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7 Sustaining Our Energy Resources

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Learning Outcomes

After reading this chapter, you should be able to

• Define basic energy concepts. • Describe current energy sources and uses and how that might change in the future. • Explain how fossil fuels are formed. • Analyze the impact and future of coal. • Analyze the impact and future of oil. • Analyze the impact and future of natural gas. • Analyze the impact and future of nuclear energy. • Describe the opportunities and challenges of the energy transition. • Identify examples of energy efficiency and conservation. • Analyze the impact and future of solar energy. • Analyze the impact and future of wind energy. • Analyze the impact and future of bioenergy. • Analyze the impact and future of hydroelectric energy, geothermal energy, and ocean energy. • Describe what goes into the true cost of energy and what policies might be enacted to

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Section 7.1 Our Current Energy System

Much like water, energy is a resource we use every day without ever really giving much thought to where it comes from or what the consequences of its use are for the planet. Take a casual inventory of your home or apartment and consider all the devices and consumer products that are currently plugged into a wall outlet. Televisions, computers, refrigerators, microwave ovens, toasters, cell phone chargers, and other consumer products are constant users of energy, day in and day out.

Now consider that your household is only 1 of about 130 million households in the United States, and only 1 of about 1.6 billion households worldwide. Now add to this all the energy that you and others use outside of your home—for transportation, while at work, and in other settings like schools and hospitals. Finally, add to that all the energy used worldwide by com- mercial businesses and industries to produce, package, transport, and deliver all the items you consume every day—your food, water, clothing, and other consumer products.

The sheer scale of global energy use would seem to make its measurement almost impossible, and yet every year experts at the U.S. Energy Information Administration (EIA) do just that. The EIA estimates that global energy consumption in 2018 was almost 600 quadrillion Brit- ish thermal units (Btu). This compares with global energy use of about 360 quadrillion Btu (quads) in 1990, 400 quads in 2000, and 500 quads in 2010. Furthermore, the EIA (2018) projects global energy use to increase to 739 quads by 2040.

It’s difficult to attach a human scale to these numbers. What is a Btu, and what does it mean to use 600 quadrillion (600 with 15 zeros added) of them? Technically, a Btu is the amount of heat energy required to raise the temperature of 1 pound of water by 1 degree Fahrenheit. Six hundred quadrillion Btu is roughly equivalent to the amount of energy in 27 billion metric tons of coal or 102 billion barrels of oil. In reality, even these measures are difficult to com- prehend in the abstract. What we can say, however, is that global energy use is massive and growing.

Our global energy use is also highly destructive to the environment. We currently depend to a great extent on coal, oil, and natural gas to meet our energy needs. These resources are finite, and the extraction and use of these fuels contributes to water pollution, air pollution, ecosystem destruction, and global climate change, among other environmental impacts. Envi- ronmental scientists are more convinced than ever that we need to move away from what are known as nonrenewable sources of energy to renewable sources, including solar and wind. Such an energy transition is already under way. The question is whether it can happen fast enough to avoid the worst of the environmental impacts described.

7.1 Our Current Energy System

While we may hear the term energy used frequently in the news, in political debates, and in discussions of environmental issues, we seldom take the time to ask what that term means. Recall from Chapter 2 that energy is the capacity to do work. Sunlight (solar energy) enables plants to photosynthesize and grow. Humans and other animals eat plants to obtain the energy stored there in order to build our bodies, move, and do other forms of work. And we use energy stored in coal, oil, and other fuels to heat our homes, power our devices, and move our vehicles.

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Section 7.1 Our Current Energy System

This section is designed to provide you with an overview of how our energy system works. Understanding the forms energy takes in our everyday lives is important as you consider how we might transition to a new energy economy.

Key Concepts We can classify energy a number of different ways. Primary energy is the energy stored in natural resources such as coal and wind. Primary energy typically must be converted into a form more useful to us—a process known as energy conversion. For example, the primary energy contained in a ton of coal is used in an electric power plant to boil water and produce steam, which spins a turbine that produces electricity. In this case, the electricity produced is known as secondary energy—a form of energy that is more convenient for us to use. Like- wise, the energy contained in a gallon of gasoline can be converted to kinetic energy in an automobile. We ultimately use energy to achieve an “end use” such as lighting for our homes or movement of our cars.

