Peak Oil

Botkin, Daniel B. Environmental Science: Earth as a Living Planet, 9th Edition. Wiley, 2013-12-23. VitalBook file.

Oil Boom in North Dakota

Until recently, we thought that the oil resources of the world, and particularly those of North America, were becoming harder to find and that we were searching more and more for less and less oil. All that has changed in the past decade with the realization that oil in deep shale rock is becoming available and those resources are many times more abundant than what we previously thought.1 For example, compared to an evaluation in 1995, the U.S. Geological Survey now estimates that there is at least a 25-fold increase in the amount of oil that can be recovered in North Dakota in what is called the Bakken Play (oil people label a discovery and re- covery event a play). Many wells are being drilled in North Dakota, and this is having a significant impact on the environment of the state, in particular on small agricultural towns (Figure 15.1).

The economic recession that began in the United States in 2008 has taken a tremendous toll on most of the states; budgets are strapped, and many people are un- able to find employment. That is not the case in North Dakota, where the unemployment rate in late 2012 was below 4% and the state budget had a significant surplus. This is due to the discovery and exploitation of oil that is spread deep in the ground over a very wide area in the tight shale rock of the Bakken formation. North Dakota’s

population did not grow significantly in 80 years. Now the western part of the state is experiencing boom condi- tions, and more jobs (most of them high-paying) are avail- able than can be filled.

Counties in western North Dakota with popula- tions of about 20,000 have grown by that amount in a very short time, and as a result local environments are being stressed at all levels. Often, roads are inad- equate for the increased traffic, wastewater treatment becomes a problem, and sewage treatment facilities are overwhelmed. Schools and other institutions and sup- port facilities are also experiencing stress. At any one time about 200 new wells are being drilled. and each of these is reported to produce more than 100 jobs. This amounts to employment for about 25,000 people and several thousand more support jobs related to the oil industry. Recovery of the oil requires hydrologic frac- turing, which is more expensive than the process used to extract oil in other regions where more traditional oil fields are found.

People in North Dakota are seeing their farming and idyllic, pre-boom lives changing quickly. Some small towns are growing so rapidly that they can’t even keep track of the increase in population and the amount of drilling in the Bakken oil fields. This has occurred because the size of the area underlain by oil is vast, covering about one-third of North Dakota and into Montana and Canada. The implications of all the newfound oil depos- its in North Dakota are profound. At a time when environmentalists are striving to move the United States to energy self-sufficiency through renewable energy sources, with natural gas as a transition fuel, there is con- cern that exploitation of vast amounts of new oil will exacerbate the carbon loading in the environment, as well as contribute to well-known environmental problems associ- ated with fossil fuels. In this chapter, we will examine some of the consequences of addi- tional exploitation, recovery, and use of fossil fuels. In subsequent chapters, we will discuss alternative energy and nuclear power.

Fossil fuels are forms of stored solar energy. Plants are solar energy collectors because they can convert solar energy to chemical energy through photosynthesis (see Chapter 7). The fossil fuels used today were created from incomplete biological decomposition of dead organic matter (mostly land and marine plants). Buried organic matter that was not completely oxidized was converted by chemical reac- tions over hundreds of millions of years to oil, natural gas, and coal. Biological and geologic processes in various parts of the geologic cycle produce the sedimentary rocks in which we find these fossil fuels.2,3

The fossil fuels—crude oil, natural gas, and coal—are our primary energy sources; they provide approximately 87% of the energy consumed worldwide. World energy consumption grew about 2.5% in 2011. The largest in- crease was in China due to burning more coal. In 2011 China mined and burned about 50% of the total coal used in the world. In the United States, consumption of fos- sil fuels has remained nearly constant since 2010, even as the U.S. population increased by about 3 million people.1 There is significant variability in the use of fossil fuels. China uses a lot of coal, and the Middle East relies on oil and gas to provide nearly all of its energy. The energy use per person also varies significantly. The United States, with 314 million people, uses about the same amount of energy as China with its population of 1.3 billion. Thus the U.S. energy use per person is more than four times that of China.

15.2 Oil

Most geologists accept the hypothesis that crude oil and natural gas are derived from organic materials (mostly plants) that were buried with marine or lake sediments in what are known as depositional basins. Oil is found primar- ily along geologically young tectonic belts at plate boundar- ies, where large depositional basins are likely to occur (see Chapter 7). However, there are exceptions, such as in Texas, the Gulf of Mexico, North Dakota, and the North Sea, where oil has been discovered in depositional basins (some geologically very old) far from active plate boundaries.

The source material, or source rock, for oil and gas is fine- grained (less than 1/16 mm, or 0.0025 in., in diameter), organic-rich sediment buried to a depth of at least 500 m (1,640 ft), where it is subjected to increased heat and pres- sure. The elevated temperature and pressure initiate the chemical transformation of the sediment’s organic material into oil and gas.

Conventional and Continuous Oil and Gas Resources

When we speak of the oil and gas resources of a particular field, area, or region, we are talking about the total amount of oil and gas present in the rocks. Resources now or can in

the future be extracted at a profit. Oil and gas reserves are that portion of the resource that is identified and is currently available to be legally extracted at a profit. The distinction between resources and reserves is based on geologic, legal, and economic factors. As the price of oil increases, more of the resource may be considered a reserve. New technology to extract oil and gas that previously was not available under the old technology may increase both the resource and re- serves. A personal analogy may help illustrate this idea: Your reserves are the money you have in your bank account while your resource is the potential money you can earn in the future. Your resources cannot pay your bills today.

Conventional oil resources are located in discrete oil fields where the oil and gas are trapped geologically. The pressure of deep burial compresses the sediment; this, along with the elevated temperature in the source rock, initiates the upward migration of the oil, which is relative- ly light, to a lower-pressure environment (known as the reservoir rock). The reservoir rock is coarser-grained and relatively porous (it has more and larger spaces between the grains). Sandstone and porous limestone, which have a relatively high proportion (about 30%) of empty space in which to store oil, are common reservoir rocks.

As already mentioned, oil is light; if the upward mo- bility of oil and gas is not blocked, they will escape to the atmosphere. This explains why oil in conventional re- sources is not generally found in geologically old rocks. Oil and gas in rocks older than about 0.5 billion years have had ample time to migrate to the surface, where they have either vaporized or eroded away.3

The oil fields from which we extract conventional oil resources are places where the natural upward migration of the oil to the surface is interrupted or blocked by what is known as a trap (Figure 15.2). The rock that helps form the trap, known as the cap rock (seal) is usually a very fine- grained sedimentary rock, such as shale, composed of silt and clay-sized particles. A favorable rock structure, such as an anticline (arch-shaped fold) or a fault (fracture in the rock along which displacement has occurred), is necessary to form traps, as shown in Figure 15.2. The important concept is that the combination of favorable rock struc- ture and the presence of a cap rock allow deposits of oil to accumulate in the geologic environment, where they are then discovered and extracted.3

Continuous Oil Resources

Continuous oil resources, as compared to conventional resources, are regional in extent, occurring in broad geologic basins—the Bakken formation in North Dakota, for example (see the Case Study at the beginning of this chapter and Figure 15.3). These have no obvious seals or traps, have a large resource volume, and a low recovery factor. When favorable geologic conditions converge, “sweet spots” are identified in the continuous resource where economic extraction of oil is favorable. The rocks in which continuous oil resources are found are usually fine-grained shales

(tight shale) where extraction is expensive and difficult. Other types of continuous oil deposits, other than tight shale, include oil shale and tar sands.

Tar Sands and Shale Oil

Oil shale and tar sands play a minor role in today’s mix of available fossil fuels, but they may be more significant in the future, when traditional oil from wells becomes scarce.

