LESSON

2

Fossil Fuels Guiding Question: How did fossil fuels form, and how are they obtained and used?

• Explain how fossil fuels formed. • Describe the uses of coal and how it is removed from the ground. • Describe the uses of oil and how it is extracted. • Explain the characteristics and uses of natural gas. • Predict the future of fossil fuels.

Reading Strategy Before you read, preview Figure 6, which shows how coal formed. Write any questions you have about the illustration. Answer these questions when you read the lesson. Vocabulary strip mining, subsurface mining, petroleum, petrochemical, oil sands, oil shale, methane hydrate

“DOWN BY THE STATION, early in the morning, see the little

pufferbellies all in a row.” When you hear that old children’s song, do you ever wonder what a pufferbelly is? Pufferbelly is a slang term for a steam locomotive. Many years ago, railroad trains were powered by steam, and that steam usually came from water heated by burning coal. Today most trains run on diesel fuel or electricity, not steam produced by coal fires. Both diesel fuel and the coal that powered the old steam locomotives are fossil fuels. All fossil fuels are nonrenewable energy resources. These nonrenewable fuels were produced by processes that are still happening today. However, these processes do not create fossil fuels nearly fast enough to replace the ones we are using up. To replenish all the fossil fuels we have used so far would take many millions of years.

How Fossil Fuels Form Fossil fuels form from the remains of organisms that lived millions of years ago.

17.2 Lesson Plan Preview

Inquiry  Students investigate how people have historically used coal.
 Real World  Students make lists of products they use everyday that contain petroleum.
 Differentiated Instruction  English language learners learn different uses of the word gas.

17.2 Resources Paper and Pencil Activity, Fossil Fuel Use • Bellringer Video, Coal Mines—Integral to the Economy • Graph It, Global Oil Production and the Hubbert Curve • Chapter 17 Overview Presentation

522  Lesson 2

Fossil fuels, including coal, oil, and natural gas, are formed from the remains of once-living organisms. The energy in these fuels comes originally from the sun. During photosynthesis, electromagnetic energy from the sun is converted to chemical energy stored in complex molecules. Over millions of years, some of these molecules undergo a series of changes that eventually result in fossil fuels. Fossil fuels are composed mostly of hydrocarbons. Hydrocarbons are chemical compounds made mainly of hydrogen and carbon atoms.

Breakdown Without Oxygen  After they die, most organisms do

not end up as part of a coal, gas, or oil deposit. Fossil fuels are produced only when the remains of living things are broken down in an environment that has little or no oxygen, such as the bottoms of deep lakes, swamps, and shallow seas. As dead organisms gradually accumulate at the bottoms of these bodies of water, sediments may accumulate on top of the the remains and exert pressure on them.

Different Conditions, Different Fuels  The remains of organisms may be converted into crude oil, natural gas, or coal. Various factors, such as temperature, amount of pressure, and the chemical composition of the starting material, determine which fossil fuels are produced. Oil, for example, comes from the remains of organisms such as microscopic animals and algae. These organisms live in oceans and inland seas. Coal forms from plant remains that are compressed under very high pressure. Figure 6 shows how coal forms. First, peat forms as plants die and fall into a lake, bog, or swamp. Then, coal forms over millions of years, under increasing heat and pressure. Notice that there are different types of coal. Lignite has the lowest energy value, and anthracite typically has the highest.

Coal Coal, which is used mainly to generate electricity, is obtained by mining. Coal is the world’s most abundant fossil fuel, and its use goes back to ancient times. People in parts of China have heated with coal for at least 2000 years. In Britain, during the second and third centuries of the modern era, the ancient Roman invading armies used coal for heating. Beginning in the 1300s, in what is now the southwestern part of the United States, Native Americans of the Hopi Nation used coal to heat their homes, cook food, and fire pottery. North America has abundant coal reserves. One quarter of the world’s coal is located in the United States. Asia, too, is rich in coal. Today, China and the United States are the main producers and users of coal. Reading Checkpoint

What nations are the main producers of coal today?

