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Chapter11.pdf

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Environment Tenth Edition

Raven

Chapter 11

Fossil Fuels

Fossil Fuels (1 of 2)

Overview of Chapter 11

• Fossil Fuels

• Coal

• Oil and Natural Gas Extraction and Consumption

• Environmental Impacts of Oil and Natural Gas

• Synfuels and other Potential Fossil Fuel Resources

Deep Water Horizon Oil Spill

• April 2010 explosion, British Petroleum platform

• 4 million barrels of crude oil spill into Gulf of Mexico

• Killed 11 oil rig workers

• Costs and benefits of using fossil fuels as energy source

• Long-term impacts will be huge, difficult to assess

Fossil Fuels (2 of 2)

• Fossil Fuels- Combustible deposits in the Earth’s crust o Composed of the remnants (fossils) of prehistoric organisms

that existed millions of years ago

o Includes coal, oil (petroleum) and natural gas

• Supply over 80% of energy used in North America

• Non-renewable resource o Fossil fuels are created too slowly to replace the reserves we

use

How Are Fossil Fuels Formed?

• ~ 300 million years ago o Climate was mild

o Vast swamps covered much of the land

o Dead plant material decayed slowly in swamp environment

Formation of Each Fossil Fuel

• Coal o Heat, pressure, and time turned the nondecomposed plant

material into carbon-rich rock (coal)

• Oil o Microscopic plants buried under sediment

o Heat, pressure, and time turned them into hydrocarbons (oil)

• Natural Gas o Formed the same way as oil, but at temperatures higher than

100 degree Celsius

Fossil Fuels, Carbon Cycle, Climate

• Burning releases C as CO2 o C from plants that fixed the CO2 (via photosynthesis) existed

over 300 mya

• Increasing the export of CO2 to atmosphere, but not increasing fixation

• Natural cycles change slowly

• Burning is quick change – out of balance

Coal (1 of 2)

• A black, combustible solid composed mainly of carbon, water, and trace elements found in Earth’s crust

• Most, if not all, coal deposits have been identified

• Occurs in different grades- based on variations in heat and pressure during burial o Energy density – energy per volume

Coal (2 of 2)

Table 11.1 A Comparison of Different Kinds of Coal

Type of Coal Color

Water Content (%)

Relative Sulfur Content

Carbon Content (%)

Average Heat Value (BTU/pound)

2015 Cost at Mine for 2000 lb of Coal ($)

Lignite Dark brown

45 Medium 30 6000 22.36

Subbituminous coal

Dull black

20–30 Low 40 9000 14.63

Bituminous coal

Black 5–15 High 50–70 13,000 51.57

Anthracite Black 4 Low 90 14,000 97.91

Sources: EIA, U.S. Department of Energy, and USGS.

Facts on Coal

• Coal is highly flammable

• Dangerous to mine

• Burning and mining releases pollutants

• 90,000 miner deaths during 20th century o Increased risk of lung

disease and cancer

o 2,000 die each year from diseases

Coal Supplies and Consumption

• U.S. has 20% of world’s coal supplies

• Known coal deposits could last 200 years o At present rate of consumption

Surface Mining of Coal

• Coal usually found in seams that vary from 1in to 100ft in thickness

• Surface mining (below) o Chosen if coal is within 100ft

of surface

o Ex: Strip mining

o Defined: extraction of resources near surface by removing the soil, subsoil, and overlying rock strata (i.e., the overburden)

Subsurface Mining of Coal

• Extraction of mineral and energy resources from deep underground deposits

• ~40% of current mining is subsurface

• More expensive and less safe than surface mining o More difficult to fully remove coal with subsurface mining

• However, less destructive to landscapes than surface mining

Environmental Impacts of Mining Coal

• Surface Mining Control and Reclamation Act (1977) o Requires filling (reclaiming) of surface mines after mining

o Reduces Acid Mine Drainage

o Requires permits and inspections of active coal mining sights

o Prohibits coal mining in sensitive areas

• Land with mines abandoned prior to 1977 are slowly being restored

Acid Mine Drainage

• Pollution caused when sulfuric acid and dissolved materials, such as lead, arsenic, and cadmium, wash from coal and metal mines into nearby lakes and streams

• Rainwater seeps inside exposed mine wastes

• Contaminates soils

Mountain Top Removal - Before

• Topography before mining

Mountain Top Removal - After

• Topography after mining

Environmental Impacts of Burning Coal

• Releases large quantities of CO2 into atmosphere o Greenhouse gas

• Releases other pollutants into atmosphere o Mercury

o Sulfur oxides

o Nitrogen oxides

• Can cause acid deposition o Rainwater ~5.6 pH, acid rain ~2.1 (lemon juice)

Making Coal Cleaner

• Scrubbers - desulfurization systems o Remove 98–99% of sulfur from power plant’s exhaust

o Expensive

o Sludge byproduct must be disposed of

• Sludge and fly ash are part of resource recovery o Marketable product from wastes