Tar sands are sedimentary rocks or sands impregnated with tar oil, asphalt, or bitumen. Petroleum cannot be recovered from tar sands by pumping wells or other usual commercial methods because the oil is too viscous (thick) to flow easily. Oil in tar sands is recovered by first mining the sands—which are very difficult to remove—and then washing the oil out with hot water. It takes about two tons of tar sand to produce one barrel of oil.

Some 75% of the world’s known tar sand deposits are in the Athabasca Tar Sands in the province of Alberta, Canada. About 19% of U.S. oil imports come from Canada, and about one-half of this is from tar sands.4 The total Canadian resource that lies beneath approximately 78,000 km2 (30,116 mi2) of land is about 300 billion barrels. About half of this (173 billion barrels) can be economically recovered today.4 Production of the Athabasca Tar Sands is currently about 1.6 million barrels of synthetic crude oil per day. Production will likely increase to about 3 million barrels per day in the next decade.

In Alberta, tar sand is mined in a large open-pit mine (Figure 15.4). The mining process is complicated by the fragile native vegetation—a water-saturated mat known as a muskeg swamp, a kind of wetland that is difficult to remove except when frozen. The mining of the tar sands has serious environmental consequences, ranging from a rapid increase in the human population in mining areas to the need to reclaim the land disturbed by the mining. Restoration of this fragile, naturally frozen (permafrost) environment is difficult. There is also a waste-disposal problem because the mined sand material, like the mined oil shale just discussed, has a greater volume than the unmined material. The land surface can be up to 20 m (66 ft) higher after mining than it was originally. Finally, recovery of oil from tar sand, as with any oil development, is an inherently dirty process, and pollution of air, water, and soil is a continual hazard due to spills and other industrial accidents. The Canadian ap- proach requires that following mining the land be returned not to its original use but to some equivalent5use, such as turning what was forestland into grazing land.

Transporting oil from tar sands through pipelines also has potential environmental problems. In 2010, a pipe- line containing heavy oil from Canada’s tar sands ruptured and spilled about 4,000 cu m (1 mil gal) of oil into the Kalamazoo River in Michigan. The heavy oil sank to the riverbed, making cleanup difficult and expensive. The river was closed to the public for nearly two years. About 58 km (36 mi) of the river was heavily impacted as people decided to abandon their homes during the worst of the spill due to toxic odors. The spill is expected to have long-term health effects on people. Some oil remains in the river, even after over $75 million was spent in the cleanup.

Oil shale is a fine-grained sedimentary rock containing organic matter (kerogen). When heated to 500°C (900°F) in a process known as destructive distillation, oil shale yields up to nearly 60 L (14 gal) of oil per ton of shale. If not for the heating process, the oil would remain in the rock. The oil from shale is one of the so-called synfuels (from the words synthetic and fuel), which are liquid or gaseous fuels derived from solid fossil fuels. The best-known sources of oil shale in the United States are found in the Green River formation, which underlies approximately 44,000 km2 (17,000 mi2) of Colorado, Utah, and Wyoming.

Total identified world oil shale resources are estimat- ed to be equivalent to about 3 trillion barrels of oil (more than the total world resource of other oil). However, evaluation of the oil grade and the feasibility of economic recovery with today’s technology is not complete. Oil shale resources in the United States amount to about 2 trillion bbl of oil, or two-thirds of the world total. Of this total, 90%, or 1.8 trillion bbl, is located in the Green River oil shales. The total oil that could be removed from U.S. oil shale deposits is about 100 billion barrels. This exceeds the oil reserves of the Middle East! But extraction is not easy, and environmental impacts would be serious.6,7

The environmental impact of developing oil shale varies with the recovery technique used. Both surface and subsurface mining techniques have been considered. Surface mining is attractive to developers because nearly 90% of the shale oil can be recovered, compared to less than 60% by underground mining. However, direct land and ecosystem destruction, which is difficult to restore, and waste disposal are major problems with either surface mining. Subsurface mining generally has smaller direct land and ecosystem destruction. But both surface and subsurface require that oil shale be processed, or retorted (crushed and heated), at the surface. The volume of waste will exceed the original volume of shale mined by 20–30% because crushed rock has pore spaces and, thus, more volume than the solid rock had. (If you doubt this, pour some concrete into a milk carton, remove it when it hardens, and break it into small pieces with a hammer. Then try to put the pieces back into the carton.) Thus, the mines from which the shale is removed will not be able to accommodate all the waste, and its disposal will become a problem.8

Although it is much more expensive and energy con- suming to extract a barrel of oil from shale than it is to pump it from a well, interest in oil shale was heightened by an oil embargo in 1973 and by fear of continued short- ages of crude oil. In the 1980s through the mid-1990s, however, plenty of cheap conventional oil was available, so oil-shale development was put on the back burner. Today, when it is clear that we will face oil shortages in the future, we are seeing renewed interest in oil shale,7 and it is clear that any steep increases in oil prices will likely heighten this interest. This would result in significant environmen- tal, social, and economic impacts in the oil-shale areas, including rapid urbanization to house a large workforce, construction of industrial facilities, and increased demand on water resources.

Production of Oil

Production wells in a conventional oil field recover oil through both primary and enhanced methods. Primary production involves simply pumping the oil from wells, but this method can recover only about 25% of the petroleum in the reservoir. To increase the amount of oil recovered to about 60%, enhanced methods are used. In enhanced recovery, steam, water, or chemicals, such as carbon dioxide or nitrogen gas, are injected into the oil reservoir to push the oil toward the wells, where it can be more easily recovered by pumping.

Production of oil from continuous oil deposits is more complicated and expensive than production of con- ventional oil. The potential resource that may become re- serves in the future is much greater than 2 trillion barrels. For example, the Bakken formation in North Dakota, ex- tending into Montana and Canada, has a total resource of about 500 billion barrels, but what can be obtained now is thought to be as low as 4 billion barrels (the amount the world uses in about 45 days). Recent estimates suggest that as much as 50%, or about 250 billion barrels, may eventually be produced from the Bakken shale. If that proves to be the case, then oil in the Bakken will be very significant in terms of global oil productivity.1

Next to water, oil is the most abundant fluid in the upper part of the Earth’s crust. Most of the known, proven oil reserves, however, are in a few fields. Proven oil reserves are the part of the total resource that has been identified and can be extracted now at a profit. Of the total reserves, 48% are in the Middle East, 20% in South and Central America, 13% in North America, 8.5% in Europe and Eurasia, 8% in Africa, and 2.5% in Asia-Pacific.9

The total resource of conventional oil always exceeds known reserves; it includes oil that cannot be extracted at a profit and oil that is suspected but not proved to be pres- ent. Several decades ago, the amount of oil that ultimately could be recovered (the total resource) was estimated to be about 1.6 trillion9barrels. Today, that estimate is just over 2 trillion barrels. The increases in proven reserves of oil in the last few decades have primarily been due to discov- eries of conventional oil in the Middle East, Venezuela, Brazil, Kazakhstan, and discoveries of continuous oil in the United States and other areas.

Oil in the 21st Century

A decade ago estimates of proven oil reserves suggested that at present production rates oil and natural gas would last only a few decades.10,11 The important question, how- ever, is not how long oil is likely to last at present and future production rates, but when we will reach peak pro- duction. This consideration is important because, follow- ing peak production, less oil will be available, leading to shortages and price shocks. Until recently, it was thought that a peak in production would likely occur between 2020 and 2050, within the lifetime of many people living today.12 Even those who think peak oil production in the near future is a myth acknowledge that the peak is coming and that we need to be prepared.10 Whichever projections are correct, there is a finite amount of time left in which to adjust to potential changes in lifestyle and economies in a post-petroleum era. We will never entirely run out of crude oil in the sense that at least smaller amounts will remain, though they may not economically be worth ob- taining for large-scale use as fuels. Petroleum in the future will remain an important commodity because it is a pre- cursor to many useful chemicals, including many plastics.