FOCUS  Watch the ABC News video Coal Mines—Integral to the Economy. Use the information in the video to launch a discussion of the importance of coal as an energy source in the United States. BIG QUESTION Can we depend on nonrenewable energy resources for our energy needs? Explanation  After students have read about coal formation, help them use what they have learned to expand their understanding of the Big Question. First, have students write a sentence that relates the length of time required for coal to form to coal’s classification as a nonrenewable energy resource. Then, have students apply their knowledge of coal formation to develop and support an opinion about whether people can use nonrenewable energy resources for all of their energy needs. ANSWERS

Reading Checkpoint  China and the United States

Ancient forest Increasing heat and pressure

Peat

Lignite

SubBituminous bituminous Time

Anthracite

FIGURE 6  How Coal Forms Coal forms as ancient plant matter is compacted underground. Notice that peat forms before coal, and that there are four types of coal. The type of coal that forms depends on conditions such as heat and pressure. Nonrenewable Energy  523

Surface

Ventilation Main Shaft Surface

Coal deposits

(a) Strip mining

(b) Subsurface mining

FIGURE 7  Mining for Coal  Coal is mined in two ways. (a) Strip mining is used when the coal is near the surface of the ground. (b) If the coal is deep underground, it is removed by subsurface mining.

Find Out More

Coal deposits

How Coal Is Used  Coal provides one fourth of the world’s energy.

Coal-fired steam engines helped drive the Industrial Revolution, powering factories, trains, and ships. In the 1880s, people began to use coal to generate electricity. Today, coal generates about half the electricity used by Americans. In addition, coal powers many industries. Some of these industries are chemical manufacturing, iron and steel manufacturing, and paper mills.

Mining for Coal  We use two major methods to remove coal from the

ground. Look at Figure 7 as you read about these methods. ANSWERS

Find Out More  Answers will vary, but should indicate that students have used reliable resources to learn more about heating methods used in their houses or apartments.

Find Out More How is your apartment or house heated? Does this method depend on fossil fuels? Ask your parents or the building superintendent for this information. Use a library or Internet resources to find out the advantages and disadvantages of this type of heating. 524  Lesson 2

When coal deposits are at or near the surface, strip mining is used. Strip mining is the extraction of a mineral by removing a strip of the layers of soil and rock on top of the mineral deposit. Strip mining may remove huge amounts of soil and rock. Once the coal is exposed, it can be extracted. After the coal has been removed, the soil may be put back to fill the holes. Strip mining operations can extend over a large area. In some cases, entire mountaintops are blasted away.

▶ Strip Mining 

We reach underground deposits with subsurface mining. Subsurface mining is typically the practice of digging shafts deep into the ground to find and remove a mineral. Networks of tunnels are usually blasted with explosives and then dug out so that miners can reach the coal. After miners dig the coal out, it is brought to the surface.

▶ Subsurface Mining 

Advantages of Coal  There are several reasons why coal is used commonly as an energy source. Compared to other fossil fuels, coal is more abundant and less expensive. It does not need much processing after it has been removed from the ground. Coal can be transported relatively easily in trucks and trains. Unlike the oil taken from Prudhoe Bay in Alaska, coal does not require a pipeline.

Oil Petroleum, which is obtained by drilling, is a major source of energy and is used to make a variety of products. Oil, or petroleum, is a dark, liquid fossil fuel made up mostly of hydrocarbons. Petroleum is found in underground deposits. The Middle East is especially rich in these deposits. Petroleum is also found in other parts of the world, such as Russia, and North and South America.

How Petroleum Is Used  Petroleum is the source of the fuels used for most forms of transportation, such as cars, trucks, airplanes, and ships. Many people heat their homes with fuel oil. Because oil is a complex mix of hydrocarbons, it can be used to make many types of products. Petrochemicals are chemical compounds that are derived from oil and used to make products. Figure 8 shows some petroleum products that are used in and around a home. Finding Petroleum Deposits  Most oil deposits are deep under-

ground. There, the oil is usually found within tiny pores, or holes, in rocks such as sandstone and limestone. Rocks containing oil are a little bit like a sponge that has soaked up water. Scientists look for oil by performing various tests. For example, they send sound waves deep underground and determine how long it takes the waves to be reflected and to reach different surface locations. The length of time can indicate the characteristics of the rocks the waves pass through. Once scientists find a likely location, oil companies drill deep holes and remove rock cores to see whether the rocks contain oil. Reading Checkpoint

What is petroleum composed of?