Recall from Chapter 2 that the second law of thermodynamics holds that no energy conver- sion is 100% efficient and that in every energy transformation, some energy is lost as heat. For example, when coal is burned in a power plant to produce electricity, roughly 70% of the chemical energy available in that coal is lost to heat, while only 30% is converted into an electric current. Likewise, when that electricity reaches your home or apartment and is trans- formed into light energy in an incandescent lightbulb, as much as 95% of the electric current is converted to heat, while only 5% or less is used to produce visible light. The term energy conversion efficiency describes the percentage of primary energy converted to secondary form—30% in the case of coal in an electric power plant. The term energy end-use effi- ciency describes the percentage of primary energy used in its final destination. In the case of burning coal to produce electricity to power an incandescent lightbulb, the energy end-use efficiency can be as low as 1% to 2% overall (see Figure 7.1).

Figure 7.1: Energy conversion

Only 2% of the energy available in coal is used to power an incandescent lightbulb because so much energy is lost in the process.

100 energy units in coal at start

62 units lost at power plant

2 units lost in transmission

34 units lost in heat

2 energy units used for illumination

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Section 7.1 Our Current Energy System

Primary energy sources can be further broken down into categories of nonrenewable or renewable. Nonrenewable energy sources are just what they sound like; energy sources that, once consumed, are no longer available for future use. Nonrenewable energy sources include the three main types of fossil fuels—coal, oil, and natural gas—as well as nuclear. As we’ll discuss, fossil fuels were formed by geological processes that took millions of years, so once we use them, they are essentially gone forever. Nuclear energy is produced using ura- nium, another resource that exists in limited supply. Compare that with renewable energy sources like solar and wind. Using sunlight to generate electricity through a solar panel, or wind to generate electricity through a spinning turbine, does not deplete those resources. However, we can only make use of these renewable energy sources when they are available. For this reason, energy experts often refer to nonrenewable energy sources as being “stock limited” and renewable energy sources like solar and wind as being “flow limited.”

Global Energy Consumption For most of human history, the primary sources of energy were sunlight, muscle power, and firewood. The ability to do work was limited by the number of hands available. With the agricultural revolution and the domestication of animals, activities like plowing and pull- ing wagons could be accomplished with animal power. Technological innovations gradually introduced ways to use energy from moving water (waterwheels) or wind (windmills) to mill grain or pump water. And throughout most of human history, we have burned firewood, crop residues, and dried animal dung for cooking, heating, and lighting.

The ways in which we use energy, as well as the types and quantities of energy used, began to change dramatically in the second half of the 18th century. The single most important rea- son for this change was the development of the steam engine. Steam engines could be used to move ships, trains, farm equipment, and factory machinery. Initially, steam engines were powered by firewood, but in major areas of demand this resulted in overcutting of forests and eventually wood shortages. In response, coal began to be exploited as an energy source, and by the late 19th century it became the dominant form of energy worldwide.

Coal remained the number one source of energy in the world until around 1950, when oil took over the number one spot. Oil was easier to extract and was much easier and cleaner to use, so many homes and businesses began to prefer oil to coal. Nevertheless, coal remains to this day the second most important global source of energy, and it is particularly important for industrial uses and electric power production. Since the late 20th century, natural gas has grown in importance and is projected to surpass coal in the near future to become the second most important energy source. Natural gas is a cleaner burning fuel than coal and is relatively easier to extract, transport, and utilize. As a result, many electric power companies have been shifting from coal to natural gas for electricity production. Renewable energy sources like hydropower, geothermal energy, solar energy, wind power, and biomass energy are currently the fourth most important form of energy worldwide, although these energy sources are also witnessing the fastest growth. Finally, nuclear energy—used almost exclusively for electric power production—is the fifth most important form of energy worldwide.

In addition to the EIA’s report, BP (2019) also publishes an annual Statistical Review of World Energy. BP reports global energy production and consumption in millions of tonnes of oil equivalent (Mtoe), rather than in quads. BP estimates global energy consumption in 2017

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Section 7.1 Our Current Energy System

was 13,511 Mtoe, up from 11,588 Mtoe 10 years earlier. Of that 13,511 Mtoe of consumption, nonrenewable fossil fuels are currently meeting about 85% of global energy demand. At the same time, the nonrenewable share of global energy supply is slowly declining over time. Oil, coal, and natural gas combined for 95% of global commercial energy demand in the late 1960s, 90% in the late 1980s, and 88% in 2008. Recent declines in the share of global energy from nonrenewable sources, while small, can be entirely accounted for by increases in the use of renewable energy sources like wind and solar.