15.3 Natural Gas

Natural gas is a mixture of hydrocarbon gases. The most common gas is methane (CH4), but natural gas also includes propane (C3H8) and butane (C4H10). We have only begun to seriously search for natural gas and to utilize the natural gas resource to its full potential. One reason for the slow start is that natural gas is transported primarily by pipelines, and only in the last few decades have these pipelines been constructed in large numbers. In fact, until recently, natural gas found with petroleum was often simply burned off as waste; in some cases this practice continues.8

New supplies of natural gas are being found in large amounts in the United States and other locations. Op- timistic estimates of the total resource suggest that, at current rates of consumption, the global supply may last more than 100 years. Today, over half of all natural gas produced in the United States is from wells drilled since about 2005.

This possibility has important implications. Natural gas is considered a clean fuel; burning it produces fewer pollutants than does burning oil or coal, so it causes fewer environmental problems than do the other fossil fuels. As a result, it is being considered as a possible transition fuel from other fossil fuels (oil and coal) to alternative energy sources, such as solar power, wind power, and ocean power.

There are several types of natural gas resources, including conventional gas fields often associated with drilling for oil. Another group of natural gas resources are unconventional or what is known as continuous gas resources. These include, in order of abundance and probable future use: shale gas, tight gas, and coalbed methane. The final natural gas resource we will briefly discuss is methane hydrates. Figure 15.6 is a schematic diagram illustrating conventional and continuous natural gas deposits that are being exploited today. U.S. natural gas production of some of these sources is shown in Figure 15.7. As of 2010, tight gas was the dominant supplier of natural gas, with other sources and shale gas not far behind. If we look forward to 2035, it is projected that nearly 50% of the total gas resources that are utilized will come from shale gas. Notice that natural gas from Alaska is a very small percentage of the total gas production, but that there is significant production from offshore and inshore sources that are not associated with oil. By 2035, it is expected that coalbed methane, as well as gas associated with oil fields and other sources that are not associated with oil fields, will be relatively small players, compared to shale gas and tight gas. Whether this expectation materializes will depend on economic factors and how readily shale gas may be obtained from the many potential sources in the United States. The Marcellus shale and the Devonian shale below the Marcellus is only one of 19 other basins being explored for shale gas from Michigan to Texas, and the resource is vast. Should all the different sources become available, the United States will have sufficient natural gas for at least a century. However, resources are not reserves, and projections may change in the World’s top 10 producers of oil in 2000 and 2012. the u.S. is now one of the two top producers.

There is an argument that oil should be saved for other purposes than burning it in our automobiles. Neverthe- less, people of the world today depend on oil for nearly 33% of their energy, and significant shortages will cause major problems.1,9

The world production of oil in 2000 and 2012 and is shown in Figure 15.5. In 2000 U.S. production was about 25% less that the world leader Saudi Arabia. Notice that U.S. production in 2012 is just below Saudi Arabia, with Russia not far behind.1 The U.S. increase in oil production is due in large part to development of continuous oil deposits in places such as North Dakota. Forecasts of energy produc- tion are risky because prices may change due to political and economic factors that are difficult to predict, and potential reserves may not materialize.1 The U.S. may become the worlds top producer of oil in the next decade, but the Middle East Region total production will continue to significantly exceed that of the U.S.and the rest of north America.

What is an appropriate response to the likelihood that oil production will likely decline by the late 21st century? First, we need an improved educational program to in- form or remind people and governments of the potential depletion of crude oil and the consequences of shortages. Presently, many people seem to be in denial. Planning and appropriate action are necessary to avoid military con- frontation (we have already had one oil war), food short- ages (oil is used to make the fertilizers modern agriculture depends on), and social disruption. Before significant oil shortages occur, we need to develop alternative energy sources, such as solar energy and wind power, and perhaps rely more on nuclear energy. This is a proactive response to a potentially serious situation.

the future, depending on a variety of circumstances related to the pricing of natural gas and to the cost of obtaining it, including environmental costs.

Shale Gas

Shale gas is natural gas within tiny openings of shale rock. Shale has a lot of open space between grains, but fluids are held tightly.13 According to the U.S. Geological Survey, Black Devonian shale (Marcellus shale) is over 350 mil- lion years old and buried a kilometer or so beneath north- ern Appalachia. The Marcellus shale resource that may be ultimately recovered is about 13.5 trillion cu m (482 million cu ft) of natural gas (mostly methane). At pres- ent consumption, this resource could supply all U.S. de- mand for natural gas for about 20 years. Of course, there are other sources of shale gas in other parts of the United States. The truth is that we are in the early stage of evaluat- ing the shale gas resource and reserves, and numbers will change as more is known about the geology.

Methane is distributed throughout the black shale as a continuous gas resource found in geologic basins in parts of Ohio, New York, Pennsylvania, Virginia, and Kentucky as well as other areas in the United States (Fig- ure 15.8). Recovery of the methane is costly, because deep wells that turn at depth to a horizontal position are neces- sary to extract the gas. Water and other chemicals are used to fracture the rocks (hydrologic fracturing, sometimes called fracking) to recover the gas. An energy rush is un- derway to develop the recovery of natural gas. Hundreds of gas wells have already been permitted in Pennsylvania alone. There is concern that drilling and hydrologic frac- turing could result in water pollution because the fluids used to fracture the rock must be recovered from wells and disposed of before gas production starts (see A Closer Look 15.1). Yet another concern is that contaminated wa- ter could migrate upward and leak from wells to pollute water supplies. The city of New York is very concerned that drilling might contaminate the water supply in up- state New York.

hydrologic Fracturing to recover Oil and Gas

Vast regions of the United States are underlain by very tight, fine-grained sedimentary rocks, such as shale and sandstone, in geologic basins at depths often of several kilometers. These rocks often contain large amounts of fossil fuels—particularly gas and oil—that is tightly held by the fine grains of the shale and is dif- ficult to extract. In order to obtain these resources, the drilling extends deep and then turns horizontally in the target rocks that contain the oil and gas (Figure 15.9). Large amounts of fluids (sometimes millions of gallons, several thousand cubic meters) are injected under high pressure into a single well as the rock is fractured (sometimes multiple times). The fluids are mostly wa- ter (90%) but contain a wide variety of other chemicals to assist in the hydrologic fracturing and to keep the fractures open and so forth (see Table 15.1). A single well that is fractured several times may use several hundred thousand gallons (several hun- dred cubic meters) of fluid chemicals other than water. Many of these chemicals are known to create potential, if not outright, health risks (some are known to cause cancer) if they are released at the surface and people are exposed to the chemicals. There has also been concern that opening the fractures allows natural gas to seep up above the shale rock formations, perhaps to enter groundwater resources near the surface.

Natural gas migrating up through natural fractures or frac- tures from fracking deep below is probably not happening. How- ever, natural gas sometimes is migrating up, perhaps through old, abandoned wells or failure of the wells that are drilled. Furthermore, the fluids that are brought up are sometimes stored at the surface in lined, open pits where they may leak into the environment or be flooded during high precipitation events, pol- luting rivers and the land. Figure 15.10 shows a drilling site and the associated pit that stores drilling fluids. In several instances, pollution from hydrologic fracturing has been recorded. The Environmental Protection Agency has recently studied this prob- lem and is attempting to minimize potential problems through tighter regulation of open pits at the surface and methods of handling drilling and hydrologic fracturing fluids from the time they are pumped into the ground, returned to the surface, stored in tanks to be reused, or eventually eliminated.a,b There has also been concern that hydrologic fracturing may reactivate old faults and cause small earthquakes. High fluid pressure is known to favor earthquake occurrence. One small earthquake in Okla- homa is cited as an example of a hydrologic fracturing-induced earthquake. Many people who study earthquakes report that the pressures with hydrologic fracturing are not high enough to cause much of a change in regional seismicity or earthquakes in areas that have a low initial hazard. However, when fluids used in hy- drologic fracturing are collected and disposed of in deep injection wells near faults, small earthquakes have occurred. This points to the need to understand the subsurface environment well before injecting fluids down specially designed disposal wells.c

At some locations in Pennsylvania, West Virginia, and other states, people are reporting methane seeping into their ground- water supply, with sufficient amounts of methane to cause fear

of potential fires. Of course, methane has always been found in some areas, and there are many early records of people mention- ing natural gas seeping from deep rock formations. However, there is concern that with the many wells being drilled, some of the casings near the surface of the wells may fail, allowing meth- ane to seep into higher levels and contaminate the groundwater.

