plates mounted in flat glass-covered boxes. Water, air, or antifreeze runs through tubes that pass through the collectors, transfer- ring heat to the building or its water tank (FIGURE 16.9). Heat- ed water can be stored for later use and passed through pipes designed to release the heat into the building.

Over 1.5 million U.S. homes and businesses heat water with solar collectors, although most of this is water for swim- ming pools. Active solar heating is used more widely in China and also in Europe, where Germans motivated by feed-in tar- iffs installed 200,000 new systems in 2008 alone.

Concentrating solar rays magnifies energy We can magnify the intensity of solar energy by gathering sunlight from a wide area and focusing it on a single point. This is the principle behind solar cookers, simple portable ov- ens that use ref lectors to focus sunlight onto food and cook it. Such cookers are proving useful in the developing world.

At much larger scales, utilities are using this principle to generate electricity. Concentrated solar power (CSP) is being harnessed by several methods in the California desert and else- where. In one approach, numerous mirrors concentrate sun- light onto a receiver atop a tall “power tower” (FIGURE 16.10). From this central receiver, heat is transported by air or fluids (often molten salts) and piped to a steam-driven generator to create electricity. CSP facilities can harness light from lenses or mirrors spread across large areas of land, and the lenses or mirrors may swivel to track the sun’s movement across the sky.

The International Energy Agency estimates that just 260 km2 (100 mi2) of Nevada desert could generate enough elec- tricity using CSP to power the entire U.S. economy. Currently, German industrialists and investors are spearheading an effort to create an immense CSP facility in Africa’s Sahara Desert. In

FIGURE 16.9  Solar systems for heating water vary in their designs, but typically � sunlight is gathered on a flat-plate solar collector, until a controller � switches on a pump � to circulate fluid through pipes to the collector. The sunlit collec- tor heats the fluid �, which flows through pipes � to a water tank. The hot fluid in the pipes transfers heat to the water in the tank, and this heated water is available for the taps of the home or business. Gen- erally, an external boiler � kicks in to heat water when solar energy is not available.

Boiler

Cold water supply

Hot water to tap

Water tank

Pump

Controller

Flat plate solar collector

Sunlight shines on flat plate solar collector

Controller senses when collector is warm enough

Pump switches on, circulating fluid through system

Flat plate solar collector, warmed by sun, heats fluid in pipe

Heated fluid flows to water tank, where pipes transfer heat to water in tank

Boiler heats water as needed when solar energy is not available

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FIGURE 16.10  The Solar Two facility in the southern California desert harnesses concentrated solar power. Hundreds of mirrors reflect sunlight onto a receiver atop a “power tower.” The result- ing heat is transported through fluid-filled pipes to a steam-driven generator that produces electricity for 10,000 households.

p-type layer (boron-enriched)

Electron flow

Junction

n-type layer (phosphorus- enriched)

Electricity generated

Photovoltaic cell

Module

–

Panel

Sunlight

Array

FIGURE 16.11  A photovoltaic (PV) cell converts sunlight to electrical energy. When sunlight hits the silicon layers of the cell, electrons are knocked loose from some of the silicon atoms and tend to move from the boron- enriched “p-type” layer toward the phosphorus-enriched “n-type” layer. Connecting the two layers with wiring remedies this imbalance as electrical current flows from the n-type layer back to the p-type layer. This direct cur- rent (DC) is converted to alternating current (AC) to produce usable electricity. PV cells are grouped in modules, which comprise panels, which can be erected in arrays.

tal impacts that such large-scale developments may pose (see THE SCIENCE BEHIND THE STORY, pp. 366–367).

Photovoltaic cells generate electricity directly The most direct way to produce electricity from sunlight involves photovoltaic (PV) systems. Photovoltaic (PV) cells convert sunlight to electrical energy when light reaches the PV cell and strikes one of a pair of plates made primarily of silicon, a semiconductor that conducts electricity. The light causes one plate to release electrons, which are attracted by electrostatic forces to the opposing plate. Connecting the two plates with wires enables the electrons to f low back to the original plate, creating an electrical current (direct current, DC), which can be converted into alternating current (AC) and used for residential and commercial electrical power (FIGURE 16.11). Small PV cells may already power your watch or your calculator. Atop the roofs of buildings, PV cells are arranged in modules, comprising panels, which can be gath- ered together in arrays. Arrays of PV panels can be seen on the roofs of the German houses in the photo that opens this chapter (p. 353).

Researchers are experimenting with variations on PV technology, and manufacturers today are already developing

this planned $775 billion project, called Desertec, thousands of mirrors spread across vast areas of desert in Morocco would harness the Sahara’s abundant sunlight and transmit electric- ity to Europe, the Middle East, and North Africa. However, many people are increasingly anxious about the environmen-

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This has become clear in recent years as the Cape Wind project in Massachusetts and a number of large solar projects in California have brought a host of issues that some proponents of clean energy had not

considered. Scientific study of these impacts is just getting underway and will be important as energy develop- ment proceeds.

Several dozen solar power instal- lations are currently under review for

the Mojave Desert and other arid regions of California, and these would, if constructed, cover many thousands of acres of land (see photo). Desert environments are particularly sensitive, so researchers say we should expect substantial impacts. Besides altering the pristine appearance of an undevel- oped landscape, arrays of thousands of mirrors or panels affect communities of plants and animals by casting shade and altering microclimate. Altered conditions tend to hurt native desert- adapted species while helping invasive weeds. At existing solar facilities, the sites are graded (damaging fragile soils) and sprayed with herbicide. Human presence increases as work- ers maintain the facilities. Solar power plants also require water for cooling and cleaning, and water is scarce in the arid regions hosting most of these facilities. All these impacts will have consequences for plants, animals, and ecosystems.

Large-scale projects need govern- ment approval and are subject to the environmental impact statement proc- ess (p. 100). As a result, teams of re- searchers study the conditions at each site to determine what impacts energy development may have. If impacts are judged to be severe enough, then government agencies can insist that plans be amended. For instance, the California Energy Commission asked for limits on the proposed Calico Solar

thin-film solar cells, photovoltaic materials compressed into ultra-thin sheets. Although less efficient at converting sun- light to electricity, they are cheaper to produce. Thin-film technologies can be incorporated into roofing shingles and potentially many other types of surfaces, even highways! For these reasons, many people view thin-film solar technologies as a promising direction for the future.

Photovoltaic cells of all types can be connected to batter- ies that store the accumulated charge until needed. Or, pro-

ducers of PV electricity can sell power to their local utility if they are connected to the regional electric grid. In parts of 46 U.S. states, homeowners can sell power to their utility in the process called net metering, in which the value of the power the consumer provides is subtracted from the con- sumer’s monthly utility bill. Feed-in tariff systems like Ger- many’s go a step further by paying producers more than the market price of the power, offering producers the hope of turning a profit.

T H E S C I E N CE B E H I N D T H E S TO RY

What Are the Impacts of Solar and Wind Development?

This solar plant in Kramer Junction, California, is one of a complex of nine that spread across more than 650 ha (1,600 acres) of the Mojave Desert, providing power for over 230,000 homes. Large-scale solar power farms require vast areas of land and exert substantial environmental impacts, yet researchers estimate that this land use is not appreciably greater than that demanded by fossil fuels. Using coal for energy takes up at least as much land, once one includes the strip mining needed to obtain the coal.

Local residents demonstrate for and against the proposed Cape Wind farm.

Renewable energy sources alleviate many of the negative environmen-tal and social impacts of fossil fuel combustion, and they may one day sustainably fulfill our energy needs. However, this does not mean that renewable energy is a panacea free of costs. As our society decides how to pursue energy sources such as solar power and wind power, we will need to consider their impacts as well as their benefits.

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is just 2%. However, solar energy use has grown by over 30% annually worldwide in the past four decades, a growth rate second only to that of wind power. Solar energy is proving especially attractive in developing countries, many of which are rich in sun but poor in power infrastructure, and where hundreds of millions of people still live without electricity.

PV technology is the fastest-growing power generation technology today, having recently doubled every two years

Project in southern California in 2010, after biologists concluded that the project would damage habitat of the desert tortoise and bighorn sheep. The company agreed to reduce the size of its footprint by nearly half, reducing estimated impacts to wildlife by 80%, and the Commission approved the project.

In central California, a solar project underwent 18 months of envi- ronmental analysis and was approved only after the Solargen company agreed to purchase and set aside 23,000 acres of preserved land as “mitigation” for the 3,200 acres it was developing. A third California solar project, the Topaz Solar Farm, was scaled back in size after researchers found that scaling back was needed to protect farmland; minimize aesthetic impacts; and lessen disturbance to tule elk, kit foxes, pronghorn antelope, burrowing owls, and seasonal freshwa- ter pools.

On the U.S. Great Plains, researchers from the National Renewable Energy Laboratory are currently studying impacts of solar installations on prairie ecosystems, by comparing a developed site and an undeveloped control site.

Given the impacts of large-scale solar facilities, researchers have de- termined that installing photovoltaic panels on rooftops of buildings is a low-impact alternative. Simply adding PV panels or roofing tiles to a rooftop has no effect on the landscape. One study, led by five Dutch, German, and American researchers, com- pared impacts of various ground- based and rooftop PV systems in Ger- many and in Arizona. The researchers assessed impacts over the systems’ entire life cycles (from production to installation through operation). They

found that besides avoiding land use impacts, the rooftop systems also emitted significantly fewer green- house gases.

A different study in 2008 meas- ured the amount of energy required by PV cells throughout their life cycles and found that replacing fossil fuel energy with PV solar power would prevent 89–98% of greenhouse gas emissions.

The overall messages from stud- ies so far are that (1) solar power, even with its impacts, is still cleaner and more sustainable than fossil fuel power; and (2) we can minimize the impacts of solar power by using rooftop panels and developing better technologies.

Similar messages are emerg- ing from the scientific study of wind power. One major concern is that birds and bats are killed when they fly into the spinning blades of turbines. At California’s Altamont Pass wind farm, turbines killed dozens of golden eagles and other raptors in the 1990s. Studies since then at other sites sug- gest that bird deaths may be a less se- vere problem than was initially feared, but uncertainty remains.

For instance, one European study indicated that migrating seabirds fly past offshore turbines without prob- lem, but other data show that resident seabird densities have declined near turbines. On land, the wind industry es- timates that about two birds are killed per 1-megawatt-turbine per year. This is far fewer than the hundreds of mil- lions of birds being killed each year by television, radio, and cell phone tow- ers; pesticides; automobiles; glass win- dows; and domestic cats (see graph). If you own a cat and let it outside, you may be killing more wildlife than are most wind farms.

At this point, bat mortality appears to be a more severe problem at wind turbines. One key for protecting bats and birds may be selecting sites that are not on migratory flyways or in the midst of prime habitat for species that are likely to fly into the blades. Further research on these questions is urgently needed.

Continued studies on the impacts of wind and solar development should help us find ways to harness renew- able energy and attain a sustainable energy future while minimizing the environmental and social impacts of this development.

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Wind turbines kill 88,000 - 320,000 birds per year in U.S.

Wind turbines kill birds that fly into them. Yet far more birds are killed by other human causes. Shown are ranges of recent estimates of yearly bird mortality in the United States from several main causes. Habitat alteration is responsible for still more than any of the causes shown. Data from American Bird Conservancy.

Solar energy is growing fast Active solar technology dates from the 18th century, but it was pushed to the sidelines as fossil fuels came to domi- nate our energy economy. Largely because of a lack of in- vestment, solar energy contributes just 0.15%—15 parts in 10,000—of the U.S. energy supply, and just 0.03% of U.S. electricity generation. Even in Germany, which gets more of its energy from solar than any other nation, its percentage

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use solar power to produce electricity without being near a power plant or connected to a grid. This is especially helpful in developing nations. In contrast, in developed nations, most PV systems are connected to the regional electric grid, and homeowners can sell excess solar energy to their local utility thanks to feed-in tariffs or net metering.

The development and deployment of solar systems is pro- ducing many new green-collar jobs. Currently, among major energy sources, PV technology employs the most people per unit energy output.

Finally, a major advantage of solar energy over fossil fuels is that it does not pollute the air with greenhouse gas emis- sions and other air pollutants. The manufacture of photo- voltaic cells does currently require fossil fuel use, but once up and running, a PV system produces no emissions.

Location, timing, and cost can be drawbacks Solar energy currently has three major disadvantages. One is that not all regions are sunny (FIGURE 16.13). People in cities such as Seattle might find it difficult to harness enough sun- light most of the year to rely on solar energy. Another is that solar energy is an intermittent resource. Daily or seasonal variation in sunlight can limit stand-alone solar systems if storage capacity in batteries or fuel cells is not adequate or if backup power is not available from a municipal electric grid. Pumped-storage hydropower can sometimes help compen- sate for periods of low solar power production.