ANSWERS

Reading Checkpoint  Petroleum is composed mostly of hydrocarbons. FIGURE 8  Petroleum Products  Many products, such as those shown here, are derived from petroleum.

Nonrenewable Energy  525

Oil rig Oil well

Ocean floor

Oil in pores of rocks (a) Primary extraction of oil

Drilling for Oil  You squeeze a sponge to remove the water. Similarly, pressure is needed to get oil from porous rock. Usually, oil trapped in rocks is already under pressure. So at first, oil will rise in the well, often all the way to the surface, without needing to be pumped out. During that period, a process called primary extraction can be used to remove the oil, as shown in Figure 9. Later, once the pressure decreases, oil companies use a process called secondary extraction to get the oil to the surface. In secondary extraction, chemicals may be used to dissolve oil. Secondary extraction may also involve pumping water, steam, or gases such as carbon dioxide beneath oil deposits to force the oil to the surface. At Prudhoe Bay in Alaska, seawater is piped into wells to flush out oil. Oil drilling takes place not just on land but on the seafloor in relatively shallow water. Refining Oil  Oil taken out of the ground is called crude

oil. Crude oil cannot be used the way it is. It must be refined in order to be usable. Refining involves separating crude oil into different fuels and other substances. This process takes place in a refinery. Reading Checkpoint

Oil rig

Oil well Seawater injection

Gas injection Ocean floor

Pressure

Oil in pores of rocks

(b) Secondary extraction of oil

FIGURE 9  Extracting Oil  (a) Primary extraction is used when the oil deposit is already under pressure. (b) Once the pressure decreases, secondary extraction is used, which involves injecting water or gas to force the oil upward.  Apply Concepts  Which technique is now used for removing oil from the Prudhoe Bay area? 526  Lesson 2

Describe primary extraction.

Natural Gas Natural gas yields a large amount of energy and is less polluting than other fossil fuels. Natural gas consists of the gas methane mixed in with small amounts of other gases. Its use is growing faster than that of most other fossil fuels today. Natural gas is colorless and odorless. It is much less polluting than coal or oil, and it emits less carbon dioxide per unit of energy produced than either coal or oil. Natural gas produces a large amount of energy. Pockets of natural gas are often located above oil deposits, both on land and offshore. Coal deposits, too, may have natural gas above them. Within the United States, pipelines carry natural gas from its source to where it is used. If laid end to end, our network of natural gas pipelines would go to the moon and back twice. About half the homes in the United States are heated by natural gas, as are many businesses. Appliances such as water heaters, stoves, and clothes dryers may use natural gas to produce heat. Increasingly, natural gas is used to generate electricity, because it does not pollute the atmosphere to the extent that coal does. Natural gas goes into products such as paints, plastics, dyes, and fertilizers.

The Supply of Fossil Fuels

World Consumption of Fossil Fuels 1980–2006

The supply of fossil fuels is limited. Global consumption of coal, oil, and natural gas has risen steadily for years, and it continues to rise. Figure 10 shows this trend. Right now, all the coal, oil, and natural gas that will be available to human society have already formed. What will happen when easily obtainable supplies of fossil fuels begin to run out?

Dwindling Deposits  No one knows the exact amount of fossil

fuels that are left or how long they will last. The most accessible reserves of natural gas, oil, and coal have already been used up. Remaining deposits of fossil fuels are often difficult and expensive to extract. The technology for extracting and producing fossil fuels will probably continue to improve. However, as people continue to remove fossil fuels, it is becoming harder and harder to find new sources. Some scientists and oil-industry experts calculate that we have already extracted nearly half of the world’s oil reserves. Many scientists predict that the worldwide production of oil will decrease over the next few decades. Figure 11 shows a graph of one prediction for what will happen to oil production. And many scientists and experts think that we will face a crisis long before the last drop of oil is pumped from a well. If the demand for oil continues to increase, there will be a shortage when the rate of oil production first starts going down. Reserves of coal are expected to last significantly longer than oil. In fact, one projection indicates that coal supplies will last 130 years in the United States. But even supplies of coal, the most abundant fossil fuel, will not last forever.