A tremendous amount of hydrologic fracturing is taking place in the United States in deep rock formations where oil and gas exist, and that trend is not likely to decrease in the future. Therefore, we need to develop adequate regulations to control recovery of the gas and oil as we move from the boom period into standard operating procedures of obtaining the resource. In the summer of 2012, the U.S. Environmental Protection Agency announced some new regulations aimed at reducing the adverse environmental effects of hydrologic fracturing of gas and oil wells. If the new regulations can be followed responsibly, oil and gas reserves in the United States will likely continue to increase.

Tight Gas

Tight gas is natural gas that is produced from continuous deposits (reservoirs) of dense sandstone or limestone. The gas is originally produced in organic rich sediments and over geologic time has migrated to the reservoir rock. The gas is held tightly (hence the name tight gas). Many gas re- covery wells in tight gas rock reservoirs are drilled horizon- tally at depth and are hydrologically fractured to enhance production (see A Closer Look 15.1). The tight gas resource in the United States is very large and supplies about 25% of all the natural gas produced in the country today.

Coal-bed Methane

The processes responsible for the formation of coal in- clude partial decomposition of plants buried by sedi- ments that slowly convert the organic material to coal. This process also releases a lot of methane (natural gas) that is stored within the coal. The methane is actually stored on the surfaces of the organic matter in the coal, and because coal has many large internal surfaces, the amount of methane for a given volume of rock is about seven times more than could be stored in gas reservoirs associated with petroleum. The estimated amount of coal-bed methane in the United States is more than 20 trillion cu m, of which about 3 trillion cu m could be re- covered economically today with existing technology. At current rates of consumption in the United States, this represents about a five-year supply of methane.15 Coal- bed methane constitutes about 9% of the U.S. natural gas production (see Figure 15.7).

Two areas within the nation’s coalfields that are pro- ducing methane are the Wasatch Plateau in Utah and the Powder River Basin in Wyoming. The Powder River Basin is one of the world’s largest coal basins and is experienc- ing an energy boom. The technology to recover coal-bed methane is a young one, but it is developing quickly. An advantage of coal-bed methane wells is that they only need to be drilled to shallow depths (about 100 m, or a few hundred feet). Drilling can be done with conventional water-well technology, and the cost is about $100,000 per well, compared to several million dollars for an oil well.16

The coal industry promotes the idea that coal-bed methane is a promising energy source that comes at a time when the United States is importing vast amounts of energy and attempting to evaluate a transition from fossil fuels to alternative fuels. However, coal-bed meth- ane presents several serious environmental concerns, in- cluding: (1) disposal of large volumes of water produced

when the methane is recovered and (2) migration of methane, which may contaminate groundwater or mi- grate into residential areas. With water becoming a limit- ing resource, this source of coal may not be as practical as some proponents suggest.

Of particular environmental concern in Wyoming is the safe disposal of salty water that is produced with the methane (the wells bring up a mixture of methane and water that contains dissolved salts from contact with sub- surface rocks). Often, the water is reinjected into the sub- surface, but in some instances the water flows into surface drainages or is placed in evaporation ponds.15

Some of the environmental conflicts that have arisen are between those producing methane from wells and ranchers trying to raise cattle on the same land. Fre- quently, the ranchers do not own the mineral rights, and although energy companies may pay fees for the well, the funds are not sufficient to cover damage resulting from producing the gas. The problem results when the salty water produced is disposed of in nearby streams. When ranchers use the surface water to irrigate crops for cattle, the salt damages the soil, reducing crop pro- ductivity. Although it has been argued that ranching is often a precarious economic venture and that ranchers have in fact been saved by new money from coal-bed methane, many ranchers oppose coal-bed methane pro- duction without an assurance that salty waters will be safely disposed of.

People are also concerned about the sustainability of water resources as vast amounts of water are removed from the groundwater aquifers. In some instances, springs have been reported to have dried up after coal-bed meth- ane extraction in the area.16 In other words, the “mining” of groundwater for coal-bed methane extraction will re- move water that has perhaps taken hundreds of years to accumulate in the subsurface environment.

Another concern is the migration of methane away from the well sites, possibly to nearby urban areas. The problem is that, unlike the foul-smelling variety in homes, methane in its natural state is odorless as well as explosive. For example, in the 1970s an urban area near Gallette, Wyoming, had to be evacuated because methane was mi- grating into homes from nearby coal mines.

Finally, coal-bed methane wells, with their compres- sors and other equipment, have caused people living a few hundred meters away to report serious and distressing noise pollution.16 In sum, coal-bed methane is a tremen- dous source of energy and relatively clean burning, but its extraction must be closely evaluated and studied to mini- mize environmental degradation.

Methane Hydrates

Beneath the seafloor, at depths of about 1,000 m, there exist deposits of methane hydrate, a white, ice-like com- pound made up of molecules of methane gas (CH4), mo- lecular “cages” of frozen water. The methane has formed as a result of microbial digestion of organic matter in the sediments of the seafloor and has become trapped in these ice cages. Methane hydrates in the oceans were discovered over 30 years ago and are widespread in both the Pacific and Atlantic oceans. Methane hydrates are also found on land; the first ones discovered were in permafrost areas of Siberia and North America, where they are known as marsh gas.17

Methane hydrates in the ocean occur where deep, cold seawater provides high pressure and low temperatures. They are not stable at lower pressure and warmer tempera- tures. At a water depth of less than about 500 m, methane hydrates decompose rapidly, freeing methane gas from the ice cages to move up as a flow of methane bubbles (like rising helium balloons) to the surface and the atmosphere.

In 1998, researchers from Russia discovered the release of methane hydrates off the coast of Norway. During the release, scientists documented plumes of methane gas as tall as 500 m being emitted from methane hydrate deposits on the seafloor. It appears that there have been many large emissions of methane from the sea. The physical evidence includes fields of depressions, looking something like bomb craters that pockmark the seafloor near methane hydrate deposits. Some of the craters are as large as 30 m deep and 700 m in diameter, suggesting that they were produced by rapid, if not explosive, eruptions of methane.

Methane hydrates in the marine environment are a potential energy resource with approximately twice as much energy as all the known natural gas, oil, and coal deposits on Earth.16 Methane hydrates are particularly at- tractive to countries such as Japan that rely exclusively on foreign oil and coal for their fossil fuel needs. Unfortu- nately, mining methane hydrates will be a difficult task, at least for the near future. The hydrates tend to be found along the lower parts of the continental slopes, where wa- ter is often deeper than 1 km. The deposits themselves extend into the seafloor sediments another few hundred meters. Drilling rigs have more problems operating safely at these depths, and developing a way to produce the gas and transport it to land will be challenging.

15.4 the environmental effects of Oil and Natural Gas

Recovering, refining, and using oil—and to a lesser extent natural gas—cause well-known, documented environmen- tal problems, such as air and water pollution, acid rain, and global warming. People have benefited in many ways from abundant, inexpensive energy, but at a price to the global environment and human health. The following discussion applies to conventional oil and gas, oil and gas in tight shale, and tight gas. Environmental concerns of oil shale, tar sand, and coal-bed methane were discussed with those resources where they were defined in Sections 15.2 and 15.3.

Recovery

Development of oil and gas fields involves drilling wells on land or beneath the seafloor (Figure 15.11).