The primary disadvantage of current solar technology is the up-front cost of the equipment. Because of the investment

(FIGURE 16.12). China leads the world in yearly production of PV cells, followed by Germany and Japan. Germany leads the world in installation of PV technology, and German rooftops host over half of all PV cells in the world. Germany’s invest- ment began in 1998 when Hermann Scheer spearheaded a “100,000 Rooftops” program to install PV panels atop 100,000 German roofs. The popular program easily surpassed this goal. The United States ranks fifth in production of PV cells. Recent federal tax credits and state-level initiatives may help the United States recover the leadership it lost to other nations in this technology, but China is moving faster and may soon dominate the market.

As production of PV cells increases, prices are falling (see Figure 16.12). At the same time, efficiencies are increasing, making each unit more powerful. Throughout the world, use of solar technology should continue to increase as prices fall, technologies improve, and governments enact economic in- centives to spur investment.

Solar energy offers many benefits The fact that the sun will continue burning for another 4–5 billion years makes it inexhaustible as an energy source for human civilization. Moreover, the amount of solar energy reaching Earth should be enough to power our civilization once we develop technology adequate to harness it. These advantages of solar energy are clear, but the technologies themselves also provide benefits. PV cells and other solar technologies use no fuel, are quiet and safe, contain no moving parts, require little maintenance, and do not require a turbine or generator to create electricity. An average unit can produce energy for 20–30 years.

Solar systems also allow for local, decentralized control over power. Homes, businesses, and isolated communities can

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FIGURE 16.12  Global production of PV cells has been growing exponentially, and minimum prices have fallen rapidly. Data from REN21, 2011. Renewables 2011: Global status report. Paris: REN21 Secretariat;

European Photovoltaic Industry Association; and U.S. Department of Energy.

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FIGURE 16.13  Some locations receive more sunlight than oth- ers, so harnessing solar energy is more profitable in some areas than in others. In the United States, many areas of Alaska and the Pacific Northwest receive only 3–4 kilowatt-hours per square meter per day, whereas most areas of the Southwest receive 6–7 kilowatt- hours per square meter per day. Data from National Renewable Energy Laboratory, U.S. Department of Energy.

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cost, solar power remains the most expensive way to produce electricity. However, declines in price and improvements in ef- ficiency of solar technologies so far are encouraging, even in the absence of significant funding from government and industry. At their advent in the 1950s, solar technologies had efficiencies of around 6% while costing $600 per watt. Today, PV cells are showing up to 20% efficiency commercially and 40% efficiency in lab research, suggesting that future solar cells could be more efficient than any energy technologies we have today. Solar systems are becoming less expensive and now can sometimes pay for themselves in 10–20 years or less. After that time, they provide energy virtually for free as long as the equipment lasts.

WIND ENERGY Wind energy—energy derived from the movement of air—is really an indirect form of solar energy because it is the sun’s differential heating of air masses on Earth that causes wind to blow. We can harness power from wind by using wind tur- bines, mechanical assemblies that convert wind’s kinetic en- ergy (p. 29), or energy of motion, into electrical energy.

Wind turbines convert kinetic energy to electrical energy Wind blowing into a turbine turns the blades of the ro- tor, which rotate machinery inside a compartment called a nacelle, which sits atop a tall tower (FIGURE 16.14). Inside the nacelle are a gearbox and a generator, as well as equipment to monitor and control the turbine’s activity. Today’s towers average 80 m (260 ft) in height, and the largest are taller than a football field is long. Higher is generally better, to minimize turbulence (and potential damage) while maximizing wind speed. Most rotors consist of three blades and measure 80 m (260 ft) across. Engineers design turbines to yaw, or rotate back and forth in response to changes in wind direction, en- suring that the motor faces into the wind at all times. They also design them to begin turning at specified wind speeds to harness wind energy as efficiently as possible. Turbines are often erected in groups called wind farms. The world’s largest wind farms contain hundreds of turbines spread across the landscape.

Wind power is growing fast Like solar energy, wind provides just a small proportion of the world’s power needs, but wind power is growing fast— doubling every three years (FIGURE 16.15). Five nations account for three-quarters of the world’s wind power output (FIGURE 16.16), but dozens of nations now produce wind pow- er. Germany had long produced the most, but the United States overtook it in 2008, and China surpassed the United States two years later. Texas accounts for the most wind power generated of all U.S. states. Denmark leads the world in obtaining the greatest percentage of its energy from wind power; in this small European nation, wind farms supply one-fifth of elec- tricity needs.

Experts agree that wind power’s rapid growth will con- tinue, because only a small portion of this resource is cur-

FIGURE 16.14  A wind turbine converts wind’s energy of motion into electrical energy. Wind causes the blades of a wind turbine to spin, turning a shaft that extends into the nacelle that is perched atop the tower. Inside the nacelle, a gearbox converts the rotational speed of the blades, which can be up to 20 revolutions per minute (rpm) or more, into much higher rotational speeds (over 1,500 rpm). These high speeds provide adequate motion for a gen- erator inside the nacelle to produce electricity.

Blades

Nacelle Tower

Gearbox (increases rotational

speed of blades)

Generator (produces electricity)

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FIGURE 16.15  Global production of wind power has been dou- bling every three years in recent years, and minimum prices have fallen rapidly. Data from REN21, 2011. Renewables 2011: Global status report. Paris: REN21 Secretariat; Global Wind Energy Council, 2010. Global

wind 2009 report; and U.S. Department of Energy. Price data are for Class 4

wind; stronger winds lead to cheaper prices.

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FIGURE 16.17  More and more wind farms are being developed offshore, because offshore winds tend to be stronger yet less tur- bulent. This Danish offshore wind farm is one of several that help provide over 20% of Denmark’s electricity.

rently being tapped and because wind power at favorable locations already generates electricity nearly as cheaply as do fossil fuels. A 2008 report by a consortium of govern- ment, industry, and environmental experts outlined how the United States could meet fully one-fifth of its electrical demands with wind power by 2030.

Offshore sites hold promise Wind speeds on average are roughly 20% greater over water than over land. There is also less air turbulence over water. For these reasons, offshore wind turbines are becoming pop- ular (FIGURE 16.17). Costs to erect and maintain turbines in water are higher, but the stronger, less turbulent winds make offshore wind potentially more profitable.

In the United States, no offshore wind farms have yet been constructed, but development of the first was given U.S.

U.S. (20.7%)

Germany (14.0%)

Rest of world (26.2%)

India (6.7%)

China (21.8%)

Spain (10.6%)

(a) Percentage of global wind power in each nation FIGURE 16.16  Most of the world’s fast-growing wind-power generating capacity is concentrated in a handful of countries, led by China, the United States, and Germany. Data from Global Wind Energy Council, 2011. Global wind 2010 report. GWEC, Brussels, Belgium.

government approval in 2010 after nine years of debate. The Cape Wind offshore wind farm, if constructed, will feature 130 turbines rising from Nantucket Sound 8 km (5 mi) off the coast of Cape Cod in Massachusetts. In announcing the government’s approval, U.S. Interior Secretary Ken Salazar predicted that it would be “the first of many projects up and down the Atlantic coast.”

Wind power has many benefits Like solar power, wind power produces no emissions once the equipment is manufactured and installed. As a replacement for fossil fuel combustion in the average U.S. power plant, running a 1-megawatt wind turbine for 1 year prevents the release of more than 1,500 tons of carbon dioxide, 6.5 tons of sulfur dioxide, 3.2 tons of nitrogen oxides, and 60 lb of mercury, according to the U.S. Environmental Protection Agency. The amount of carbon pollution that all U.S. wind turbines together prevent from entering the atmosphere is greater than the emissions from 7.5 million cars, or from combusting the cargo of a 600-car freight train of coal each and every day.

Wind power, under optimal conditions, appears con- siderably more efficient than conventional power sources in its energy returned on investment (EROI; p. 328). One study found that wind turbines produce 23 times more energy than they consume. For nuclear energy, the ratio was 16:1; for coal it was 11:1; and for natural gas it was 5:1.

Wind turbine technology can be used on many scales, from a single tower for local use to farms of hundreds that supply large regions. Small-scale turbine development can help make local areas more self-sufficient, just as solar energy can. Another benefit of wind power is that farmers and ranch- ers can lease their land for wind development. A single large turbine can bring in $2,000 to $4,500 in annual royalties while occupying just a quarter-acre of land. Because each turbine takes up only a small area, most of the land can still be used for farming or ranching. Royalties from the wind power company provide the farmer or rancher revenue while also increasing property tax income for their rural community.

Lastly, wind power creates job opportunities (FIGURE 16.18). The American Wind Energy Association estimates that over 85,000 Americans are now employed in the wind indus- try. More than 100 colleges and universities offer programs and degrees that train people in the skills needed for jobs in wind power and other renewable energy fields.

Wind power has some downsides Wind is an intermittent resource; we have no control over when wind will occur. This is a major problem, but is less- ened if wind is one of several sources contributing to a util- ity’s power generation. Pumped-storage hydropower can sometimes help compensate during windless times. Moreo- ver, batteries or hydrogen fuel can store energy generated by wind and release it later when needed.

Just as wind varies from time to time, it varies from place to place; some areas are windier than others. Resource plan- ners and wind power companies study wind patterns closely before planning a wind farm. Meteorological research has given us data with which to judge prime areas for locating

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wind farms. A map of average wind speeds across the Unit- ed States (FIGURE 16.19A) reveals that mountainous regions are best, along with areas of the Great Plains. Based on such information, the wind power industry has located much of its generating capacity in states with high wind speeds (FIGURE 16.19B) and is seeking to expand in the Great Plains and mountain states.

Good wind resources, however, are not always near pop- ulation centers that need the energy. Most of North Ameri- ca’s people live near the coasts, far from the Great Plains and mountain regions that have the best wind resources. Thus, transmission networks would need to be greatly expanded to get wind power to where people live.

When wind farms are proposed near population cent- ers, local residents often oppose them. Turbines are generally located in exposed, conspicuous sites, and some people object to wind farms for aesthetic reasons, feeling that the structures clutter the landscape. Wind turbines also pose a hazard to birds and bats, which are killed when they fly into the rotat- ing blades.FIGURE 16.18  As the wind power industry expands, it is becom-

ing a major source of new green-collar jobs.

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WA (2,356)

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DE (2)

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AZ (128)

MO (459)

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IN (1,339)

FIGURE 16.19  Meteorologists have measured wind speed to calculate the potential generating capacity from wind in different areas. The map in (a) shows average wind power across the United States, in watts per square meter at a height of 10 m (33 ft) above ground. Such maps are used to help guide placement of wind farms. The development of U.S. wind power so far is summarized in (b), which shows the megawatts of generating capacity developed in each state through April 2011. Sources: (a) Elliott, D.L., et al. 1987. Wind energy resource atlas of the United

States. Golden, CO: Solar Energy Research In-

stitute; (b) American Wind Energy Association.

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(b) Nesjavellir geothermal power station, Iceland

(a) Geothermal energy

Magma heats groundwater

Where natural fissures or cracks appear, heated water or steam surfaces in geysers or hot springs

2 Wells tap underground heated water or steam to turn turbines and generate power

Steam is cooled, condensed, and water is injected back into the aquifer to maintain pressure

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FIGURE 16.20  With geothermal energy (a), magma heats groundwater deep in the Earth �, some of which is let off naturally through surface vents such as geysers �. Geothermal facilities tap into heated water below ground and channel steam through turbines in buildings to generate elec- tricity �. After being used, the steam is often condensed, and the water is pumped back into the aquifer to maintain pressure �. At the Nesjavel- lir geothermal power station in Iceland (b), steam is piped from wells to a condenser at the plant, where cold water pumped from lakeshore wells is heated. The heated water is sent through an insulated pipeline to the capital city, where residents use it for washing and space heating.

GEOTHERMAL ENERGY Geothermal energy is thermal energy that arises from be- neath Earth’s surface. The radioactive decay of elements (p. 27) amid high pressures deep in the interior of our planet generates heat that rises to the surface through magma (mol- ten rock, p. 228) and through cracks and fissures. Where this energy heats groundwater, natural spurts of heated water and steam rise up from below and may erupt through the sur- face as terrestrial geysers or submarine hydrothermal vents (p. 260). Geothermal energy manifests itself at the surface in these ways only in certain regions.

We harness geothermal energy for heating and electricity Geothermal energy can be harnessed directly from gey- sers at the surface, but most often wells must be drilled down hundreds or thousands of meters toward heated

groundwater. Hot groundwater can be used directly for heating buildings and for driving industrial processes. The nation of Iceland heats nearly 90% of its homes through direct heating with piped hot water. Such direct use of naturally heated water is efficient and inexpensive, but it is feasible only where geothermal energy sources are read- ily available. Iceland has a wealth of geothermal resources because it is located along the spreading boundary of two tectonic plates (p. 228–229).