If we look at global energy use on an individual, or per capita, basis, we can observe large differences in both the amounts and types of energy used in different countries around the world. The World Bank reports per capita energy use by country in kilograms of oil equiva- lent (kgoe). For 2013, the last year the World Bank published estimates, per capita energy consumption varied from as low as 215 kgoe per person per year in Bangladesh to as much as 7,202 kgoe per capita in Canada. Developing countries like Ghana, Haiti, and the Philippines had per capita energy consumption rates from 343 to 457 kgoe, while energy use in more developed countries like France, Germany, and Japan averaged around 3,700 kgoe per person per year. And whereas China is now the world’s largest consumer of energy, with the United States second, per capita rates of energy use in China (2,226 kgoe) are only one third of those in the United States (6,916 kgoe; World Bank, 2014).

Energy Sources and Uses Unlike our use of drinking water, seafood, fruits, vegetables, or meat discussed in recent chap- ters, we don’t really “demand” energy resources directly. We do not wake up in the morning and decide that we really need a ton of coal or pick up a barrel of oil on the way home from work. Instead, what we want from energy resources are the services they provide—heat, mobility, and electricity for lighting and powering our devices. These are known as energy end uses. Broadly speaking, we can break our nation’s energy consumption into four major end-use categories: transportation, industrial uses, residential uses, and commercial uses. We can also consider electric power generation as a major end use for energy resources, although in this case it actually represents a transformation of energy from one form to another.

It turns out that certain types of energy resources are better adapted or better matched to specific energy end uses than others. For example, coal may be the second most important energy resource worldwide, but it makes essentially no contribution to meeting our trans- portation needs. Likewise, oil or petroleum may be the single most important energy source globally, but—at least, in the United States—it makes almost no contribution to electric power generation. Understanding the connection between energy sources and uses is important if we are to avoid misunderstandings about appropriate energy policy. During the oil crises of the 1970s, when a global oil embargo severely reduced the supply of oil to the United States, the nuclear power industry launched an advertising campaign arguing for increased nuclear power production as a way to reduce dependence on imported oil. However, since our trans- portation system at the time, and even today, depended almost entirely on oil rather than electricity, increased nuclear power production would have had essentially no impact on oil import levels.

Perhaps one of the best ways to understand energy sources and uses, as well as levels of overall energy use in our economy, is to examine what’s known as an energy flow chart. In

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Section 7.1 Our Current Energy System

the United States the Lawrence Livermore National Laboratory (LLNL) produces the most detailed and informative energy flow charts. For our purposes, we will discuss the chart the LLNL published in 2018, which you can view at the following link: https://flowcharts.llnl .gov/content/assets/docs/2018_United-States_Energy.pdf. A more recent energy flow chart may be available at https://flowcharts.llnl.gov.

The left side of the LLNL energy flow chart shows the major energy sources used in the United States in 2018, such as petroleum, natural gas, and hydroelectric power. The number below each listed energy source represents the total amount consumed, measured in quads, and corresponds to the width of the line flowing out from each box to the right. For example, the light blue natural gas line is more than twice as wide as the black coal line because natural gas was used more than twice as much as coal was. Added together, all these energy sources totaled 101.2 quads of energy consumption in the United States, or about one sixth (17%) of global energy consumption for that year.

The boxes those lines flow toward indicate how certain energy sources are matched with specific energy end uses. For example, in the United States petroleum is predominantly used for industry and transportation, and the width of the dark green lines tell us that petroleum is first and foremost a source of energy for transportation. Likewise, coal, nuclear, hydro, and wind are almost entirely utilized to produce electricity. That electricity is then utilized in the residential, commercial, and industrial sectors, with virtually no electricity going to the trans- portation sector. Natural gas appears to be a more versatile energy source, with significant uses in electric power production, industrial purposes, residential home heating, and com- mercial applications.

The LLNL energy flow chart shows us that not all energy sources are created equal. As we consider our energy future, we must recognize that we cannot simply stop using petroleum overnight and power our trucks and cars with coal, wind, or nuclear power. We could do this over time if we changed the way we build cars and trucks and shift to electric engines, but such a transition takes time.

The LLNL energy flow chart also clarifies just how much energy is lost during energy conver- sions, which is referred to as rejected energy (light gray lines and boxes). For example, of the 38.2 quads of energy that are utilized to generate electricity, fully 25.3 quads (66.2%) are lost as rejected energy, mainly in the form of heat. Likewise, of the 28.3 quads of energy from petroleum and small amounts of ethanol and natural gas used in the transportation sector, 22.4 quads (79%) are lost as rejected energy. Overall, 68.5 of the 101.2 quads (67.7%) of energy used in the United States in 2018 were lost as rejected energy, with only 32.7 quads delivering actual energy services of mobility, heat, lighting and other applications.