Possible environmental impacts on land include the following:

• Use of land to construct pads for wells, pipelines, and storage tanks and to build a network of roads and other production facilities. Forestlands are of particular concern. The state of Pennsylvania has determined that of the 61,000 ha (1,500,000 acres) of state forestland underlain by shale gas deposits, nearly half is currently leased or sold for gas development and the other half is not leased because it is in ecologically sensitive areas.

• Pollution of surface waters and groundwater from: (1) leaks from broken pipes or tanks containing oil or other oil-field chemicals; (2) salty water (brine) brought to the surface in large volumes with the oil; and (3) hy- draulic fracturing concerns (see A Closer Look 15.1). (The brine in salty water brought to the surface is toxic and may be disposed of by evaporation in lined pits, which could leak. Pumping it into the ground is another disposal method, using deep wells outside the oil fields. However, disposal wells may pollute groundwater,)

• Accidental release of air pollutants, such as hydrocar- bons and hydrogen sulfide (a toxic gas).

• Land subsidence (sinking) as oil and gas are withdrawn from shallow conventional oil and gas fields.

• Loss or disruption of and damage to fragile ecosystems, such as wetlands or the marine environment. This is the center of the controversy over the development of petroleum resources in pristine environments such as the U.S. Arctic Ocean offshore of Alaska, where vast conventional oil and gas reserves are thought to exist.18 However, the onshore and offshore Arctic region is a remote and fragile environment with unique fish and wildlife reserves. There also are potential social con- cerns regarding indigenous people who rely on the en- vironment to maintain their way of life. As a result, Arctic oil and gas production remains controversial.

Environmental impacts associated with oil produc- tion in the marine environment include the following:

• Oil seepage into the sea from normal operations or large spills from accidents, such as blowouts or pipe ruptures (Figure 15.12). The very serious oil spill in the Gulf of Mexico (April 20, 2010) began from a blowout when equipment designed to prevent a blowout for this well drilled in very deep water (over 1.5 km, 1 mi) failed to operate properly. The platform was destroyed by a large explosion, and 11 oil workers were killed. By the middle of May, oil started to make landfall in Louisiana and other areas, and fishing was shut down over a large area. The oil spread despite the many and continuing

Oil

Louisiana wetland

A Louisiana wetland after the Deepwater Hori- zon oil spill in the Gulf of Mexico.

efforts (chemical dispersants, skimming, and burning, among others) to deter the oil from spreading. The spill was the largest and potentially most damaging in U.S. history (see A Closer Look 15.2).

• Release of drilling muds (heavy liquids injected into the borehole during drilling to keep the hole open). These contain heavy metals, such as barium, which may be toxic to marine life.

• Aesthetic degradation from the presence of offshore oil-drilling platforms, which some people consider unsightly.

Refining

Refining crude oil and converting it to products also have environmental impacts. At refineries, crude oil is heated so that its components can be separated and collected (this process is called fractional distillation). Other indus- trial processes then make products such as gasoline and heating oil.

Refineries may have accidental spills and slow leaks of gasoline and other products from storage tanks and pipes. Over years of operation, large amounts of liq- uid hydrocarbons may be released, polluting soil and groundwater below the site. Massive groundwater- cleaning projects have been required at several West Coast refineries.

Crude oil and its distilled products are used to make fine oil, a wide variety of plastics, and organic chemicals used by society in huge amounts. The industrial processes involved in producing these chemicals have the potential to release a variety of pollutants into the environment.

Delivery and Use

Some of the most extensive and significant environmen- tal problems associated with oil and gas occur when the fuel is delivered and consumed. Crude oil, as with natural gas, is mostly transported on land in pipelines or across the ocean by tankers; both methods present the danger of oil spills. For example, a bullet from a high-powered rifle punctured the Trans-Alaska Pipeline in 2001, causing a small but damaging oil spill. Strong earthquakes may pose a problem for pipelines in the future, but proper engi- neering can minimize earthquake hazard. The large 2002 Alaskan earthquake ruptured the ground by several meters where it crossed the Trans-Alaska Pipeline. The pipeline’s design prevented damage to the pipeline and to the envi- ronment. Although most effects of oil spills are relatively short-lived (days to years), marine spills have killed thou- sands of seabirds, spoiled beaches for decades (especially beneath the surface of gravel beaches), and caused loss of tourist and fishing revenues.

the Oil Spill in the Gulf of Mexico, 2010

America’s biggest oil spill began on April 20, 2010, about 66 km (41 mi) south of the Louisiana coast in the Gulf of Mexico. Everything about the spill was big, very big (Figure 15.13). It happened on the Deepwater Horizon, a floating, semi-submerged drilling platform with a surface area larger than a football field—121 m (396 ft) long and

78 m (256 ft) wide. Built in 2001 at a cost of $600 million and owned by Transocean, the Deepwater Horizon had previ- ously dug the deepest offshore gas and oil well ever—down 10,685 m (35,055 ft). In February 2010, Transocean began a new job under lease by British Petroleum (BP), drilling in waters 1,500 m (5,000 ft) deep. BP’s plan was to use this platform to drill an exploratory well into the bedrock below to a depth of 5,600 m (18,360 ft)—almost 31⁄2 mi into the rock! Pipes descended from the platform through the seawater to the bedrock below, and then drilling began. The wellhead, which sits atop the seafloor, contained devices to control the drilling, to insert drilling fluids (called muds) into the hole, and to control the upward flow of oil and gas once those deposits were reached.

On April 20, things went wrong. Methane (natural gas) from the oil and gas deposits that were being drilled into from

Mississippi River Delta

the platform broke through the wellhead at the surface far below. It rose rapidly, reaching the platform in a short time, starting a fire there at 9:56 p.m. local time and then causing a major explosion. Eleven of the 126 crew members were killed, and many others were injured; some saved themselves by div- ing off the collapsing rig into the ocean. The fire was big—so big and bright that people in boats who came to help said it was hard to look at and that it melted the paint off the boats (see Figure 15.14).

The Deepwater Horizon burned for 36 hours and then, on April 22, it sank, after which the oil spill began in earnest. At first, the U.S. Coast Guard reported that 8,000 barrels a day were leaking, but it was difficult to determine just how much oil was pouring out thousands of feet below. By July, the best estimate was about 60,000 barrels per day. The oil spread widely; by mid-June 2010, medium to heavy amounts of oil had reached more than 160 km (100 mi) east of the platform’s position (Figure 15.15).a

The total amount of oil spilled by mid-July when the leak was stopped was about 5 million barrels (210 mil gal). At this rate of release, the BP spill equaled the Exxon Valdez oil spill (until then the largest spill in U.S. history) every four and a half days. To put these large numbers in perspective, the average school gymnasium would hold about 1.3 million gallons of oil. Thus, the oil spilled in just the first two months of the BP spill would fill more than 100 school gymnasiums.

How does this compare to other blowouts and oil spills? The largest known blowout on land, which happened in Iran in 1956, involved about 120,000 barrels per day and lasted 3 months before being capped, releasing a total of almost 11 million barrels. A number of other “gushers” in the history of oil drilling released about 100,000 barrels per day.

Any way you look at it, the BP spill was a lot of oil released into the Gulf’s fragile marine and coastal environ- ments. Spilled oil that remains near the water surface moves with currents and winds, some of it ending up on shore- lines, partly covering plants and animals, infiltrating the sediment, and doing other kinds of ecological damage (Figure 15.16). Although most effects of oil spills are relatively short-lived (days to a few years), previous marine spills have killed thousands of seabirds, temporarily spoiled beaches, and caused loss of tourist and fishing revenues. Complicating matters, four species of sea turtles (logger- heads, Kemp’s ridley, leatherback, and green) that lay their eggs along Gulf State coasts were impacted by the oil. By June 25, 2010, 555 turtles had been found within the spill, and 417 of them were dead.a

A large volume of natural gas (methane) had been released with the oil, some dissolved in the oil and some from gas pockets. Eventually, much of the methane in the water was degraded by bacteria, whose increased respira- tion decreases oxygen levels in the water. Scientists study- ing the oxygen content of the deep water near the oil rig found oxygen depletion of 2% to 30% at depths of about 304m (1,000 ft.)