Geothermal power plants harness the energy of nat- urally heated underground water and steam to generate electricity (FIGURE 16.20). Generally, a power plant will bring water at temperatures of 150–370 °C (300–700 °F) or more to the surface and convert it to steam by lowering the pressure in specialized compartments. The steam is then used to turn turbines to generate electricity. The world’s largest geothermal power plants, The Geysers in northern California, provide enough electricity to supply 750,000 homes. The United States is the world leader in the use of

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less than air does, and ground-source heat pumps (GSHPs) make use of this fact. These pumps provide heating in the winter by transferring heat from the ground into buildings, and they provide cooling in the summer by transferring heat from buildings into the ground. This heat transfer is accom- plished with a network of underground plastic pipes that circulate water and antifreeze (FIGURE 16.22). Because heat is simply moved from place to place rather than being pro- duced using outside energy inputs, heat pumps can be highly energy-efficient.

More than 600,000 GSHPs are already used to heat U.S. homes. Compared to conventional electric heating and cooling systems, GSHPs heat spaces 50–70% more ef- ficiently, cool them 20–40% more efficiently, can reduce electricity use by 25%–60%, and can reduce emissions by up to 70%.

Geothermal power has benefits and limitations All forms of geothermal energy greatly reduce emissions rela- tive to fossil fuel combustion. Although geothermally heated water can release dissolved gases, including carbon dioxide, methane, ammonia, and hydrogen sulfide, these are gener- ally in small quantities, and facilities using the latest filtering technologies produce even fewer emissions.

Geothermal energy is renewable in that using it does not affect the amount of thermal energy produced underground. However, not every power plant we build to capture this en- ergy will be able to operate indefinitely. If a geothermal plant uses heated water more quickly than groundwater is recharged, the plant will eventually run out of water. This was occurring at The Geysers in California, so in response, operators began

FIGURE 16.21  Geothermal resources in the United States are greatest in the western states. This map shows water temperatures 3 km (1.9 mi) below ground. Although deep subterranean tempera- tures are greatest in the West, ground-source heat pumps can be used anywhere in the country. Data from Idaho National Laboratory.

200–250º C >250º C

150–200º C

100–150º C

50–100º C

<50º C

geothermal power, but only some U.S. regions have geo- thermal resources near the surface that can be readily used (FIGURE 16.21).

Heat pumps make use of temperature differences above and below ground Although heated groundwater is available only in certain areas, we can take advantage of the temperature differences that naturally exist between the soil and the air just about anywhere. Soil varies in temperature from season to season

In winter, soil underground is warmer than surface air. Water flowing through the pipes transfers heat from the ground to the house, warming the house.

In summer, soil underground is cooler than surface air. Water flowing through the pipes transfers heat from the house to the ground, cooling the house.

Heat pump may warm or cool air in ducts, water in tank, or radiant heating/cooling system under floor.

Heat pump

Underground pipes

Cool water

Warm water

FIGURE 16.22  Ground-source heat pumps provide an efficient way to heat and cool air and water in one’s home. A network of plastic pipes filled with water and antifreeze extend underground from the house. Soil is warmer than the air in the winter (left), and cooler than the air in the summer (right), so by running fluid between the house and the ground, these systems help adjust temperatures inside.

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Incoming waves enter chamber

The rise and fall of water level within the chamber compresses and decompresses the column of air above it

Air flow in both directions drives the turbine, generating power

Incoming waves

Rising and falling water column

Column of air Turbine and

generator

FIGURE 16.23  Coastal facilities can make use of energy from the motion of ocean waves. In one design, as waves are let into and out of a tightly sealed chamber �, the air inside is alternately compressed and decompressed �, creating air flow that rotates turbines � to generate electricity.

injecting municipal wastewater into the ground to replenish the supply. Moreover, patterns of geothermal activity in Earth’s crust shift naturally over time, so an area that produces hot groundwater now may not always do so. In addition, the water of many hot springs is laced with salts and minerals that corrode equipment and pollute the air. These factors may shorten the lifetime of plants, increase maintenance costs, and add to pollution.

The greatest limitation of geothermal electric power is that it is restricted to regions where we can tap the energy from naturally heated groundwater. Iceland, northern Cali- fornia, and Yellowstone National Park are rich in naturally heated groundwater, but most areas of the world are not. En- gineers are presently trying to overcome this limitation by developing enhanced geothermal systems (EGS), in which we drill deeply into dry rock, fracture the rock, and pump in cold water. The water becomes heated deep underground and is then drawn up through an outlet well and used to generate power. In theory we could use EGS widely in many locations. For instance, Germany has very little heated groundwater, but feed-in tariffs have enabled an EGS facility to operate profit- ably here. However, EGS also appears to trigger minor earth- quakes. Unless we can develop ways to use EGS safely without causing earthquakes, our use of geothermal power will remain more localized than solar, wind, biomass, or hydropower.

OCEAN ENERGY SOURCES The oceans are home to several underexploited energy sourc- es stemming from continuous natural processes. Of the four approaches being developed, three involve motion and one involves temperature.

We can harness energy from tides, waves, and currents Just as dams on rivers use f lowing fresh water to generate hy- droelectric power, we can use kinetic energy from the natural motion of ocean water to generate electrical power. The rise and fall of ocean tides (p. 257) twice each day moves large amounts of water past any given point on the world’s coast- lines. Differences in height between low and high tides are especially great in long, narrow bays such as Alaska’s Cook Inlet or the Bay of Fundy between New Brunswick and Nova Scotia. Such locations are best for harnessing tidal energy, which is done by erecting dams across the outlets of tidal ba- sins. As tidal currents pass through the dam, water turns tur- bines to generate electricity.

The world’s largest tidal generating station, the La Rance facility in France, has operated for over 45 years. Smaller fa- cilities operate in China, Russia, and Canada. San Francisco is seeking to build a tidal energy station under the Golden Gate Bridge, and New York City is considering establishing one in the East River. Tidal stations release few or no pollut- ant emissions, but they can affect the ecology of estuaries and tidal basins.

People are also working to harness the motion of ocean waves and convert their mechanical energy into electricity. Many designs for machinery to harness wave energy have

been invented, but few have been adequately tested. Some de- signs for offshore facilities involve floating devices that move up and down with the waves. Some designs for onshore facili- ties funnel waves from large areas into narrow channels and elevated reservoirs, from which water then flows out, generat- ing electricity as hydroelectric dams do. Other coastal designs use rising and falling waves to push air into and out of cham- bers, turning turbines (FIGURE 16.23). No commercial wave energy facilities are operating yet, but demonstration projects exist in Europe, Japan, and Oregon.

A third way to harness marine kinetic energy is to use the motion of ocean currents (p. 255), such as the Gulf Stream. Devices that look like underwater wind turbines have been erected in European waters to test this idea.

The ocean stores thermal energy Each day the tropical oceans absorb an amount of solar ra- diation equivalent to the heat content of 250 billion barrels of oil—enough to provide 20,000 times the electricity used daily in the United States. The ocean’s sun-warmed surface is warm- er than its deep water, and ocean thermal energy conversion (OTEC) approaches are based on this temperature gradient.

In one approach, warm surface water is piped into a fa- cility to evaporate chemicals, such as ammonia, that boil at low temperatures. These evaporated gases spin turbines to generate electricity. Cold water piped in from ocean depths then condenses the gases so they can be reused. In another approach, warm surface water is evaporated in a vacuum, and its steam turns turbines and then is condensed by cold water. Because ocean water loses salts as it evaporates, the water can be recovered, condensed, and sold as desalinized fresh water

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cells and of fuel consisting of hydrogen—the universe’s simplest and most abundant element—shows promise as a way to store considerable quantities of energy conveniently, cleanly, and effi- ciently. Like electricity and like batteries, hydrogen is an energy carrier, not a primary energy source. It carries energy that can be converted for use at later times and in different places.

Some yearn for a “hydrogen economy” Some energy experts envision that hydrogen fuel, together with electricity, could serve as the basis for a clean, safe, and efficient energy system. In such a system, electricity gener- ated from intermittent renewable sources, such as wind and solar energy, could be used to produce hydrogen. Fuel cells (FIGURE 16.24) would then use hydrogen to produce electrical energy as needed to power vehicles, computers, cell phones, home heating, and countless other applications.

Basing an energy system on hydrogen could alleviate dependence on foreign fuels and help fight climate change. For these reasons, governments are funding research into hy- drogen and fuel-cell technology, and automobile companies have developed vehicles that run on hydrogen. Today, Ger- many is one of several nations with hydrogen-fueled city buses (FIGURE 16.25).

Hydrogen fuel may be produced from water or from other matter Hydrogen gas (H2) does not tend to exist freely on Earth. In- stead, hydrogen atoms bind to other molecules, becoming in- corporated in everything from water to organic compounds. To obtain hydrogen gas for fuel, we must force these substanc- es to release their hydrogen atoms, and this requires an input

HYDROGEN Each of the renewable energy sources we have discussed can be used to generate electricity more cleanly than can fossil fuels. However, electricity cannot be stored easily in large quantities for use when and where it is needed. This is why most vehicles rely on gasoline from oil for their power. The development of fuel

for drinking or agriculture. Research on OTEC systems has been conducted in Hawaii and elsewhere, but costs remain high, and so far no facility operates commercially.

Your Nation’s Energy? You are the presi- dent of a nation the size of Germany, and your nation’s congress is calling on you to propose

a national energy policy. Your country is located along a tropical coastline. Your geologists do not yet know whether there are fossil fuel deposits or geothermal resources under your land, but your country gets a lot of sunshine and a fair amount of wind, and broad, shallow shelf regions line its coasts. Your nation’s population is moderately wealthy but is growing fast, and importing fossil fuels from other nations is becoming expensive.

What approaches would you propose in your energy policy? Name some specific steps you would urge your congress to fund. Are there trade relationships you would seek to establish with other countries? What questions would you fund your nation’s scientists to research?

H+

– +

The electrons move from the negative electrode to the positive electrode, creating a current and generating electricity

Hydrogen molecules are stripped of electrons at the negative electrode, leaving hydrogen ions (protons, H+)

Water is formed when oxygen combines with the protons and electrons that flow from the positive electrode

The protons traverse the membrane

Hydrogen fuel, H2 Oxygen,O2

Water, H2O

Positive electrode

Negative electrode

Proton (H+) exchange membrane

FIGURE 16.24  Hydrogen fuel drives electricity generation in a fuel cell, creating water as a waste product. First, atoms of hydro- gen are split � into protons and electrons. The protons, or hydrogen ions �, pass through a proton exchange membrane. The electrons, meanwhile, move from a negative electrode to a positive one via an external circuit �, creating a cur- rent and generating electricity. The protons and electrons then combine with oxygen � to form water molecules.

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Hydrogen and fuel cells have costs and benefits One major drawback of hydrogen at this point is a lack of in- frastructure. To convert a nation like Germany or the United States to hydrogen would require massive and costly devel- opment of facilities to produce, store, transport, and provide the fuel.

Another concern is that some research suggests that leak- age of hydrogen from its production, transport, and use could potentially deplete stratospheric ozone (pp. 279, 289–291), and lengthen the atmospheric lifetime of the greenhouse gas methane. Research into these questions is ongoing, because scientists do not want society to switch from fossil fuels to hy- drogen without first knowing the risks.

Hydrogen’s benefits include the fact that we will never run out of it, because it is the most abundant element in the universe. Hydrogen can be clean and nontoxic to use, and— depending on its source and the source of electricity for its extraction—it may produce few greenhouse gases and other pollutants. Water and heat are the only waste products from a hydrogen fuel cell, along with negligible traces of other com- pounds. In terms of safety for transport and storage, hydrogen can catch fire and explode, but if kept under pressure, it may not be much more dangerous than gasoline in tanks.

Hydrogen fuel cells are energy-efficient. Depending on the type of fuel cell, 35–70% of the energy released in the re- action can be used. If the system is designed to capture heat as well as electricity, then the energy efficiency of fuel cells can rise to 90%. These rates are comparable or superior to most nonrenewable alternatives. Fuel cells are also silent and nonpolluting. Unlike batteries (which also produce electricity through chemical reactions), fuel cells will generate electric- ity whenever hydrogen fuel is supplied, without ever needing recharging. For all these reasons, hydrogen fuel cells may soon be used to power cars, much as they are already powering bus- es operating on the streets of some German cities.

of energy. Scientists are studying several potential ways of pro- ducing hydrogen. In electrolysis, electricity is input to split hydrogen atoms from the oxygen atoms of water molecules:

2H2O 2H2 + O2 Electrolysis produces pure hydrogen, and it does so with-

out emitting the carbon- or nitrogen-based pollutants of fossil fuel combustion. However, whether this strategy for produc- ing hydrogen will cause pollution depends on the source of the electricity used for the electrolysis. If coal is burned to gen- erate the electricity, then the process will not reduce emissions compared with reliance on fossil fuels. The “cleanliness” of a future hydrogen economy, therefore, depends largely on the source of electricity used in electrolysis.

The environmental impact of hydrogen production will also depend on the source material for the hydrogen. Besides water, hydrogen can be obtained from biomass and from fos- sil fuels. Obtaining hydrogen from these sources generally requires less energy input but results in emissions of carbon- based pollutants. For instance, extracting hydrogen from the methane (CH4) in natural gas entails producing one molecule of the greenhouse gas carbon dioxide for every four molecules of hydrogen gas:

CH4 + 2H2O 4H2 + CO2 Thus, whether a hydrogen-based energy system is clean-

er than a fossil fuel system depends on how the hydrogen is extracted.