There is growing consensus that the United States and the rest of the world need to undergo a rapid energy transition, moving away from an overwhelming reliance on nonrenewable fos- sil fuels to a world powered primarily by cleaner renewable energy resources. Such an energy transition is already under way, and we will discuss the opportunities and challenges later in the chapter. At this point, simply remember that planning this energy transition involves care- ful consideration of available energy sources and uses. For example, 95% of the 28.3 quads of energy currently used in the U.S. transportation sector comes from either petroleum or natural gas. To successfully and quickly transition away from these nonrenewable fossil fuels, what are our options?

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https://flowcharts.llnl.gov/content/assets/docs/2018_United-States_Energy.pdf
https://flowcharts.llnl.gov/content/assets/docs/2018_United-States_Energy.pdf
https://flowcharts.llnl.gov
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Section 7.1 Our Current Energy System

One possible approach is to shift to liquid fuels derived from biomass, such as ethanol from corn. Biofuels like ethanol currently meet about 10% of transportation energy needs in the United States, so this is something of a proven technology. However, as we’ll discuss, increas- ing corn production to produce more biofuels generates a different set of environmental impacts that may actually be worse than continuing to rely on petroleum.

A second option for transitioning away from fossil fuels in the transportation sector is to move toward electric cars and trucks. When in use, electric vehicles (EVs) emit no air pollution or greenhouse gas emissions, and so they would seem to be an ideal way to transition from non- renewable fossil fuels to a clean energy future. However, the actual impact of a transition to an EV fleet will depend to a large extent on how we generate the electricity used to charge these vehicles. Considering that we currently depend on coal for 34% of electric power production in the United States and natural gas for another 26% of our electricity, transitioning to EVs would have only a limited impact on efforts to reduce our dependence on nonrenewable fossil fuels and reduce greenhouse gas emissions. Furthermore, shifting from an oil-based trans- portation system to one that is powered by electricity would require significant investments in new infrastructure that would take time to put in place.

Achieving a clean energy transition in the transportation sector thus depends on accomplishing two large-scale changes in terms of energy sources and uses. First, we need to continue to increase the percent- age of electric power produced by clean energy sources like solar and wind. Second, we need to undertake a fundamental shift away from a vehicle fleet built on the inter- nal combustion engine to one powered by electric motors. The first of these changes appears to be well under way. The per- centage of U.S. electric power production coming from solar, wind, hydro and other renewable energy sources doubled from 9% in 2008 to 18% in 2018 (EIA, n.d.). In terms of the second change—a large-scale shift from internal combustion to EVs—there is disagreement among energy experts as to how or when this will happen. Some experts pre- dict that we are on the verge of a large-scale changeover and that rapid growth in demand for EVs in places like China will prompt U.S. automakers to speed up their production and distribution of these vehicles in the United States as well. However, other experts are more skeptical and point to infrastructure challenges such as a lack of charging facilities as a key barrier to rapid adoption of EVs.

The important point to make at this stage is to reemphasize that energy sources and uses are not easily interchangeable. Earlier energy transitions—from wood to coal in the 18th and 19th centuries and from coal to oil in the 20th century—involved numerous changes in the ways we produced and utilized energy. Likewise, transitioning away from nonrenewable coal, oil, and natural gas to renewable energy sources will also require changes in the ways we convert, store, and utilize that energy. An important factor in determining how fast such an energy transition can occur will be energy policy and how energy prices are determined and

Sven Loeffler/iStock/Getty Images Plus Transitioning fully to electric cars would take time, since infrastructure is still a challenge. The overall environmental impact would ultimately depend on how we generate the electricity used to charge these vehicles.

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Section 7.2 The Cost of Fossil Fuels

set. We’ll consider those factors in more detail in section 7.13. The next section takes a closer look at the fossil fuels that currently dominate our energy economy, including an examination of their origin, extraction, end use, environmental impacts, and future potential.

7.2 The Cost of Fossil Fuels

Coal, oil, and natural gas are known as fossil fuels because they were formed from the remains of organisms that lived 100 million to 500 million years ago. During that period, large areas of the planet were covered in freshwater swamps and shallow oceans that supported an abun- dance of plant life and phytoplankton. This plant life and phytoplankton utilized solar energy through photosynthesis to convert carbon dioxide and water into organic carbons.