Wolrd Consumption (quadrillion Btu)

200 150 Petroleum 100

Coal Natural gas

50 0 1980

1990 Year

2000 2006

Source: Data from U.S. Energy Information Administration, International Energy Annual 2006.

FIGURE 10  Consumption of Fossil Fuels  The graph shows how the use of petroleum, coal, and natural gas increased between 1980 and 2006. ANSWERS

Reading Checkpoint  Primary extraction is a method of removing oil from rocks using the pressure that already exists. Figure 9  Secondary extraction Figure 11  Opinions will vary. Some students may think that diminishing oil supplies justify drilling for oil in the Arctic Refuge. Others may argue that the Alaskan environment needs to be preserved.

Modern Prediction of Peak in Global Oil Production 30

Billion barrels per year

25

Middle East Russia

Europe Lower 48 U.S. states

Other

20 FIGURE 11  Oil Production  The graph shows how much oil has been produced worldwide since 1930 and one prediction for the amount of oil to be produced in the future. Interpret Graphs Does this graph affect your opinion about drilling in the Arctic Refuge? Explain your answer.

15 10 5 0 1930

1950

1970

1990 Year

Data from Campbell, C.J., and Association for the Study of Peak Oil. 2007.

2010

2030

2050 Global Oil Production and the Hubbert Curve

Nonrenewable Energy  527

New Sources of Fossil Fuels  Are there other fossil fuels that

can replace or supplement oil, natural gas, and coal? Oil sands, oil shale, and methane hydrate may be alternative sources of fossil fuels. Oil sands are deposits of moist sand and clay containing bitumen. Bitumen is a thick, heavy form of petroleum that is rich in carbon. Oil sands are generally removed by strip mining. After extraction, bitumen is refined into a more valuable synthetic crude oil. Petroleum prices are rising, and this fact makes oil sands more profitable than they once were.

▶ Oil Sands 

FIGURE 12  Oil Shale  If it is lighted, oil

shale will continue to burn on its own. Oil shale may be a future source of oil.

Oil shale is rock filled with a mixture of hydrocarbons. Once mined, oil shale can be burned directly, like coal. Alternatively, it can be processed to extract liquid petroleum. The world’s known deposits of oil shale may be able to produce a large amount of oil. As crude oil prices rise, oil shale is attracting a large amount of attention.

▶ Oil Shale 

The deep ocean floor contains a possible source of energy, methane hydrate. Methane hydrate is an icelike solid that consists of molecules of methane within a crystal network of water molecules. Methane hydrate can be burned to release energy. Scientists think there is a huge amount of methane hydrate on Earth. However, they still need to find a way to extract methane hydrate safely, without causing underwater landslides.

▶ Methane Hydrate 

Alternative fossil fuels are abundant, but they will not solve our energy challenges. They are expensive to extract and process. Because it takes a lot of energy to extract alternative fossil fuels, they provide much less net energy than conventional fossil fuels do. (Net energy is the energy provided by a source after the energy used to obtain the source has been subtracted.) In addition, the extraction of alternative fossil fuels can cause environmental damage. For example, strip mining is used to extract oil sands and oil shale, and strip mining removes topsoil and vegetation. The most serious environmental effect of these fuels is that their combustion releases greenhouse gases. Therefore, the use of these fuels would speed up climate change.

▶ Drawbacks 

ANSWERS

Lesson 2 Assessment  For answers to the Lesson 2 Assessment, see page A–27 at the back of the book.

2 1. Review  Where did the energy in fossil fuels originally come from? What type of energy is stored in fossil fuels? 2. Compare and Contrast  What are two major methods of obtaining coal from the ground? Compare these two methods. 3. Use Analogies  How are rocks that contain oil similar to a sponge?

528  Lesson 2

4. Apply Concepts  What is one advantage that natural gas has over coal and oil? 5. Relate Cause and Effect  Why is the supply of fossil fuels dwindling? 6. Explore the BIGQUESTION   The cost of researching technology to extract alternative fossil fuels, such as oil sands and oil shale, is high. Do you think this is a wise investment? Explain your answer.