Once isolated, hydrogen gas can be used as a fuel to pro- duce electricity within fuel cells. The chemical reaction involved in a fuel cell is simply the reverse of that shown for electrolysis; an oxygen molecule and two hydrogen molecules each split so that their atoms can bind and form two water molecules:

2H2 + O2 2H2O

Figure 16.24 shows how this occurs within one common type of fuel cell.

Hydrogen tanks1

Fuel cell supply unit

Fuel cell stacks

3 Cooling units

Air conditioning unit

5 Electric motor6

Water vapor exhaust

FIGURE 16.25  In one type of hydrogen-fueled bus operating in some German cities, hydrogen is stored in nine fuel tanks �. The fuel cell supply unit � controls the flow of hydrogen, air, and cooling water into the fuel cell stacks �. Cooling units � and the air conditioning unit � dissipate waste heat produced by the fuel cells. Electricity generated by the fuel cells is changed from direct current (DC) to alternating current (AC) by an inverter, and it is transmit- ted to the electric motor �, which powers the operation of the bus. The vehicle’s exhaust � consists simply of water vapor.

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➤ CONCLUSION Rising concern over air pollution, global climate change, health impacts, and security risks resulting from our reliance on fossil fuels—as well as anxiety over dwindling supplies of oil and natural gas—have convinced many people that we need to shift to renewable energy sources that pollute far less and that will not run out. Bioenergy sources include tradi- tional fuelwood, as well as newer biofuels and various means of generating biopower. These sources can be carbon-neutral but are not all strictly renewable. Hydropower is clean and

renewable, but it is nearing its maximal extent of use and can involve substantial ecological impacts. Renewable sources with promise for sustaining our civilization far into the fu- ture without greatly degrading our environment include solar energy, wind energy, geothermal energy, and ocean en- ergy sources. By using electricity from renewable sources to produce hydrogen fuel, we may be able to use fuel cells to pro- duce electricity when and where it is needed, helping to create a nonpolluting and renewable transportation sector.

T E S T I N G Y O U R C O M P R E H E N S I O N

1. About how much of our energy now comes from renew- able sources? What is the most prevalent form of renew- able energy we use? What form of renewable energy is most used to generate electricity?

2. What factors and concerns are causing renewable energy sectors to expand? Which two renewable sources are ex- periencing the most rapid growth?

3. List five sources of bioenergy. What is the world’s most- used source of bioenergy? How does bioenergy use differ between developed and developing nations?

4. Contrast two major approaches to generating hydroelec- tric power. List one benefit and one negative impact of hydropower.

5. Contrast passive and active solar heating, and give an ex- ample of each. Now explain how photovoltaic (PV) cells function and are used.

6. Describe how modern wind turbines generate electricity. What factors affect where we place wind turbines?

7. Define geothermal energy, and explain three main ways in which it is obtained and used. Describe one sense in which it is renewable, and one sense in which it is not renewable.

8. List and describe four approaches for obtaining energy from ocean water.

9. For each major type of renewable energy (bioenergy, hy- dropower, solar, wind, geothermal, and ocean), brief ly describe at least one advantage and one disadvantage of its use, relative to use of fossil fuels.

10. How is hydrogen fuel produced? Is this a clean process? What factors determine the amount of pollutants hydro- gen production will emit?

S E E K I N G S O L U T I O N S

1. Explain how Germany accelerated its development of renewable energy by establishing a system of feed-in tar- iffs. Do you think the United States should adopt a simi- lar system? Why or why not?

2. For each source of renewable energy discussed in this chapter, what factors are standing in the way of an expe- dient transition from fossil fuel use? What could be done in each case to ease a shift to these renewable sources?

3. Do you think we can develop renewable energy resources to replace fossil fuels without great social, economic, and environmental disruption? What steps would we need to take? Will market forces alone suffice to bring about this transition, or will we also need government? Do you think such a shift will be good for our economy? Why or why not?

4. THINK IT THROUGH You are an investor looking to invest in alternative energy. You are considering buying stock in companies that (1) build corn ethanol refineries, (2) are developing algae farms for biofuels, (3) construct

turbines for hydroelectric dams, (4) produce PV solar panels, (5) install wind turbines, and (6) plan to build a wave energy facility. For each of these companies, what questions would you research before deciding how to in- vest your money? How do you expect you might appor- tion your investments, and why?

5. THINK IT THROUGH You are the CEO of a company that develops wind farms. Your staff is presenting you with three options, listed below, for sites for your next development. Describe at least one likely advantage and at least one likely disadvantage you would expect to encounter with each option. What further informa- tion would you like to know before deciding which to pursue? ▶ Option A: A remote rural site in North Dakota ▶ Option B: A ridge-top site among the suburbs of

Philadelphia ▶ Option C: An offshore site off the Florida coast

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ter. Now refer to Figure 16.13 on p. 368, and estimate the area and cost of the PV panels needed to provide all of the residential electricity used by each group in the table.

C A L C U L A T I N G E C O L O G I C A L F O O T P R I N T S

Assume that average per capita residential consumption of electricity is 12 kilowatt-hours per day, that photovoltaic cells have an electrical output of 15% incident solar ra- diation, and that PV panels cost $1,000 per square me-

Area of photovoltaic cells Cost of photovoltaic cells

You A resident of Arizona A resident of Alaska Total for all U.S. residents

3. The purchase price of a photovoltaic system is consider- able. What other costs and benefits should you consider, in addition to the purchase price, when contemplating “going solar”?

1. What additional information would you need to increase the accuracy of your estimates for the areas in the table above?

2. Considering the distribution of solar radiation in the United States, where do you think it will be most feasible to greatly increase the percentage of electricity generated from photovoltaic solar cells?

Go to www.masteringenvironmentalscience.com for homework assignments, practice quizzes, Pearson eText, and more.

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THEN: Fresh Kills Landfill in operation NOW: Fresh Kills Landfill site today

Fresh Kills Landfill, Staten Island, New York

17 Managing Our WasteUpon completing this chapter, you will be able to: � Summarize and compare the types of waste we generate � List the major approaches to managing waste � Delineate the scale of the waste dilemma � Describe conventional waste disposal methods: landfills and incineration � Evaluate approaches for reducing waste: source reduction, reuse, composting, and recycling � Discuss industrial solid waste management and principles of industrial ecology � Assess issues in managing hazardous waste

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CE N T R A L C A S E S T U DY

Transforming New York’s Fresh Kills Landfill “An extraterrestrial observer might conclude that conversion of raw materials to wastes is the real purpose

of human economic activity.” —Gary Gardner and Payal Sampat, Worldwatch Institute

“Recycling is one of the best environmental success stories of the late 20th century.” —U.S. Environmental Protection Agency

T he closure of a landfill is not the kind of event that normally draws politicians and the

press, but the Fresh Kills Landfill was no ordinary dump. Said to be the largest hu-

man-made structure on Earth, Fresh Kills was the primary repository of New York

City’s garbage for half a century. On March 22, 2001, New York City Mayor Rudolph Giuliani

and New York Governor George Pataki were on hand to celebrate as a barge arrived on the

shore of Staten Island and dumped the final load of trash at Fresh Kills.

The landfill’s closure was a blessing for Staten Island’s 450,000 residents, who had long viewed Fresh Kills as a foul-smelling eyesore, health threat, and civic blemish. The 890-ha (2,200-acre) landfill featured six gigantic mounds of trash and soil. The highest, at 69 m (225 ft), was higher than the nearby Statue of Liberty.

New York City had gran- diose plans for the site. It planned to transform the old landfill into a world-class public park—a verdant land- scape of ball fields, playgrounds, jogging trails, roll- ing hills, and wetlands teeming with wildlife. Nearly three times bigger than Manhattan’s Central Park, the site hosted the region’s largest remaining com- plex of salt marshes and freshwater creeks, while the mounds offered panoramic views of the Manhattan skyline. The city sponsored an international competi- tion to select a landscape architecture firm to design plans for the new park.

Meanwhile, with its only landfill closed, New York City began exporting its waste—and found itself pay- ing contractors exorbitant prices to haul its garbage away one truckload at a time. In the years following the Fresh Kills closure, trucks full of trash rumbled through

neighborhood streets, car- rying 12,000 tons of waste each day bound for 26 dif- ferent landfills and incin- erators in New York, New Jersey, Virginia, Pennsyl- vania, and Ohio. The city sanitation department’s ex- penses doubled, and budg- et woes caused the city to scale back its recycling pro- gram. Some New Yorkers suggested reopening Fresh Kills.

The landfill was reo- pened, but not for a reason anyone could have fore- seen. After the September 11, 2001, terrorist attacks, the 1.8 million tons of rubble from the collapsed World Trade Center towers, including unrecoverable human remains, was taken by barge to Fresh Kills. A monument will be erected as part of the new park.

Today, park development is forging ahead. Roads, ball fields, sculptures, and in-line skating rinks are be- ing designed. Wetlands are being restored. People will be able to bicycle on trails alongside the region’s largest estuary and reach stunning vistas atop the hills. Recreation areas named Owl Hollow Fields and Schmul Park should open in 2011, and work has begun on a parcel overlooking an adjacent wildlife refuge. The full conversion of Fresh Kills Landfill into Fresh Kills

Atlantic Ocean

CANADA

NEW YORK

UNITED STATES

Fresh Kills Landfill

Staten Island

New York City Long Island

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Park—one of the largest public works projects in the world—will take 30 years. But in the end this longtime symbol of waste will be transformed into a world-class center for recreation and urban ecological restoration.

Meanwhile, the city continues to truck its trash to out-of-state landfills. It has also built a transfer station at Fresh Kills to compact the waste and ship it outward by barge and railroad, at less expense. There is no true “away” for the things we do not reuse or recycle. For New Yorkers—and for the rest of us—the waste we discard needs to go somewhere. �

APPROACHES TO WASTE MANAGEMENT As the world’s population rises, and as we produce and con- sume more material goods, we generate more waste. Waste refers to any unwanted material or substance that results from a human activity or process.

For management purposes, we divide waste into several main categories. Municipal solid waste is nonliquid waste that comes from homes, institutions, and small businesses. Industrial solid waste includes waste from production of con- sumer goods, mining, agriculture, and petroleum extraction and refining. Hazardous waste refers to solid or liquid waste that is toxic, chemically reactive, flammable, or corrosive. Another type of waste is wastewater (pp. 270, 272–273), water we use

in our households, businesses, industries, or public facilities and drain or flush down our pipes, as well as the polluted run- off from streets and storm drains.

We have several aims in managing waste Waste can degrade water quality, soil quality, air quality, and human health. Waste is also unpleasant aesthetically. Moreo- ver, waste is a measure of inefficiency, so reducing waste can save money and resources. For all these reasons, waste man- agement has become a vital pursuit.

There are three main components of waste management:

1. Minimizing the amount of waste we generate 2. Recovering discarded materials and finding ways to recy-

cle them 3. Disposing of waste safely and effectively

Minimizing waste at its source—called source reduction— is the preferred approach. There are several ways to reduce the amount of waste that enters the waste stream, the flow of waste as it moves from its sources toward disposal destinations (FIGURE 17.1). In this chapter we first examine how the three major approaches are used to manage municipal solid waste, and then we address industrial solid waste and hazardous waste.

MUNICIPAL SOLID WASTE Municipal solid waste is waste we generate in homes, public facilities, and small businesses. It is what we commonly refer to as “trash” or “garbage.”

Waste stream with steps to reduce waste Make industrial practices more efficient

Waste stream without steps to reduce waste

Waste disposal (landfill, incinerator)

Minimize packaging for products

Purchase “green” consumer products

Compost materials at home

Recycle items

Reuse items

Municipal composting

FIGURE 17.1  The most effective way to manage waste is to minimize the amount of material that enters the waste stream. To do this, manufacturers can increase efficiency, and consumers can buy “green” products that have minimal packaging or are produced in ways that minimize waste.

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Waste generation is rising In the United States since 1960, waste generation (before recovery) has increased by 2.8 times, and per-person waste generation has risen by 62%. Paper, food scraps, yard trim- mings, and plastics are the principal components of munici- pal solid waste in the United States, together accounting for 68% of what enters the waste stream (FIGURE 17.2A). Paper is recycled at a high rate and yard trimmings are composted at a high rate, so as a result, after recycling and composting reduce the waste stream, food scraps and plastics are left as the larg- est components of U.S. municipal solid waste (FIGURE 17.2B).

Most municipal solid waste comes from packaging and nondurable goods (products meant to be discarded after a short period of use). In addition, consumers throw away old durable goods and outdated equipment as they purchase new products. Plastics, which came into wide consumer use only after 1970, have accounted for the greatest relative increase in the waste stream during the last several decades.