The spill was an economic disaster for BP, the oil industry in general, states along the Gulf Coast, and the people living there. If the oil that was spilled in the first 60 days had been obtained and sold, it would have provided BP with about $500 million (commercial value: 5 million barrels at $100 per barrel). By the end of the spill, BP had admitted that the spill had cost the company $1 billion, and it had agreed to provide the U.S. government with $20 billion to repay those who suffered damage from the spill. Oil drilling from platforms was curtailed after the spill, and oil production dropped (production rebounded in 2012 with improved safety). Commercial fishermen were put out of work because a large area of the Gulf’s waters— from Morgan City west of New Orleans, Louisiana, to well east of Panama City, Florida, and south along the Florida Keys—were closed to fishing: an area approximately 480 km (300 mi) east–west and 480 km (300 mi) north– south. Some closed areas were opened by August 2010. People in tourist areas lost money because vacationers were choosing other locations where they wouldn’t have to con- tend with oil on beaches or perception of an environmental problem. Supporting enterprises for commercial fishing and tourism also lost business. In late 2012, the U.S. Department of Justice brought criminal charges against BP and fined the corporation $4.5 billion. The two highest- ranking supervisors onboard Deepwater Horizon when the explosion occurred were charged with 23 criminal counts, including seaman’s manslaughter. BP admitted guilt of 11counts of manslaughter and agreed to pay the $4.5 fine. Civil cases are now pending against BP that involve many billions of dollars in potential liability .

Will the Gulf recover from the 2010 oil spill? Certainly it will. Scientific studies of previous oil spills show that there is al- ways an immediate (scientists call it an “acute”) effect, killing fish, birds, and marine mammals and damaging vegetation and near- shore algae. Over the long run, the oil decomposes, and much of it becomes food for bacteria or nutrients for algae and plants. However, studies of previous oil spills also show that some oil remains even decades after spills, and, therefore, the effects on people, economics, and the environment that people value and enjoy are, from a human perspective, damaged for a long time.

By late August 2010, it was hard to find much floating oil in the Gulf, and some saltmarsh plants were showing signs of recovery. Recovery may be quicker in the Gulf than in Alaska because the warm water favors biologic decomposition of the oil, the oil is light, and the Gulf is a very large, deep, body of water subject to active surface processes from storm-generated wind and waves.

How did the BP spill happen? As with many major environmental disasters, a series of poor decisions were involved, including a failure to take advantage of the safest and best technology. Before the blowout, workers and others were aware of problems with the well, and they expressed concern about being able to prevent an incident in which oil or natural gas would escape. Indeed, the Deepwater Horizon had problems prior to the blowout and received 18 govern- ment citations for pollution. The BP wellhead had been fitted with a blowout preventer, but not with remote control or acoustically activated triggers for use in an emergency. The blowout preventer malfunctioned shortly after the heavy drilling mud had been withdrawn from the wellhead (the function of the drilling mud is to help keep oil from moving up the well to the surface). This is considered one of the major mistakes because without the mud and with the blowout-preventer malfunction, there was only water pres- sure to keep the oil and gas from escaping. And that was a recipe for disaster.

In addition, the response to the oil spill was inadequate. Rather than being proactive, the response was reactive: Each time something went wrong, there was spur-of-the- moment action. Also lacking was a clear line of authority and responsibility. The drilling was being done offshore by a private corporation, but it had large-scale effects, many of which were on government lands and waters and thus came under government control. Some available technologies that could have been applied were not; others were applied in too limited and tentative a way (Figure 15.17). News reports were rife with speculation by poorly informed people about all sorts of things that might be done, from gathering the oil with hay to blowing up the well with an atomic bomb.

About 6,000 boats were deployed with about 25,000 workers to try to minimize the spread of the spill by collecting it in the sea and on land. Some oil was burned, and chemical dispersants were applied from aircraft as well as at the bottom of the sea where the leak was occurring. These dispersants are chemicals and have environmental impacts themselves. It is known that these chemicals can damage marine ecosystems, but in this situation, some scientists considered dispersants the lesser of two evils. Dispersants were used, but their long-term impact, particularly on the deep-sea bed and in the seawater, is largely unknown. This brings up an important point: The science of the deep-ocean basin has not progressed enough to be able to adequately predict the processes there and how they will interact with the oil and dispersants.a

The Deepwater Horizon was just one of nearly 4,000 other platforms in the Gulf off the coast of the United States. From the perspective of environmental science, what lessons can we take home from the BP oil spill?

First of all, it did not have to happen. Best practices—those that take advantage of the best and safest modern technology, developed from modern science—were not followed. Second, modern industrialized nations use huge amounts of petroleum, and even with widespread movements away from petroleum, the need will not cease quickly. Therefore, it is essential that oil exploration and development make use of the best available technology and science, including the sciences that inform us about the environmental and ecological effects of an oil spill. And third, after decades of concern about offshore oil spills, the technologies to deal with their cleanup remain insufficient. What is needed is an oversight program that includes advance planning, early warning, and rapid and sufficient response. Given the huge amount of money spent on energy within the United States and the importance of energy to our nation’s stan- dard of living, creativity, and productivity, we can no longer deal with such things as oil spills in a haphazard way.

15.5 Coal

Partially decomposed vegetation, when buried in a sedi- mentary environment, may be slowly transformed into the solid, brittle, carbonaceous rock we call coal. This process is shown in Figure 15.18. Coal is by far the world’s most abundant fossil fuel, with a total recoverable resource of about 860 billion metric tons (Figure 15.19). The annual world consumption of coal is about 4 billion metric tons. Therefore there is sufficient coal for about 200 years at the current rate of use.9 There are about 18,500 coal mines in the United States with combined reserves of 237 billion tons; 2011 production was 0.57 billion tons. At present rates of mining, U.S. reserves will last about 400 years. By comparison, China produces over three times as much coal as the United States, which is about one-half of total world production.9,19 If, however, consumption of coal increases in the coming decades, the resource will not last nearly as long.

Coal is classified, depending on its energy and sulfur content, as anthracite, bituminous, subbituminous, or lignite (see Table 15.2). The energy content is greatest in anthracite coal and lowest in lignite coal. The distribu- tion of coal in the contiguous United States is shown in Figure 15.20.

The sulfur content of coal is important because low- sulfur coal emits less sulfur dioxide (SO2) and is therefore more desirable as a fuel for power plants. Most low-sulfur coal in the United States is the relatively low-grade, low- energy lignite and subbituminous coal found west of the Mississippi River. Power plants on the East Coast treat the high-sulfur coal mined in their own region to lower its sul- fur content before, during, or after combustion and, thus, avoid excessive air pollution. Although it is expensive, treating coal to reduce pollution may be more economical than transporting low-sulfur coal from the western states.

Coal Mining and the Environment

In the United States, coal mining has disturbed thousands of square kilometers of land, and only about half this land has been reclaimed. Reclamation is the process of restor- ing and improving disturbed land, often by reforming the surface and replanting vegetation (see Chapter 9). Unre- claimed coal dumps from open-pit mines are numerous and continue to cause environmental problems. Because little reclamation occurred before about 1960 and mining started much earlier, abandoned mines are common in the United States. One surface mine in Wyoming, aban- doned more than 40 years ago, caused a disturbance so intense that vegetation has still not been reestablished on the waste dumps. Such barren, ruined landscapes empha- size the need for reclamation.