• Nationwide cap of SO2 and nitrogen oxide emissions

Cleaner Method - Fluidized Bed Combustion

• Crushed coal mixed with limestone to neutralize acidic sulfur compounds produced during combustion process

Regulation of CO2 emissions

• EPA can regulate CO2 emissions o 2014 U.S. Supreme Court decision

o Controversy because CO2 is a natural product of respiration and organisms

• Push for carbon capture and storage (CCS) o Removal of carbon from fossil-fuel combustion and storage of

the carbon, usually underground

o New power plants store CO2 when released

o Initially expensive to install technology

o Worry about where and how to ‘store’ the captured CO2

Oil and Natural Gas Extraction and Consumption

• Oil and natural gas important after 1930s o More versatile, easier to

transport, cleaner to burn

• Oil provides ~36.9% and natural gas ~29.3% of U.S. energy (2016)

• They provide

of world’s energy combined ~ 55%

Petroleum Refining

• Refining separates numerous hydrocarbons present in crude oil (petroleum) o Based on boiling point

• Natural gas contains far fewer hydrocarbons than crude oil o Methane, ethane, propane, and

butane

Natural Gas

• Contains only methane, ethane, propane, and butane o Propane and butane are used for cooking and heating in

rural areas

o Methane used for heat and to generate electricity in power plants

• Natural gas increasingly used for electricity, transportation, and commercial cooling o In vehicles, emits 93% fewer hydrocarbons, 90% less carbon

monoxide and 90% fewer toxic emissions than gasoline

Storing Liquefied Natural Gas

• Gas first compressed into liquefied natural gas (LNG)

Oil and Natural Gas Exploration

• Oil and natural gas migrate upwards until they hit impermeable rock

• Usually located in structural traps o Underground geologic structures that tend to trap any oil or

natural gas, if present

Oil Reserves

• Globally present, but unevenly distributed

• More than half is located in the Persian Gulf

Natural Gas Reserves

• Uneven distribution globally

• 42% located in two countries: Russia and Iran

How Long Will Supplies Last?

• May have already reached peak oil

• Depends on: o Locating more deposits

o Future extraction technologies

o Changes in global consumption rates

Marcellus Shale

• Huge store of natural gas in U.S.

• Major deposits beneath sections of 6 states o Major shale deposits found

under 24 states

• Shale gas more difficult to extract than in sandstone o Requires fracturing of rock

via hydraulic fracturing

Hydraulic Fracturing

• Extraction of natural gas that is tightly bound in shale deposits by applying chemicals and water under high pressure

• Produces large amounts of contaminated wastewater o Push to recycle water

o Wastewater generally stored deep underground

Very controversial o Regulations slow

o Pennsylvania – many wells, N.Y - few

Extraction with Hydraulic Fracturing

Environmental Impacts of Oil and Natural Gas • Combustion

o Increases CO2 and pollutant emissions

o Natural gas is far cleaner burning than oil

• Production o Disturbance to land and habitat

• Transport o Spills- especially in aquatic systems

o Ex: Coast of Spain Oil Spill (2002) – halted fishing industry

Deepwater Horizon Oil Spill (2010)

• April 22, 2010 - Deepwater Horizon, a drilling platform in the Gulf of Mexico, exploded o Flow of oil from the oil well

was finally stopped in mid-July 2010

o 5 million barrels of oil flowed into ocean

o Most rose to surface where it spread

• 2Nearly 29,000 mi of ocean were covered

Extent of Deepwater Horizon Spill

Exxon Valdez Oil Spill (1989)

• Exxon Valdez hit a reef and spilled 260,000 barrels of crude oil into sound

• Largest oil spill in U.S. history

• Led to Oil Pollution Act of 1990

• Huge decline in seal and killer whale populations

Extent of Exxon Valdez Oil Spill

Arctic National Wildlife Refuge (ANWR)

• Controversy to open ANWR more

• Many stakeholders o Alaskan natives

o Energy corporations

o Politicians

o Citizens – gas prices

o Domestic energy reliance

Synthetic Fuels (Synfuels)

• A liquid or gaseous fuel that is synthesized from coal and other naturally occurring sources o A substitute for oil or natural gas

• Tar sands (bitumen)

o Bitumen difficult to remove- must heat it underground with steam to make it flow

o Refined like crude oil, uses more energy

• Oil shales (kerogen) o Crushed and heated to yield oil

Synfuels

• Gas hydrates (methane hydrates) o Ice encrusted natural gas deep under

permafrost in arctic

• Liquefied coal o Liquid produced from coal

o Expensive to produce but cost decreasing

• Coal gas (right) o Burns as cleanly as natural gas

Environmental Impact of Synfuels

• Many of same undesirable effects as fossil fuels o Contributes to global warming, air pollution

• Coal gas requires large amount of water to extract o Mostly located in areas very short on water

• Recovering fuels in tar sands and oil shales would require extensive surface mining o Very environmentally dirty and more CO2 during production

than other fuels

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