As we acquire more goods, we generate more waste. In 2009, U.S. citizens produced 243 million tons of municipal solid waste (before recovery), over 700 kg (1,500 lb) per per- son. The average American generates 2.0 kg (4.3 lb) of trash per day—considerably more than people of most other devel- oped nations. The relative wastefulness of the U.S. lifestyle, with its excess packaging and reliance on nondurable goods, has caused critics to label the United States “the throwaway society.” U.S. waste generation decreased slightly between 2007 and 2009, but this reflected reduced consumption dur- ing economic recession.

In developing nations, people consume less and generate considerably less waste. However, consumption is intensify- ing in developing nations as they become more affluent, and these nations are creating more and more waste. The increase

in waste reflects rising material standards of living, but it also results from an increase in packaging, manufacturing of non- durable goods, and production of inexpensive, poor-quality goods that wear out quickly. As a result, trash is piling up and littering the landscapes of countries from Mexico to Kenya to Indonesia. Like U.S. consumers in the “throwaway society,” wealthy consumers in developing nations often discard items that can still be used. In fact, at many dumps and landfills in the developing world, poor people support themselves by selling items they scavenge (FIGURE 17.3).

Wealthier nations can afford to invest more in waste collection and disposal, so they are often better able to manage

Yard trimmings

Metals

Rubber, leather, and textiles

Wood

Glass (5.5%)

Other (4.5%)

Paper 16.1%

8.3%

Food scraps 20.8%

Plastics 17.2%

8.5%

10.7%

8.5%

Rubber, leather, and textiles

Wood

Glass

Other (3.5%)

Paper 28.2%

Yard trimmings

13.7%

Food scraps 14.1%

Plastics 12.3%

Metals 8.6%

8.3%

6.5%

4.8%

(a) Before recycling and composting (b) After recycling and composting

FIGURE 17.3  Tens of thousands of people used to scavenge each day from this dump outside Manila in the Philippines, find- ing items for themselves and selling material to junk dealers for 100–200 pesos (U.S. $2–$4) per day. That so many people could support themselves this way testifies to the immense amount of usable material discarded by wealthier people. The dump was closed in 2000 after an avalanche of trash killed hundreds of people.

FIGURE 17.2  Paper products comprise the largest component of the municipal solid waste stream in the United States by weight (a), followed by food scraps, yard trimmings, and plastics. After recycling and composting re- moves many items (b), the waste stream becomes one-third smaller (as shown by the smaller size of the pie chart). Food scraps are now the largest contributor, followed by plastics, because so much paper is recycled and yard waste is composted. Data from U.S. Environmental Protection Agency, 2010. Municipal solid waste in the United States: 2009 facts and figures. EPA, Washington, D.C.

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their waste and minimize impacts on human health and the en- vironment. Moreover, in many industrialized nations, recovery (recycling and composting) is taking care of an increasingly larger portion of waste (FIGURE 17.4). We will examine reduc- tion, reuse, recycling, and composting shortly, but let’s first as- sess how we dispose of waste.

Sanitary landfills are regulated with health and environmental guidelines In modern sanitary landfills, waste is buried in the ground or piled up in large mounds engineered to prevent waste from contaminating the environment and threatening public

health (FIGURE 17.5). Most municipal landfills in the United States are regulated locally or by the states, but they must meet national standards set by the U.S. Environmental Protection Agency (EPA) under the federal Resource Conservation and Recovery Act (RCRA), enacted in 1976 and amended in 1984.

In a sanitary landfill, waste is partially decomposed by bacteria and compresses under its own weight to take up less space. Soil is layered along with the waste to speed decom- position, reduce odor, and lessen infestation by pests. Some infiltration of rainwater into the landfill is good, because it en- courages biodegradation by aerobic and anaerobic bacteria— yet too much is not good, because contaminants can escape if water carries them out.

1960 1965 1970 1975 1980

Year

1985 1990 1995 2000 2005 2009

Recovery for composting

Recovery for recycling

Combustion

Landfill, other disposal

250

200

150

100

U .S

. m

u n

ic ip

al s

o lid

w as

te ( m

ill io

n s

o f

to n

FIGURE 17.4  Since the 1980s, recycling and composting have grown in the United States, allowing a smaller proportion of waste to go to landfills. As of 2009, 54% of U.S. municipal solid waste was going to landfills and 12% to incinerators, whereas 34% was being recovered for composting and recycling. Data from U.S. Environmental Protection

Agency, 2010. Municipal solid waste in the

United States: 2009 facts and figures. EPA,

Washington, D.C.

Groundwater monitoring well

Leachate treatment system

Methane gas recovery well

Soil Solid waste

Aquifer

Compacted impermeable clay

Leachate collection pipes

Plastic liner

Gravel Granular drainage layer

FIGURE 17.5  Sanitary landfills are engineered to prevent waste from contaminating soil and groundwater. Waste is laid in a large depression lined with plastic and impervious clay designed to prevent liquids from leaching out. Pipes of a leachate col- lection system draw out these liquids from the bottom of the landfill. Waste is layered along with soil until the depression is filled, and it continues to be built up until the landfill is capped. Landfill gas produced by anaerobic bacteria may be recovered, and waste managers monitor groundwater for contamination.

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To protect against environmental contamination, U.S. regulations require that landfills be located away from wet- lands and earthquake-prone faults and be at least 6 m (20 ft) above the water table. The bottoms and sides of sanitary land- fills must be lined with heavy-duty plastic and 60–120 cm (2–4 ft) of impermeable clay to help prevent contaminants from seeping into aquifers. Sanitary landfills also have systems of pipes, collection ponds, and treatment facilities to collect and treat leachate , liquid that results when substances from the trash dissolve in water as rainwater percolates downward. Once a landfill is closed, it is capped with an engineered cover consisting of layers of plastic, gravel, and soil, and manag- ers are required to maintain leachate collection systems for 30 years.

The Fresh Kills Landfill was considered a model for advanced landfill technology at the time of its construction, but it was built before most of the EPA guidelines. As a re- sult, it caused some environmental contamination. How- ever, engineers have retrofitted the landfill with clay liners and a sophisticated leachate collection system. Three of the six mounds have been capped with a “final cover,” and the remaining mounds will soon be capped. Because these safeguards need to be maintained for 30 years after closure, designs for a public park at Fresh Kills have had to work around them.

In 1988 the United States had nearly 8,000 landfills, but today it has fewer than 2,000. Waste managers have consoli- dated the waste stream into fewer landfills of larger size. In many cities, landfills that were closed are now being convert- ed into public parks or other uses ( FIGURE 17.6 ). The Fresh Kills endeavor will be the world’s largest landfill conversion project, but such efforts date back at least to 1938, when an ash landfill at Flushing Meadows, in Queens, was redeveloped for the 1939 World’s Fair. The site subsequently hosted the United Nations and the 1964–1965 World’s Fair. Designated a park in 1967, today the site hosts Shea Stadium, the Queens Museum of Art, the New York Hall of Science, and the Queens

Botanical Garden, as well as playgrounds, wetlands, and fes- tival events.

Landfills have drawbacks Despite improvements in liner technology and landfill sit- ing, liners can be punctured, and leachate collection systems eventually cease to be maintained. Moreover, landfills are kept dry to reduce leachate, but dryness slows waste decom- position. In fact, the low-oxygen conditions of most landfills turns trash into a sort of time capsule. Researchers examin- ing landfill contents often find some of their contents per- fectly preserved, even after years or decades.

FIGURE 17.6  Old landfills, once properly capped, can serve other purposes. A number of them, such as Cesar Chavez Park in Berkeley, California, shown here, have been developed into areas for recreation.

FAQ

Q: How much does garbage decompose in a landfill? A: You might assume that a banana peel you throw in the trash will soon decay away to nothing in a landfill. However, it might just survive longer than you do! This is because surprisingly little decomposition occurs in landfills. Researcher William Rathje, nicknamed “the Indiana Jones of Solid Waste,” made a career out of burrowing into landfills and examining their contents to learn about what we consume and what we throw away. His research teams would routinely come across whole hot dogs, intact pastries that were decades old, and grass clippings that were still green. Newspapers 40 years old are often still legible, and researchers have used them to date layers of trash.

A second challenge with landfills is finding suitable areas to locate them, because most communities do not want them nearby. This not-in-my-backyard (NIMBY) reaction is one reason why New York City decided to export its waste—and why residents of states receiving that waste are increasingly protesting. As a result of the NIMBY syndrome, landfills are rarely sited in neighborhoods that are home to wealthy and educated people with the political clout to keep them out. In- stead, they are disproportionately sited in poor and minority communities, as environmental justice advocates (pp. 14–15 ) have frequently pointed out.

Incinerating trash reduces pressure on landfills Just as sanitary landfills are an improvement over open dumping, incineration in specially constructed facilities is an improvement over open-air burning of trash. Incineration , or combustion, is a controlled process in which garbage is burned at very high temperatures ( FIGURE 17.7 ). At incinera- tion facilities, waste is generally sorted and metals removed. Metal-free waste is chopped into small pieces and then is

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burned in a furnace. Incinerating waste reduces its weight by up to 75% and its volume by up to 90%.

The ash remaining after trash is incinerated contains toxic components and therefore must be disposed of in hazardous waste landfills (p. 395). Moreover, when trash is burned, hazardous chemicals—including dioxins, heavy met- als, and PCBs (Chapter 10)—can be created and released into the atmosphere. Such emissions caused a backlash against in- cineration from citizens concerned about health hazards.

Most developed nations now regulate incinerator emis- sions, some have banned incineration outright, and engineers have developed technologies to mitigate emissions. Scrubbers (see Figure 13.10, p. 286) chemically treat the gases produced in combustion to remove hazardous components and neutral- ize acidic gases, such as sulfur dioxide and hydrochloric acid, turning them into water and salt. Scrubbers generally do this either by spraying liquids formulated to neutralize the gases or by passing the gases through dry lime. Particulate matter, called fly ash, often contains some of the worst dioxin and heavy metal pollutants in incinerator emissions. To physically remove these tiny particles, facilities may use a system of huge filters known as a baghouse. In addition, burning garbage at especially high temperatures can destroy certain pollutants, such as PCBs. Even all these measures, however, do not fully eliminate toxic emissions.

We can gain energy from trash Incineration reduces the volume of waste, but it often serves to generate electricity as well. Most incinerators now are waste-to-energy (WTE) facilities that use the heat produced by waste combustion to boil water, creating steam that drives electricity generation or that fuels heating systems. When burned, waste generates approximately 35% of the energy generated by burning coal.

Combustion in WTE plants is not the only way to gain energy from waste. Deep inside landfills, bacteria decompose waste in an oxygen-deficient environment. This anaerobic decomposition produces landfill gas, a mix of gases consist- ing of roughly half methane (pp. 28, 329). Landfill gas can

Waste storage pit

Crane

Furnace

Water

Ash

Boiler

Scrubber Baghouse

GeneratorTurbine

542

Stack

Wastewater and ash for treatment or

disposal in landfill

Environmental Justice? Do you know where your trash goes? Where is your landfill or incinerator located? Are the people who live closest to the facility wealthy, poor, or middle

class? What race or ethnicity are they? Do you know whether the people of this neighborhood protested against the introduction of the landfill or incinerator?

FIGURE 17.7  Incinerators reduce the volume of solid waste by burning it but may emit toxic compounds into the air. Many incinerators are waste-to-energy (WTE) facilities that use the heat of combustion to generate electricity. In a WTE facility, solid waste � is burned at extremely high temperatures �, heating water, which turns to steam. The steam turns a turbine �, which powers a generator to create electricity. In an incinerator outfitted with pollution-control technology, toxic gases produced by combustion are mitigated chemically by a scrubber �, and airborne particulate matter is filtered physically in a baghouse � before air is emitted from the stack �. Ash remaining from the combustion process is disposed of � in a landfill.

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be collected, processed, and used in the same way as natural gas (pp. 329–330). Today hundreds of landfills are collecting landfill gas and selling it for energy. At Fresh Kills, collection wells pull landfill gas upward through a network of pipes by vacuum pressure. Landfill gas collected from Fresh Kills is sold by the city for $11 million per year and provides energy for 22,000 Staten Island homes.

Reducing waste is our best option Reducing the amount of material entering the waste stream avoids costs of disposal and recycling, helps conserve re- sources, minimizes pollution, and can save consumers and businesses money. Recall that diminishing waste generation in this way is known as source reduction. One means of source reduction is to lessen the materials used to package goods. Packaging serves worthwhile purposes—preserving fresh- ness, preventing breakage, protecting against tampering, and providing information—but much packaging is extrane- ous. Consumers can give manufacturers incentive to reduce packaging by choosing minimally packaged goods, buying unwrapped fruit and vegetables, and buying food in bulk. Manufacturers can switch to packaging that is more recy- clable. Manufacturers can also reduce the size or weight of goods and materials, as they already have with many items, such as aluminum cans, plastic soft drink bottles, and per- sonal computers. Finally, consumer choice can motivate manufacturers to create goods that last longer.

