Environmental science

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

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The Deepwater Horizon drilling rig on fire, April 2010

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Essential Environment: The Science Behind the Stories, Fourth Edition, by Jay Withgott and Matthew Laposata. Published by Benjamin Cummings. Copyright © 2012 by Pearson Education, Inc.

G A R R E T T , M E G A N 1 3 2 4 T S

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

CENTRAL CASE STUDY

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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Essential Environment: The Science Behind the Stories, Fourth Edition, by Jay Withgott and Matthew Laposata. Published by Benjamin Cummings. Copyright © 2012 by Pearson Education, Inc.

G A R R E T T , M E G A N 1 3 2 4 T S

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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Essential Environment: The Science Behind the Stories, Fourth Edition, by Jay Withgott and Matthew Laposata. Published by Benjamin Cummings. Copyright © 2012 by Pearson Education, Inc.

G A R R E T T , M E G A N 1 3 2 4 T S

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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Essential Environment: The Science Behind the Stories, Fourth Edition, by Jay Withgott and Matthew Laposata. Published by Benjamin Cummings. Copyright © 2012 by Pearson Education, Inc.

G A R R E T T , M E G A N 1 3 2 4 T S

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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Essential Environment: The Science Behind the Stories, Fourth Edition, by Jay Withgott and Matthew Laposata. Published by Benjamin Cummings. Copyright © 2012 by Pearson Education, Inc.

G A R R E T T , M E G A N 1 3 2 4 T S

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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Essential Environment: The Science Behind the Stories, Fourth Edition, by Jay Withgott and Matthew Laposata. Published by Benjamin Cummings. Copyright © 2012 by Pearson Education, Inc.

G A R R E T T , M E G A N 1 3 2 4 T S

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 seafloor 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 floating 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

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