Strip Mining

Over half of the coal mining in the United States is done by strip mining, a surface mining process in which the overlying layer of soil and rock is stripped off to reach the coal (Figure 15.21). The practice of strip mining start- ed in the late 19th century and has steadily increased be- cause it tends to be cheaper and easier than underground mining. More than 40 billion metric tons of coal reserves are now accessible to surface mining techniques. In addi- tion, approximately 90 billion metric tons of coal within 50 m (165 ft) of the surface are potentially available for strip mining. More and larger strip mines will likely be developed as the demand for coal increases.

The impact of large strip mines varies from region to region, depending on topography, climate, and reclama- tion practices. One serious problem in the eastern United States that gets abundant rainfall is acid mine drainage—the drainage of acidic water from mine sites (see Chapter 19). Acid mine drainage occurs when surface water (H2O) in- filtrates the spoil banks (rock debris left after the coal is removed). The water reacts chemically with sulfide miner- als, such as pyrite (FeS2), a natural component of some sedimentary rocks containing coal, to produce sulfuric acid (H2SO4). The acid then pollutes streams and ground- water (Figure 15.22). Acid water also drains from under- ground mines and from roads cut in areas where coal and pyrite are abundant, but the problem of acid mine drain- age is magnified when large areas of disturbed material remain exposed to surface waters. Acid mine drainage from active mines can be minimized by channeling sur- face runoff or groundwater before it enters a mined area and diverting it around the potentially polluting materi- als. However, diversion is not feasible in heavily mined regions where spoil banks from unreclaimed mines may cover hundreds of square kilometers. In these areas, acid mine drainage will remain a long-term problem.

activities related to mining, such as exploration and road building. In some arid areas of the western and south- western United States, the land is so sensitive that tire tracks can remain for years. (Indeed, wagon tracks from the early days of the westward migration reportedly have survived in some locations.) To complicate matters, soils are often thin, water is scarce, and reclamation work is difficult.

Strip mining has the potential to pollute or damage water, land, and biological resources. However, good rec- lamation practices can minimize the damage. Reclama- tion practices required by law necessarily vary by site. For example, mining and reclamation of the Trapper Mine in Colorado (Figure 15.23) has been successful in part because there is sufficient precipitation (mostly snow) to reestablish vegetation without artificially applying water.

Large surface coal mining is almost always contro- versial. One of the most controversial has been the Black Mesa Mine in Arizona. The mine is in the Black Mesa area of the Hopi Reservation and was the only supplier of coal to the very large 1.5 MW Mohave Generating Station, a power plant at Laughlin, Nevada (144 km, or 90 mi, southeast of Las Vegas). The coal was delivered to the plant by a 440-km (275-mi) pipeline that transported slurry (crushed coal and water). The pipeline used over 1 billion gallons of water pumped from the ground per year—water that nourishes sacred springs and water for irrigation. Both the mine and the power plant suspended operation on December 31, 2005.

Mountaintop Removal

Coal mining in the Appalachian Mountains of West Virginia is a major component of the state’s economy. However, there is growing environmental concern about a strip-mining technique known as mountaintop re- moval (Figure 15.24). This technique is very effective in obtaining coal as it levels the tops of mountains. But as mountaintops are destroyed, valleys are filled with waste rock and other mine waste, and the flood hazard increas- es as toxic wastewater is stored behind coal-waste sludge dams. Several hundred mountains have been destroyed, and by 2103 over 3,840 km (2,400 mi) of stream chan- nels will likely have been damaged or destroyed.20

In October 2000, one of the worst environmen- tal disasters in the history of mining in the Appalachian Mountains occurred in southeastern Kentucky. About 1 million cu m (250 mil gal) of toxic, thick black coal sludge, produced when coal is processed, was released into the environment. Part of the bottom of the impoundment (reservoir) where the sludge was being stored collapsed, allowing the sludge to enter an abandoned mine beneath the impoundment. The abandoned mine had openings to the surface, and sludge emerging from the mine flowed across people’s yards and roads into a stream of the Big Sandy River drainage. About 100 km (65 mi) of stream was severely contaminated, killing several hundred thou- sand fish and other life in the stream.

Mountaintop removal also produces voluminous amounts of coal dust that settles on towns and fields, pol- luting the land and causing or exacerbating lung diseases, including asthma. Protests and complaints by communi- ties in the path of mining were formerly ignored but are now getting more attention from state mining boards. As people become better educated about mining laws, they are more effective in confronting mining companies to get them to reduce potentially adverse consequences of min- ing. However, much more needs to be done.

Those in favor of mountaintop mining emphasize its value to the local and regional economy. They further argue that only the mountaintops are removed, leaving most of the mountain, with only the small headwater streams filled with mining debris. They go on to say that the mining, following reclamation, produces flat land for a variety of uses, such as urban development, in a region where flat land is mostly on floodplains with fewer potential uses.

Since the adoption of the Surface Mining Control and Reclamation Act of 1977, the U.S. government has required that mined land be restored to support its pre- mining use. The regulations also prohibit mining on prime agricultural land and give farmers and ranchers the opportunity to restrict or prohibit mining on their land, even if they do not own the mineral rights. Reclamation includes disposing of wastes, contouring the land, and re- planting vegetation.

Reclamation is often difficult and unlikely to be com- pletely successful. In fact, some environmentalists argue that reclamation success stories are the exception and that strip mining should not be allowed in the semiarid south- western states because reclamation is uncertain in that fragile environment.

Underground Mining

Underground mining accounts for approximately 40% of the coal mined in the United States and poses special risks both for miners and for the environment. The dan- gers to miners have been well documented over the years in news stories, books, and films. Hazards include mine shaft collapses (cave-ins), explosions, fires, and respiratory illnesses, especially the well-known black lung disease, which is related to exposure to coal dust, which has killed or disabled many miners over the years.

Some of the environmental problems associated with underground mining include the following:

• Acid mine drainage and waste piles have polluted thousands of kilometers of streams (see Chapter 19).

• Land subsidence can occur over mines. Vertical subsid- ence occurs when the ground above a coal-mine tun- nel collapses, often leaving a crater-shaped pit at the surface. Coal-mining areas in Pennsylvania and West Virginia, for example, are well known for serious sub- sidence problems. In recent years, a parking lot and crane collapsed into a hole over a coal mine in Scran- ton, Pennsylvania; and damage from subsidence caused condemnation of many buildings in Fairmont, West Virginia.

• Coal fires in underground mines, either naturally caused or deliberately set, may belch smoke and hazardous fumes, causing people in the vicinity to suf- fer from a variety of respiratory diseases. For example, in Centralia, Pennsylvania, a trash fire set in 1961 lit nearby underground coal seams on fire. They are still burning today and have turned Centralia into a ghost town.

Transporting Coal

Transporting coal from mining areas to large population centers where energy is needed is a significant environ- mental issue. Although coal can be converted at the pro- duction site to electricity, synthetic oil, or synthetic gas, these alternatives have their own problems. Power plants for converting coal to electricity require water for cool- ing, and in semiarid coal regions of the western United States, there may not be sufficient water. Furthermore, transmitting electricity over long distances is inefficient and expensive. Converting coal to synthetic oil or gas also requires a huge amount of water, and the process is expensive.21,22

Freight trains and coal-slurry pipelines (designed to transport pulverized coal mixed with water) are options to transport the coal itself over long distances. Trains are typically used, and will continue to be used, because they provide relatively low-cost transportation compared with the cost of constructing pipelines. The economic advantages of slurry pipelines are tenuous, especially in the western United States where large volumes of water needed to transport the slurry are not easily available. In summary, the mining and use of about 900 million tons of coal per year in the United States is perhaps the biggest single source of pollution in the country today. Figure 15.25 summarizes some of the impacts discussed above. Promoting increased use of coal with- out providing much tighter environmental control of pollutants will continue to degrade our air, water, and land resources.23

The Future of Coal

The burning of coal produces about 40% of the electricity used in the United States today. This is down from 50% in recent years. More U.S. power plants are switching from coal to natural gas as the fuel of choice for economic and environmental reasons.