Some governments have recently taken aim at a major source of waste and litter—plastic grocery bags. These light- weight polyethylene bags can persist for centuries in the environment, choking and entangling wildlife and littering the landscape—yet Americans discard 100 billion of them each year. A number of major cities and over 20 nations have now enacted bans or limits on their use. In 2007, San Francisco became the first U.S. city to ban nonbiodegradable plastic bags. The city’s action saves 14,000 bags every day. Financial incentives are also effective. When Ireland began taxing these bags, their use dropped 90%. The Ikea company began charging for them and saw similar drops in usage. Increasing numbers of stores now give discounts if you bring your own reusable bags.

Reuse is a main strategy to reduce waste To reduce waste, you can save items to use again or substi- tute disposable goods with durable ones. Habits as simple as bringing your own coffee cup to coffee shops or bring- ing sturdy reusable cloth bags to the grocery store can, over time, have substantial impact. You can also donate unwanted items and shop for used items yourself at yard sales and resale centers. Over 6,000 reuse centers exist in the United States, including stores run by organizations that resell donated items, such as Goodwill Industries and the Salvation Army. TABLE 17.1 presents a sampling of actions we all can take to reduce the waste we generate.

Composting recovers organic waste Composting is the conversion of organic waste into mulch or humus (p. 138) through natural decomposition. People place food and yard waste in compost piles, underground pits, or

specially constructed containers. As wastes are added, heat from microbial action builds in the interior, and decomposi- tion proceeds. Banana peels, coffee grounds, grass clippings, autumn leaves, and other organic items can be converted into rich, high-quality compost through the actions of earth- worms, bacteria, soil mites, sow bugs, and other detritivores and decomposers (p. 68). The compost is then used to enrich soil. Home composting is a prime example of how we can live more sustainably by mimicking natural cycles and incorpo- rating them into our daily lives.

Municipal composting programs—3,000 across the United States at last count—divert yard debris from the waste stream to central composting facilities, where it decomposes into mulch that community residents can use for gardens and landscaping. Nearly half of U.S. states now ban yard waste from the municipal waste stream, helping to accelerate the drive toward composting. Composting reduces landfill waste, enhances soil biodiversity, helps soil to resist erosion, makes for healthier plants and more pleasing gardens, and reduces the need for chemical fertilizers.

Recycling consists of three steps Recycling, too, offers many benefits. Recycling involves col- lecting used items and breaking them down so that their materials can be reprocessed to manufacture new items. The recycling loop includes three basic steps (FIGURE 17.8). The first step is collecting and processing used goods and materials.

Communities may designate locations where residents can drop off recyclables or receive money for them. Many of

TABLE 17.1 Some Everyday Things You Can Do to Reduce and Reuse

▶ Donate used items to charity. ▶ Reuse boxes, paper, plastic wrap, plastic containers,

aluminum foil, bags, wrapping paper, fabric, packing material, etc.

▶ Rent or borrow items instead of buying them, when possible . . . and lend your items to friends.

▶ Buy groceries in bulk. ▶ Decline bags at stores when you don’t need them. ▶ Bring reusable cloth bags shopping. ▶ Make double-sided photocopies. ▶ Bring your own coffee cup to coffee shops. ▶ Pay a bit extra for durable, long-lasting, reusable goods

rather than disposable ones. ▶ Buy rechargeable batteries. ▶ Select goods with less packaging. ▶ Compost kitchen and yard wastes in a compost bin or

worm bin (often available from your community or waste hauler).

▶ Buy clothing and other items at resale stores and garage sales.

▶ Use cloth napkins and rags rather than paper napkins and towels.

▶ Write to companies to tell them what you think about their packaging and products.

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these have now been replaced by the more convenient option of curbside recycling, in which trucks pick up recyclable items in front of homes, usually in conjunction with municipal trash collection.

Items collected are taken to materials recovery facilities (MRFs), where workers and machines sort items using auto- mated processes including magnetic pulleys, optical sensors, water currents, and air classifiers that separate items by weight and size. The facilities clean the materials, shred them, and prepare them for reprocessing.

Once readied, these materials are used in manufactur- ing new goods. Newspapers and many other paper products use recycled paper, many glass and metal containers are now made from recycled materials, and some plastic containers are of recycled origin. Some benches, bridges, and walkways in city parks are now made from recycled plastics, and glass is sometimes mixed with asphalt (creating “glassphalt”) for pav- ing roads and paths.

If the recycling loop is to function, consumers and busi- nesses must complete the third step in the cycle by purchasing ecolabeled products (p. 109) made from recycled materials. Buying recycled goods provides economic incentive for in- dustries to recycle materials and for new recycling facilities to open or existing ones to expand.

Recycling has grown rapidly Today 9,000 curbside recycling programs serve nearly half of all Americans. These programs, and the 500 MRFs operating today, have sprung up only in the last 25 years. Recycling in the United States has risen from 6.4% of the waste stream in 1960 to 25.2% in 2009 (and 33.8% if you include composting), according to EPA data (FIGURE 17.9).

Recycling rates vary greatly from one product or material type to another—from 7% for plastics to 25% for glass to 62% for paper to 96% for auto batteries. Recycling rates among U.S. states also vary greatly, from 2% to 43%.

Recycling’s growth has been propelled in part by eco- nomic forces as established businesses see opportunities to save money and as entrepreneurs see opportunities to start new businesses. It has also been driven by the desire of mu- nicipalities to reduce waste and by the satisfaction people take in recycling. These latter two forces have driven recycling’s rise even when it has not been financially profitable. In fact, many of the increasingly popular municipal recycling pro- grams are run at an economic loss. The expense required to collect, sort, and process recycled goods is often more than recyclables are worth in the market. Furthermore, the more people recycle, the more glass, paper, and plastic is available to manufacturers for purchase, driving down prices. And trans- porting items to recycling facilities can sometimes involve surprisingly long distances (see THE SCIENCE BEHIND THE STORY, pp. 388–389).

Recycling advocates, however, point out that market prices do not take into account external costs (p. 92)—in particular, the environmental and health impacts of not recy- cling. For instance, it has been estimated that globally, recy- cling saves enough energy to power 6 million households per year. Each year in the United States, recycling and compost- ing together prevent greenhouse gas emissions equal to that of 33 million cars. And recycling aluminum cans saves 95% of the energy required to make the same amount of aluminum from mined virgin bauxite, its source material.

As more manufacturers use recycled products and as more technologies and methods are developed to use recy- cled materials in new ways, markets should continue to ex- pand and new business opportunities should arise. We are just beginning to shift from an economy that moves linearly

1 3 2Consumer purchase of productsmade from recycledmaterials Use of recyclablesby industry to manufacturenew products

Collection and processing of recyclable materials

by municipalities and businesses

FIGURE 17.8  The familiar recycling symbol consists of three arrows to represent the three components of a sustainable recycling strategy: collection and processing of recyclable materials, use of the materials in making new products, and consumer purchase of these products.

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Pe rc

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Total waste recovered

Percent recovered

FIGURE 17.9  Recovery has risen sharply in the United States over the past 50 years. Today over 80 million tons of material is recovered (61 million tons through recycling and 21 million tons through municipal composting), comprising one-third of the waste stream. Data from U.S. Environmental Protection Agency, 2010. Municipal solid waste in the United States: 2009 facts and figures. EPA, Wash-

ington, D.C.

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Tracking Trash

Where does your trash go once you throw it away? Where does your recycling go? How far might it travel, and how much energy does it take to get rid of it? With the help of the latest tracking

technology, we can find out. Research- ers from the SENSEable City Lab at the Massachusetts Institute of Technology (MIT) are affixing tiny sensors to every- day items in our trash and monitoring them to reveal their hidden travels. By documenting what actually happens to trash and to recyclables, they hope to help make the trash removal process more effective and to encourage bet- ter recycling.

The Trash Track project was launched in 2009 in New York City and in Seattle, and is now expanding to other cities. It was inspired by PlaNYC (pp. 411–412), which aims to raise New York City’s recycling rate from 30% to 100% by 2030. Early results were unveiled at public exhibitions put on in New York and Seattle in late 2009.

Here’s how trash-tracking works: Project director Carlo Ratti and as- sociate director Assaf Biderman, both architects at MIT, organize research teams and local volunteers in the target city to affix tiny electronic tags

(first figure) to hundreds of items be- ing thrown away. As each item makes its final journey through the waste stream, its tag calculates its loca- tion every few hours and relays the information via the cell phone network to a central server at the MIT lab. A computer plots the movements atop satellite maps, helping the researchers to visualize and interpret the migration of trash.

Each trash tag calculates its posi- tion by measuring the signal strength from nearby cell phone towers and comparing this to a map of tower locations. Second-generation tags the project is now using are more accurate, as they combine global positioning system (GPS) technology with better- quality cell network triangulation. To extend battery life to two months or more, the tags are programmed to “sleep” when they are motionless and to “wake up” and report their location frequently when they are moving (when they sense new cell towers coming into range).

As an example, a plastic con- tainer of liquid soap was tagged on September 5, 2009, and placed in the trash at 457 Madison Avenue in Manhattan (second figure). Mapping reveals that the truck that picked it up looped through the city’s streets a few times on its route, crossed the Hudson River via the Lincoln Tun- nel, and headed to Rutherford, New Jersey. Here it turned south and continued, and was in transit along the Bellevue Turnpike in Kearny, New Jersey, three days later when the tag’s battery gave out.

Tags used in New York City and Seattle used the cell phone network to calculate their location. Tags now being used in other cities use GPS technology as well.

Where will it go?

from raw materials to products to waste, to a more sustainable economy that moves circularly using waste products as raw materials for new manufacturing. The steps we have taken in recycling so far are central to this transition.

Costs of Recycling and Not Recycling Should recycling programs be subsidized by governments even if they are run at an economic loss? What types of external costs—costs not

reflected in market prices—do you think would be involved in not recycling, say, aluminum cans? Do you feel these costs justify sponsoring recycling programs even when they are not financially self-supporting? Why or why not?

We can recycle material from landfills With improved technology for sorting rubbish and recycla- bles, businesses and entrepreneurs are weighing the economic benefits and costs of rummaging through landfills to salvage materials of value that can be recycled. Metals like steel, alu- minum, and copper are abundant enough in some landfills to make such salvage operations profitable when market prices for the metals are high enough. For instance, Americans throw out so many aluminum cans that at 2010 prices for alu- minum, the nation buries $1.8 billion of this metal in land- fills each year. If we could retrieve all the aluminum from U.S. landfills, it would exceed the amount the world produces from a year’s worth of mining ore. Besides metals, landfills also offer organic waste that can be mined and sold as pre- mium compost. And old landfill waste can be incinerated

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As of 2011, the project had posted mapped data of all its Seattle items on- line, and was preparing to do the same for its New York items.

The results from Seattle reveal some expected patterns but also some odd surprises. Of the 760 trash items tagged, about 200 ended up at the city’s Allied Waste Recycling Center and Transfer Station after brief jour- neys. Smaller numbers were trans- ported to other city or regional landfills and recycling centers. But some items followed surprisingly circuitous routes, being transferred from one waste center to another, or back and forth between cities. Some ended up in seemingly random places, perhaps having fallen off a garbage truck along a roadside.

A few items made very long jour- neys. Two printer cartridges were driven down Interstate 5 to California’s border with Mexico, perhaps to be disassem- bled at a maquiladora (pp. 89, 106) along the border. Two cell phones were transported halfway across the country to Dallas (one flown directly and one making apparent stops at three other cities). A compact fluorescent bulb went to St. Louis after traveling to Portland, Oregon, and back to Seattle. Chicago received a coffee cup that appar- ently made its way east on the nation’s interstates. Shipments of batteries were flown 1,500 miles to Minneapolis, 2,500 miles to Pittsburgh, and 2,600 miles to Atlanta.

The longest-traveling piece of trash was a cell phone that was trans- ported over 3,000 miles to the other

corner of the United States, ending up near Ocala, Florida.

Why did these trash items migrate so far? How much gasoline was used to transport them? When we move items such great distances to dispose of them or recycle their parts, does that reflect efficiency from an economy of

scale—or does it indicate an excessive waste of resources? Do we need more recycling and disassembly facilities nearer to each major city? Researchers and waste managers hope to use data from the Trash Track project to address such questions and improve the way we handle waste.

Last seen at 786-798 Bellevue Turnpike, Kearny, NJ

Traveled 18.3 miles

Disposed at 457 Madison Ave., New York, NY

Sep 8th, 2009, 07:26 AM

Sep 5th, 2009, 09:02 AM

Sep 5th, 2009, 07:22 AM

Sep 5th, 2009, 07:18 AM

Sep 5th, 2009, 05:19 AM

Sep 5th, 2009, 05:02 AM

Sep 5th, 2009, 04:34 AM Sep 5th, 2009, 04:21 AM

Sep 5th, 2009, 04:13 AM

Green Point

New York

Union City

Secaucus

Hoboken

North Arlington

Lyndhurst

Rutherford

Kearny

senseable city lab

East Rutherford

Ridgefield

Palisades Park

Fort Lee

Leonia

Ridgefield Park

Little Ferry

Teterboro

North Bergen

Edgewater

Plastic Container of Liquid Soap

A plastic container of liquid soap put out with the trash on Madison Avenue in New York City looped through midtown Manhattan, crossed the Hudson River, and was last detected traveling down the Bellevue Turnpike in New Jersey.

in newer, cleaner-burning WTE facilities to produce energy. Some companies are even looking into gaining carbon cred- its (p. 322) by harvesting methane leaking from huge open dumps in developing nations in Asia and Africa.