Because these environments were so productive, organic material from dead plants, phyto- plankton, and other dead organisms accumulated more quickly than they could be broken down by decomposers. Thick layers of organic material accumulated at the bottom of these bodies of water and built up over time. Gradually, this organic material was covered by layers of sediment, further impeding any decomposition. Over millions of years, as sediment layers covering this organic material became thicker and thicker, a tremendous amount of weight, pressure, and heat were applied, producing coal, oil, or natural gas, depending on conditions and the organic source material. In a somewhat ironic twist, you could say that fossil fuels are an ancient form of solar energy, since they originated from plant material and living organ- isms formed through photosynthesis.

Even though there are many different terms and categories used to classify fossil fuel depos- its, geologists focus on two primary breakdowns. The first has to do with how concentrated and accessible a fossil fuel deposit is. Geologists use the concept of a resource pyramid to express this. Highly concentrated and easily accessible fossil fuels make up the top of the pyramid. These are the fuels that energy companies exploit first because they have the lowest production costs, such as oil deposits that gush from the ground or high-quality coal deposits close to the surface. When these deposits have been exhausted—as most have been—energy companies have to move down the resource pyramid to deposits that are more numerous but also more difficult to develop. These deposits are less concentrated, are more remote and harder to access, and require more effort to develop, such as offshore oil or deep coal depos- its. Further yet down the resource pyramid are fossil fuel deposits that are of such low con- centrations and/or in such difficult-to-reach locations that it would not make any economic sense to extract them unless energy prices were to go much higher.

This is also why geologists and energy experts point to the fact that we won’t really run out of fossil fuels, since there will always be some deposits that are simply not worth the effort to extract. It also highlights a concept known as energy return on investment (EROI), or the amount of useful energy extracted from a resource divided by the amount of energy it took to produce that energy. Energy deposits at the top of the resource pyramid have a high EROI since they produce a lot more energy than the energy needed to extract them. Further down the resource pyramid, the EROI number declines, until we reach an EROI of 1:1, where the amount of energy extracted is equal to the amount of energy used to extract it. Such a situ- ation makes little sense, and so energy companies would probably abandon a deposit long

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Section 7.3 Coal

before that point. In the United States the EROI for oil and gas production has declined from 30:1 in the 1960s to about 10:1 today (Guilford, Hall, O’Connor, & Cleveland, 2011).

The second category of difference for classifying fossil fuels (especially oil and gas) involves whether a particular deposit is conventional or unconventional. Historically, we have exploited conventional deposits of oil and gas found in porous rock formations. Traditional drilling techniques are used to bring oil and gas from these deposits to the surface. However, geologists have long been aware of oil and gas found in unconventional deposits, such as oil-soaked sands or shale formations that have trapped gas. As we’ll discuss, these uncon- ventional deposits are more difficult to exploit, and extraction typically results in more seri- ous environmental impacts. But because most of the productive conventional deposits have already been heavily exploited, unconventional deposits are now the focus of much more attention than they were in the past. The move from conventional to unconventional deposits also helps explain the declining EROI figure for oil and gas production, since the latter require more energy and effort to exploit.

Another concept common to the use of fossil fuels is that of external costs or externalities. An external cost is a cost associated with the use of a product that is not reflected in the price we actually pay for that product. For example, when coal is mined and burned to produce electricity, it can have a number of environmental impacts. Coal mining can harm water quality, and coal burning can create air pollution. If poor water quality or air pollution make someone sick, the cost of treating that illness is usually not factored into the price for that coal or the electricity it was used to produce. Those health care costs are external costs, and they represent a hidden cost to the use of fossil fuel energy resources because they mask or hide the true costs associated with actually using that resource.

The next sections will take a closer look at each of the three main fossil fuels and consider issues related to their production, use, environmental impacts, and future.

7.3 Coal

Most of the coal we use today originates from swampy forests of 300 million to 400 million years ago. Over millions of years vegetation in these swamps fell to the ground and accumu- lated in layers faster than it could decompose. Swampy conditions limited oxygen supply and resulted in partial, anaerobic decomposition, producing a material known as peat. As peat was buried under more and more layers of sediment, it pressed out most of the water and

ping han/iStock/Thinkstock Conventional deposits can be more easily accessed and brought to the surface using conventional drilling techniques, like those pictured. Unconventional deposits require more energy to extract and have lower EROI.