Coal, compared to natural gas, is much more pollut- ing. Emissions of nitrogen oxides are about five times as high, sulfur dioxide is 4,000 times as high, and particu- lates are 390 times as high for a unit energy output.

Legislation as part of the Clean Air Amendments of 1990 mandated that sulfur dioxide emissions from coal-burning power plants be eventually cut by 70– 90%, depending on the sulfur content of the coal, and that nitrogen oxide emissions be reduced by about 2 million metric tons per year. As a result of this legisla- tion, utility companies that burn coal are struggling with various new technologies designed to reduce emissions of sulfur dioxide and nitrogen oxides from burning coal. Options being used or developed include the following:22,24

• Chemical and/or physical cleaning of coal prior to combustion.

• Producing new boiler designs that permit a lower tem- perature of combustion, reducing emissions of nitro- gen oxides.

• Injecting material rich in calcium carbonate (such as pulverized limestone or lime) into the gases produced by the burning of coal. This practice, known as scrub- bing, removes sulfur dioxides. In the scrubber—a large, expensive component of a power plant—the

carbonate reacts with sulfur dioxide, producing hy- drated calcium sulfite as sludge. The sludge has to be collected and disposed of, which is a major problem.

• Converting coal at power plants into a gas (syngas, a methane-like gas) before burning. This technology is being tested and may become commercial by 2013 at the Polk Power Station in Florida. The syngas, though cleaner burning than coal, is still more polluting than natural gas.

• Converting coal to oil: We have known how to make oil (gasoline) from coal for decades. Until now, it has been thought to be too expensive. South Africa is performing this conversion now, producing over 150,000 barrels of oil per day from coal, and in 2009 China finished construction of a conversion plant in Mongolia. In the United States, we could produce 2.5 million barrels per day, which would require about 500 million tons of coal per year by 2020. There are envi- ronmental consequences, however, as superheating coal to produce oil generates a lot of carbon dioxide (CO2), the major greenhouse gas.

• Educating consumers about energy conservation and efficiency to reduce the demand for energy and, thus, the amount of coal burned and emissions released.

• Developing zero-emission coal-burning electric pow- er plants. Emissions of particulates, mercury, sulfur dioxides, and other pollutants would be eliminated by physical and chemical processes. Carbon diox- ide would be eliminated by injecting it deep into the earth or using a chemical process to sequester it (tie it up) with calcium or magnesium as a solid. The concept of zero emission is in the experimental stages of development.

Coal mining and burning coal will continue to have significant environmental impacts for several reasons:

• More and more land will be stripmined and will therefore require careful and expensive restoration.

• Unlike oil and gas, burning coal produces large amounts of air pollutants. It also creates ash, which can be as much as 20% of the coal burned; boiler slag, a rock-like cinder produced in the furnace; and calcium sulfite sludge, formed when removing sul- fur through scrubbing. Coal-burning power plants in the United States today produce about 90 million tons of these materials per year. Calcium sulfite from scrubbing can be used to make wallboard (by con- verting calcium sulfite to calcium sulfate, which is

gypsum) and other products. Gypsum is being pro- duced for wallboard in this way in Japan and Ger- many, but the United States can make wallboard less expensively from abundant natural gypsum deposits. Another waste product, boiler slag, can be used for fill along railroad tracks and at construction projects. Nevertheless, about 75% of the combustion products of burning coal in the United States today end up in waste piles or landfills.

• Handling large quantities of coal through all stages (mining, processing, shipping, combustion, and fi- nal disposal of ash) has adverse environmental effects. These include aesthetic degradation, noise, dust, and— most significant from a health standpoint—release of toxic or otherwise harmful trace elements into the wa- ter, soil, and air. For example, in late December 2008, the retaining structure of an ash pond at the Kingston Fossil Plant in Tennessee failed, releasing a flood of ash and water that destroyed several homes, ruptured a gas line, and polluted a river.25

All of these negative effects notwithstanding, it seems unlikely that the United States will abandon coal in the near future because we have so much of it and have spent so much time and money developing coal resources. Re- gardless, it remains a fact that coal is the most polluting of all the fossil fuels.

Allowance Trading

An approach to managing U.S. coal resources and reducing pollution is allowance trading, through which the Environmental Protection Agency grants utility companies tradable allowances for polluting: One al- lowance is good for one ton of sulfur dioxide emissions per year. In theory, some companies wouldn’t need all their allowances because they use low-sulfur coal or new equipment and methods that have reduced their emissions. Their extra allowances could then be traded and sold by brokers to utility companies that are un- able to stay within their allocated emission levels. The idea is to encourage competition in the utility industry and reduce overall pollution through economic market forces.24

Some environmentalists do not accept the concept of allowance trading. They argue that although buying and selling may be profitable to both parties in the transac- tion, it is less acceptable from an environmental view- point. They believe that companies should not be able to buy their way out of taking responsibility for pollution problems.

SUMMARY

• Fossil fuels are forms of stored solar energy. Most of these fuels are created from the incomplete biological decompo- sition of dead and buried organic material that is convert- ed by complex chemical reactions in the geologic cycle.

• Because fossil fuels are nonrenewable, we will eventually have to develop other sources to meet our energy demands. We must decide when the transition to alternative fuels will occur and what the impacts of the transition will be.

• Environmental impacts related to oil and natural gas include those associated with exploration and develop- ment (damage to fragile ecosystems, water pollution, air pollution, and waste disposal); those associated with refining and processing (pollution of soil, water, and air); and those associated with burning oil and gas for energy to power automobiles, produce electricity, run industrial machinery, heat homes, and so on (air pollution).

• Today, the United States is undergoing a fossil fuel revo- lution as abundant new supplies of conventional and continuous oil and gas are being developed. The revolu- tion will have profound economic and environmental consequences.

• Coal remains an important resource for producing elec- tric power, but the new abundance of cleaner burning natural gas is likely to surpass coal as the fuel of choice in the coming decades.

• Coal is an energy source that is particularly damaging to the environment. The environmental impacts of min- ing, processing, transporting, and using coal are many. Mining coal can cause fires, subsidence, acid mine drainage, and difficulties related to land reclamation. Burning coal can release air pollutants, including sulfur dioxide and carbon dioxide, and it produces a large vol- ume of combustion products and by-products, such as ash, slag, and calcium sulfite (from scrubbing).

• It has been argued that we cannot achieve sustainable development and maintenance of a quality environ- ment for future generations if we continue to increase our use of fossil fuels. Achieving sustainability will require wider use of a variety of alternative renewable energy sources and less dependence on fossil fuels.

Botkin, Daniel B. Environmental Science: Earth as a Living Planet, 9th Edition. Wiley, 2013-12-23. VitalBook file.

Multimedia

1. Bryce, R. (2011, November 30). What’s a watt? [Video clip]. Retrieved from http://www.youtube.com/watch?v=1__KjuGNzxc

· Transcript

2. energynownews. (2011, July 14). What you don’t know about gas prices [Video clip]. Retrieved from http://www.youtube.com/watch?v=yQaRaCtCuzE

· Transcript

3. energynownews. (2011, October 3). Energy 101: Electricity generation [Video clip]. Retrieved from http://www.youtube.com/watch?v=20Vb6hlLQSg

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4. Hickey, K. (2010, July 1). Life cycle assessment – It’s the only way to drive! [Video clip]. Retrieved from http://www.youtube.com/watch?v=ZlJ3HKXSdhc

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Recommended Resources Websites

1. Department of Energy. (n.d.). Energy sources. Retrieved from http://energy.gov/science-innovation/energy-sources

2. Department of Energy. (n.d.). Fossil. Retrieved from http://energy.gov/science-innovation/energy-sources/fossil