Such approaches are being tried in places from New York to Israel to Sweden to Singapore, and can be profitable when market prices are high enough. The costs of mining landfills and meeting regulatory requirements while commodity pric- es change unpredictably have meant that investing in landfill mining has been risky so far. This could change in the future, though, if prices rise and technologies improve.

Financial incentives help address waste Waste managers offer consumers economic incentives to reduce the waste stream. In “pay-as-you-throw” garbage

collection programs, municipalities charge residents for home trash pickup according to the amount of trash they put out. The less waste the household generates, the less the resident has to pay. Over 7,000 such programs operate in the United States, serving more than one of every four communities.

Bottle bills represent another approach that hinges on financial incentive. In the 11 U.S. states and 17 nations that have these laws, consumers pay a deposit on bottles or cans upon purchase—generally 5 cents per container—and then receive a refund when they return them to stores after use. Where these laws have been enacted, they have proved effec- tive and popular. U.S. states with bottle bills report that their beverage container litter has decreased by 69–84%, their total litter has decreased by 30–64%, and their per capita container recycling rates have risen 2.6-fold. Beverage container recy-

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cling rates for states with bottle bills are 2.5 times higher than for states without them. As of 2011, five of the bottle bill states were seeking to expand their programs, and seven other states were considering establishing programs.

One Canadian city showcases reduction and recycling Edmonton, Alberta, has created one of the world’s most ad- vanced waste management programs. Just 40% of the city’s waste stream goes to its sanitary landfill, whereas 15% is re- cycled and an impressive 45% is composted.

When Edmonton’s residents put out their trash, city trucks take it to their new co-composting plant—at the size of eight football fields, the largest in North America. The bulk of the waste is mixed with dried sewage sludge for one to two days in immense rotating drums. This mixture travels on a conveyor to a screen that removes nonbiodegradable items. It is aerated for several weeks in the largest stainless steel building in North America (FIGURE 17.10). The mix is then passed through a finer screen and is left outside for four to six months. The resulting compost—80,000 tons annually—is made available to area farmers and residents. The facility even filters the air it emits, to eliminate odors.

Edmonton’s program includes a state-of-the-art MRF that handles 30,000–40,000 tons of waste annually, a leach- ate treatment plant, a research center, public education pro- grams, and a wetland and landfill revegetation program. In addition, 100 pipes collect enough landfill gas to power 4,600 homes, bringing thousands of dollars to the city and helping power the new waste management center. Five area businesses reprocess the city’s recycled items. Newsprint and magazines are turned into new newsprint and cellulose insulation, and cardboard and paper are converted into building paper and shingles. Household metal is made into rebar and blades for tractors and graders, and recycled glass is used for reflective paint and signs.

Edmonton has just built a new integrated process- ing and transfer facility to handle both compostable and recyclable waste from homes and businesses, and the city will soon complete a biofuels facility to create ethanol (pp. 359–360) from waste that cannot be recycled or com- posted. With these new facilities, Edmonton hopes to achieve 90% recovery by 2013.

INDUSTRIAL SOLID WASTE In the United States, industrial solid waste is defined as solid waste that is considered neither municipal solid waste nor hazardous waste under the Resource Conservation and Recovery Act. This includes waste from factories, mining activities, agriculture, petroleum extraction, and more. Each year, U.S. industry generates about 7.6 billion tons of waste, according to the EPA, about 97% of which is wastewater. Thus, very roughly, 230 million tons of solid waste is gener- ated by 60,000 facilities each year—an amount about equal to that of municipal solid waste.

Regulation and economics influence industrial waste generation Most methods and strategies of waste disposal, reduction, and recycling by industry are similar to those for munici- pal solid waste. Businesses that dispose of their own waste on site must design and manage their landfills in ways that meet state, local, or tribal guidelines. Other businesses pay to have their waste disposed of at municipal disposal sites. Whereas the federal government regulates municipal solid waste, state or local governments regulate industrial solid waste (with federal guidance). Regulation varies greatly from place to place, but in most cases, state and local reg- ulation of industrial solid waste is less strict than federal regulation of municipal solid waste. In many areas, indus- tries are not required to have permits, install landfill liners or leachate collection systems, or monitor groundwater for contamination.

The amount of waste generated by a manufacturing proc- ess is a good measure of its efficiency; the less waste produced per unit or volume of product, the more efficient that process is, from a physical standpoint. However, physical efficiency is not always reflected in economic efficiency. Often it is cheap- er for industry to manufacture products or perform services quickly but messily. That is, it can be cheaper to generate waste than to avoid generating waste. In such cases, economic efficiency is maximized, but physical efficiency is not. Because our market system rewards only economic efficiency, all too often industry lacks financial incentive to achieve physical ef- ficiency. The frequent mismatch between these two types of efficiency is a major reason why the output of industrial waste is so great.

Rising costs of waste disposal, however, enhance the financial incentive to decrease waste. Once either govern- ment or the market makes the physically efficient use of raw materials also economically efficient, businesses gain financial incentives to reduce their waste.

FIGURE 17.10  Edmonton, Alberta, boasts one of North America’s most successful waste management programs. Inside the aeration building, which is the size of 14 professional hockey rinks, mixtures of solid waste and sewage sludge are exposed to oxygen and composted for 14–21 days.

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Industrial ecology seeks to make industry more sustainable To reduce waste, growing numbers of industries today are experimenting with industrial ecology. A holistic approach that integrates principles from engineering, chemistry, ecol- ogy, and economics, industrial ecology seeks to redesign industrial systems to reduce resource inputs and to maxi- mize both physical and economic efficiency. Industrial ecologists would reshape industry so that nearly everything produced in a manufacturing process is used, either within that process or in a different one. The larger idea behind industrial ecology is that industrial systems should func- tion more like ecological systems, in which organisms use almost everything that is produced. This principle brings industry closer to the ideal of ecological economists, in which economies function in a circular fashion rather than a linear one (p. 93).

Industrial ecologists pursue their goals in several main ways:

▶ They examine the entire life cycle of a given product— from its origins in raw materials, through its manufactur- ing, to its use, and finally its disposal—and look for ways to make the process more efficient. This strategy is called life-cycle analysis.

▶ They try to identify how waste products from one manu- facturing process might be used as raw materials for an- other one. For instance, used plastic beverage containers

are not refilled because of the potential for contamination, but they can be shredded and reprocessed to make other plastic items, such as benches, tables, and decks.

▶ They examine industrial processes with an eye toward eliminating environmentally harmful products and materials.

▶ They study the f low of materials through industrial systems to look for ways to create products that are more durable, recyclable, or reusable.

Attentive businesses are taking advantage of the in- sights of industrial ecology to save money while reducing waste. The Swiss Zero Emissions Research and Initiatives (ZERI) Foundation sponsors dozens of innovative projects worldwide that attempt to create goods and services without generating waste. One example involves breweries, current- ly being pursued in Canada, Sweden, Japan, and Namibia (FIGURE 17.11).

Few businesses have taken industrial ecology to heart as much as the carpet tile company Interface, which founder Ray Anderson set on the road to sustainability over a decade ago. Interface asks customers to return used tiles for recycling and for reuse as backing for new carpet. It modified its tile design and its production methods to reduce waste. It adapted its boilers to use landfill gas for its energy needs. Through such steps, Anderson’s company cut its waste generation by 80%, its fossil fuel use by 45%, and its water use by 70%—all while saving $30 million per year, holding prices steady for its customers, and raising profits by 49%.

(a) Traditional brewery process

(b) ZERI brewery process

Grain Water

Bread

Spent substrate

Shallow algae ponds

Fish pond

Beer

Substrate for mushrooms

Pigs

Waste

Bio-gas

Digester

Spent grain

Waste water

Grain Water

Spent grain

Waste water

Animal feed

Beer

FIGURE 17.11  Traditional breweries (a) produce only beer while generating much waste, some of which goes toward animal feed. ZERI-sponsored breweries (b) use their waste grain to make bread and to farm mushrooms. Waste from the mushroom farming, along with brewery wastewater, goes to feed pigs. The pigs’ waste is digested in containers that capture natural gas and collect nutrients used to nourish algae for growing fish in fish farms. The brewer derives income from bread, mushrooms, pigs, gas, and fish, as well as beer.

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HAZARDOUS WASTE Hazardous wastes are diverse in their chemical composi- tion and may be liquid, solid, or gaseous. By EPA definition, hazardous waste is waste that is either:

▶ Ignitable: Likely to catch fire (for example, natural gas or alcohol)

▶ Corrosive: Apt to corrode metals in storage tanks or equipment

▶ Reactive: Chemically unstable and readily able to react with other compounds, often explosively or by producing noxious fumes

▶ Toxic: Harmful to human health when inhaled, ingested, or touched

Hazardous wastes are diverse Industry, mining, households, small businesses, agriculture, utilities, and building demolition all create hazardous waste. Industry produces the largest amounts of hazardous waste, but in most developed nations industrial waste generation and disposal is highly regulated. This regulation has limited the amount of hazardous waste entering the environment from industrial activities. As a result, households now are the largest source of unregulated hazardous waste.

Household hazardous waste includes a wide range of items, such as paints, batteries, oils, solvents, cleaning agents, lubricants, and pesticides. U.S. citizens generate 1.6 million tons of household hazardous waste annually, and the average home contains close to 45 kg (100 lb) of it in sheds, basements, closets, and garages.

Many hazardous substances become less hazardous over time as they degrade, but some show especially persistent ef- fects. Radioactive substances are an example, and the disposal of radioactive waste poses a serious dilemma (pp. 349–350). Other types of persistent hazardous substances include or- ganic compounds and heavy metals.

Organic compounds and heavy metals can be hazardous In our day-to-day lives, we rely on the capacity of synthetic organic compounds and petroleum-derived compounds to resist bacterial, fungal, and insect activity. Plastic contain- ers, rubber tires, pesticides, solvents, and wood preserva- tives are useful to us precisely because they resist decom- position. We use these substances to protect our buildings from decay, kill pests that attack crops, and keep stored goods intact. However, these compounds’ capacity to resist decay is a double-edged sword, for it also makes them per- sistent pollutants. Many synthetic organic compounds are toxic because they are readily absorbed through the skin and can act as mutagens, carcinogens, teratogens, and en- docrine disruptors (p. 212).

Heavy metals such as lead, chromium, mercury, arsenic, cadmium, tin, and copper are used widely in industry for wir- ing, electronics, metal plating, metal fabrication, pigments, and dyes. Heavy metals enter the environment when paints,

electronic devices, batteries, and other materials are disposed of improperly. Lead from fishing weights and hunting ammu- nition continues to accumulate in rivers, lakes, and forests. In older homes, lead from pipes contaminates drinking water, and lead paint remains a problem, especially for infants. Heavy metals that are fat soluble and break down slowly are prone to bioaccumulate and biomagnify (pp. 216–217).

“E-waste” is growing Today’s proliferation of computers, printers, cell phones, handheld devices, TVs, DVD players, fax machines, MP3 players, and other electronic technology has created a sub- stantial new source of waste (see ENVISIONIT, p. 393). These products have short lifetimes before people judge them ob- solete, and most are discarded after only a few years. The amount of this electronic waste—often called e-waste— is growing rapidly, and now comprises 2% of the U.S. solid waste stream. Over 3 billion electronic devices have been sold in the United States since 1980. Of these, half have been dis- posed of, while about 40% are still being used (or reused) and 10% are in storage. American households discard close to 400 million electronic devices per year—two-thirds of them still in working order (FIGURE 17.12A).

Of the electronic items we discard, roughly four of five go to conventional sanitary landfills and incinerators. How- ever, most electronic products contain heavy metals and toxic flame retardants. Recent research suggests that e-waste should instead be treated as hazardous waste, so the EPA and a number of states are now taking steps to do so.

More and more e-waste today is being recycled. Devices are taken apart, and parts and materials are refurbished and reused in new products. As an example of such recycling, the stylish gold, silver, and bronze medals awarded to athletes in the 2010 Winter Olympic Games in Vancouver (FIGURE 17.12B) were made from metals recovered from e-waste! Ac- cording to EPA estimates, however, Americans still recycle

(a) Discarded computer monitors (b) Vancouver Olympic medals

FIGURE 17.12  Discarded electronic items (a) can leach heavy metals and should be considered hazardous waste, researchers say. However, we can recycle this waste and mine it for precious metals. The gold, silver, and bronze medals awarded to athletes at the 2010 Winter Olympic Games in Vancouver (b) were manufactured in part from precious metals recycled from discarded e-waste.

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E n

v isio

n it

➤

Every five minutes, Americans throw away the number of cell phones shown on this page.

The 426,000 cell phones entering the U.S. waste stream daily can leach toxic heavy metals into the environment ...

... or they can be recycled for reuse and for the recovery of valuable metals.

You Can Make a Difference Recycle your old phone with an approved e-waste recycling service.

Donate your phone to a person or a charity that can reuse it.

Think twice before buying yet another new electronic gadget that you don’t really need.

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Once consolidated, the waste is transported for treatment and disposal.

Under the Resource Conservation and Recovery Act, the EPA sets standards by which states manage hazardous waste. RCRA also requires large generators of hazardous waste to obtain permits. Finally, RCRA mandates that hazardous ma- terials be tracked “from cradle to grave.” As hazardous waste is generated, transported, and disposed of, the producer, car- rier, and disposal facility must each report to the EPA the type and amount of material generated; its location, origin, and destination; and the way it is handled.

Because current U.S. law makes disposing of hazardous waste quite costly, irresponsible companies sometimes illegal- ly dump waste, creating health risks for residents and finan- cial headaches for local governments forced to deal with the mess (FIGURE 17.14). Companies from industrialized nations also sometimes dump hazardous waste illegally in developing nations—a major environmental justice issue (p. 15). This oc- curs despite the Basel Convention, an international treaty to prevent this practice.

High costs of disposal, however, have also encouraged conscientious businesses to invest in reducing their hazardous waste. Many biologically hazardous materials can be broken down by incineration at high temperatures in cement kilns. Others can be treated by exposure to bacteria that break down harmful components and synthesize them into new com- pounds. Additionally, various plants have been bred or en- gineered to take up specific contaminants from soil and then break down organic contaminants into safer compounds or concentrate heavy metals in their tissues. The plants are even- tually harvested and disposed of.

We use three disposal methods for hazardous waste We have developed three primary means of hazardous waste disposal: landfills, surface impoundments, and injection

only one-fifth of their e-waste, and so many more items are manufactured each year that the amounts produced and dis- carded are growing faster than the amount recycled.

Besides keeping toxic substances out of our environment, recycling e-waste is beneficial because a number of trace metals used in electronics are globally rare, so they can be lucrative to recover. A typical cell phone contains close to a dollar’s worth of precious metals. Every bit of metal we can recycle from a manufactured item is a bit of metal we don’t need to mine from the ground. Thus, “mining” e-waste for precious metals helps reduce environmental impacts from mining. By one estimate, 1 ton of computer scrap contains more gold than 16 tons of mined ore from a gold mine.

There are serious concerns about the health risks that e- waste recycling may pose to workers doing the disassembly. Wealthy nations ship much of their e-waste to developing countries, where low-income workers disassemble the devices and handle toxic materials with minimal safety regulations. These environmental justice concerns need to be resolved if electronics recycling is to be conducted safely and responsibly.

In many North American cities, used electronics are col- lected by businesses, nonprofit organizations, or municipal services, and are processed for reuse or recycling. So next time you upgrade to a new computer, TV, cell phone, or handheld device, find out what opportunities exist in your area to recy- cle your old ones.

Several steps precede the disposal of hazardous waste Many communities designate sites or special collection days to gather household hazardous waste, or designate facili- ties for the exchange and reuse of substances (FIGURE 17.13).

FIGURE 17.13  Many communities designate collection sites or collection days for household hazardous waste. Here, workers handle waste from an Earth Day collection event near Los Angeles.

FIGURE 17.14  Unscrupulous individuals or businesses some- times dump hazardous waste illegally to avoid disposal costs.

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Contaminated sites are being cleaned up, slowly Many thousands of former military and industrial sites re- main contaminated with hazardous waste in the United States and virtually every other nation on Earth. For most na- tions, dealing with these messes is simply too difficult, time- consuming, and expensive. In 1980, however, the U.S. Con- gress passed the Comprehensive Environmental Response Compensation and Liability Act (CERCLA). This law estab- lished a federal program to clean up U.S. sites polluted with hazardous waste. The EPA administers this cleanup program, called the Superfund. Under EPA auspices, experts identify polluted sites, take action to protect groundwater, and clean up the pollution. Later laws also charged the EPA with clean- ing up brownfields, lands whose reuse or development are complicated by the presence of hazardous materials.

Two well-publicized events spurred creation of the Su- perfund legislation. In Love Canal, a residential neighborhood in Niagara Falls, New York, families were evacuated in 1978– 1980 after toxic chemicals buried by a company and the city in past decades rose to the surface, contaminating homes and an elementary school. In Missouri, the entire town of Times Beach was evacuated and its buildings demolished after being contaminated in the 1970s by dioxin (p. 213) from waste oil sprayed on its roads.

Once a Superfund site is identified, EPA scientists evalu- ate how close the site is to human habitation, whether wastes are currently confined or likely to spread, and whether the site threatens drinking water supplies. Sites that appear harmful are placed on the National Priorities List, ranked according to the level of risk to human health that they pose. Cleanup pro- ceeds as funds are available. Throughout the process, the EPA is required to hold public hearings to inform area residents of its findings and to receive feedback.

The objective of CERCLA was to charge the polluting parties for cleanup of their sites, according to the polluter- pays principle (p. 107). For many sites, however, the responsi- ble parties cannot be found or held liable, and in such cases— roughly 30% so far—cleanups have been covered by taxpayers’ funds and from a trust fund established by a federal tax on industries producing petroleum and chemical raw materials. However, Congress let the tax expire and the trust fund went bankrupt in 2004, so taxpayers are now shouldering the entire burden of the program. As funding dwindles and the remain- ing cleanup jobs become more expensive, fewer cleanups are being completed.

As of 2011, 1,288 Superfund sites remained on the National Priorities List, and only 349 had been cleaned up or otherwise deleted from the list. The average cleanup has cost over $25 million and has taken 15 years. Many sites are contaminated with chemicals we have no effective way to deal with. In such cases, cleanups aim simply to isolate waste from human contact, either by building trenches and clay or con- crete barriers around a site or by excavating contaminated material and shipping it to a hazardous waste disposal facility. For all these reasons, the current emphasis in the United States and elsewhere is on preventing hazardous waste con- tamination in the first place.

wells. These do nothing to lessen the hazards of the substanc- es, but they help keep the waste isolated from people, wildlife, and ecosystems. Design and construction standards for land- fills that receive hazardous waste are stricter than those for ordinary sanitary landfills. Hazardous waste landfills must have several impervious liners and leachate removal systems and must be located far from aquifers. Dumping of hazardous waste in ordinary landfills has long been a problem. In New York City, Fresh Kills largely managed to keep hazardous waste out, but most of the city’s older landfills were declared to be hazardous sites because of past toxic waste dumping.

Liquid hazardous waste, or waste in dissolved form, may be stored in surface impoundments, shallow depressions lined with plastic and an impervious material, such as clay. The liquid or slurry is placed in the impoundment and allowed to evaporate, leaving a residue of solid hazardous waste on the bottom. This process is repeated and eventually the dry resi- due is removed and transported elsewhere for permanent dis- posal. Impoundments are not ideal. The underlying layer can crack and leak waste. Some material may evaporate or blow into surrounding areas. Rainstorms may cause waste to over- flow and contaminate nearby areas. For these reasons, surface impoundments are used only for temporary storage.

The third method is intended for long-term disposal. In deep-well injection, a well is drilled deep beneath the water table into porous rock, and wastes are injected into it (FIGURE 17.15). The waste is meant to remain deep under- ground, isolated from groundwater and human contact. However, wells can corrode and can leak wastes into soil, con- taminating aquifers. Roughly 34 billion L (9 billion gal) of haz- ardous waste are placed in U.S. injection wells each year.

Injection well

Injected hazardous waste

Unconfined aquifer

Impervious soil

Porous rock

Confined aquifer

FIGURE 17.15  Liquid hazardous waste may be pumped deep underground by deep-well injection. The well must be drilled below any aquifers, into porous rock separated by impervious clay. The technique is expensive, and waste may leak from the well shaft into groundwater.

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6. What are the three elements of a sustainable process of recycling?

7. In your own words, describe the goals of industrial ecology.

8. What four criteria are used to define hazardous waste? Why are heavy metals and synthetic organic compounds particularly hazardous?

9. What are the largest sources of hazardous waste? Describe three ways to dispose of hazardous waste.

10. What is the Superfund program? How does it work?

1. Describe five major methods of managing waste. Why do we practice waste management?

2. Why have some people labeled the United States “the throwaway society”? How much solid waste do Ameri- cans generate, and how does this amount compare to that of people from other countries?

3. Name several guidelines by which sanitary landfills are regulated. Describe three problems with landfills.

4. Describe the process of incineration or combustion. What happens to the resulting ash? What is one drawback of incineration?

5. What is composting, and how does it help reduce input to the waste stream?

� CONCLUSION We have made great strides in addressing our waste prob- lems. Modern methods of waste management are far safer for people and gentler on the environment than past prac- tices of open dumping and open burning. Recycling and composting efforts are advancing steadily, and Americans now divert one-third of all solid waste away from disposal. The continuing growth of recycling, driven by market forc- es, public policy, and consumer behavior, shows potential to further alleviate our waste problems.

Despite these advances, our prodigious consumption habits have created more waste than ever before. Our waste management efforts are marked by a number of difficult chal- lenges, including the cleanup of Superfund sites, safe disposal of hazardous and radioactive waste, and frequent local opposi- tion to disposal sites. These dilemmas make clear that the best solution is to reduce our generation of waste. Finding ways to reduce, reuse, and efficiently recycle the materials and goods that we use stands as a key challenge for our new century.

T E S T I N G Y O U R C O M P R E H E N S I O N

S E E K I N G S O L U T I O N S

1. How much waste do you generate? Look into your waste bin at the end of the day, and categorize and measure the waste there. List all other waste you may have generated in other places throughout the day. How much of this waste could you have avoided generating? How much could have been reused or recycled?

2. Some people have criticized current waste management practices as merely moving waste from one medium to another. How might this criticism apply to the methods now in practice? What are some potential solutions?

3. Of the various waste management approaches covered in this chapter, which ones are your community or campus pursuing, and which are they not pursuing? Would you suggest that your community or campus start pursuing any new approaches? If so, which ones, and why?

4. THINK IT THROUGH You are the CEO of a major cor- poration that produces containers for soft drinks and a wide variety of other consumer products. Your company’s

shareholders are asking that you improve the company’s image—while not cutting into profits—by taking steps to reduce waste. What steps would you consider taking?

5. THINK IT THROUGH You are the president of your col- lege or university. Your trustees want you to engage with local businesses and industries in ways that benefit both the school and the community. Your faculty and students want you to make the school a leader in waste reduction and industrial ecology. Consider the industries and busi- nesses in your community and the ways they interact with facilities on your campus. Bearing in mind the principles of industrial ecology, can you think of any novel ways that your school and local businesses might mutually benefit from one another’s services, products, or waste materials? Are there waste products from one business, industry, or campus facility that another might put to good use? Can you design an eco-industrial park that might work on your campus? What steps would you propose to take as president?

C A L C U L A T I N G E C O L O G I C A L F O O T P R I N T S

The 17th biennial “State of Garbage in America” survey documents the ability of U.S. residents to generate prodi- gious amounts of municipal solid waste (MSW). Accord- ing to the survey, on a per capita basis, Missouri residents generate the least MSW (4.49 lb/day), and Hawaii residents

generate the most (15.84 lb/day). The average for the entire country is 7.01 lb MSW per person per day. Calculate the amount of MSW generated in 1 day and in 1 year by each of the groups indicated, at each of the rates shown in the accompanying table.

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Groups generating municipal solid waste

Amount of municipal solid waste generated

U.S. average (7.01 lb/day) Missouri (4.49 lb/day) Hawaii (15.84 lb/day)

Day Year Day Year Day Year

You 7.01 2,559

Your class

Your state

United States

World Data from van Haaren, R., et al., 2010. The state of garbage in America. BioCycle 51(10): 16–23.

1. Suppose your town of 50,000 people has just approved construction of a landfill nearby. Estimates are that it will accommodate 1 million tons of MSW. Assuming the landfill is serving only your town, and that your town’s residents generate waste at the U.S. average rate, for how many years will it accept waste before filling up? How much longer would a landfill of the same capacity serve a town of the same size in Missouri?

2. One study has estimated that the average world citizen generates 1.47 pounds of trash per day. How many times more does the average U.S. citizen generate?

3. The same study showed that the average resident of a low-income nation generates 1.17 pounds of waste per day and the average resident of a high-income nation generates 2.64 pounds per day. Why do you think U.S. residents generate so much more MSW than people in other “high-income” countries, when standards of living in those countries are comparable?

Go to www.masteringenvironmentalscience.com for homework assignments, practice quizzes, Pearson eText, and more.

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