Key Concepts

After completing this chapter, you will be able to:

1. Describe the global and U.S. production and use of metals, fossil fuels, and other non-renewable resources.
2. Explain the heavy reliance of industrialized economies on non-renewable resources, and predict whether these essential sources of materials and energy will continue to be readily available into the foreseeable future.
3. Outline major sources of energy that are available for use in industrialized countries, and describe the potential roles of these in a sustainable economy.

Introduction

As we noted in Chapter 11, the reserves of non-renewable resources are inexorably diminished as they are extracted from the environment and used in the human economy. This is because non-renewable resources are finite in quantity and their stocks do not regenerate after they are mined. Note that the word reserve has a specific meaning here – it is used to denote a known amount of material that can be economically recovered from the environment (that is, while making a profit).

Of course, continuing exploration may discover previously unknown deposits of non-renewable resources. If that happens, there is an increase in the known reserves of the resource. There are, however, limits to the number of “new” discoveries of non-renewable resources that can be made on planet Earth (Image 18.1).

Image 18.1. Offshore Drilling Catastrophe. Continued exploration for non-renewable resources can discover new reserves. Because Earth is finite, however, there are limits to these discoveries, which are being approached rapidly. This enormous off-shore production platform burst into flames off the southeast coast of Louisiana. This rig, named Deep Water Horizon, is infamous for its devastating 2010 oil spill into the Gulf of Mexico while being leased by British Petroleum (BP). It inevitably sank 36 hours after catching fire, leaving an uncapped oil well spilling for months. Source:  “Deepwater Horizon Fire” by EPI2oh is licensed under CC BY-ND 2.0.

Changes in the value of non-renewable commodities also affect the sizes of their economically recoverable reserves. For example, if the value of gold increases in its marketplace, then it may become profitable to prospect for new stocks in remote places, to mine lower-grade ores, and to reprocess “waste” materials containing small quantities of this valuable metal. An improvement of technology may have the same effect, for instance, by making it profitable to process ore mines that were previously non-economic.

In addition, the life cycle in the economy of some non-renewable resources, particularly metals, can be extended by recycling. This process involves collecting and processing disused industrial and household products to recover reusable materials, such as metals and plastics. However, there are thermodynamic and economic limits to recycling, which means the process cannot be 100% efficient. Furthermore, the demand for non-renewable resources is increasing rapidly because of population growth, spreading industrialization, and improving standards of living along with the associated per-capita consumption. This has resulted in an accelerating demand for non-renewables that must be satisfied by mining additional quantities from the environment.

The most important classes of non-renewable resources are metals, fossil fuels, and certain other minerals such as gypsum and potash. The production and uses of these important natural resources are examined in the following sections.

Metals

Metals have a wide range of useful physical and chemical properties. They can be used as pure elemental substances, as alloys (mixtures) of various metals, and as compounds that also contain non-metals. Metals are used to manufacture tools, machines, and electricity-conducting wires; to construct buildings and other structures; and for many other purposes. The most prominent metals in industrial use are aluminum (Al), chromium (Cr), cobalt (Co), copper (Cu), iron (Fe), lead (Pb), manganese (Mn), mercury (Hg), nickel (Ni), tin (Sn), uranium (U), and zinc (Zn). The precious metals gold (Au), platinum (Pt), and silver (Ag) have some industrial uses (such as conductors in electronics), but are valued mostly for aesthetic reasons, particularly to manufacture jewelry. Some of the more common metal alloys are brass (containing at least 50% Cu, plus Zn), bronze (mostly Cu, plus Sn and sometimes Zn and Pb), and steel (mostly Fe, but also containing carbon, Cr, Mn, and/or Ni). Metals are mined from the environment, usually as minerals that also contain sulfur or oxygen. Deposits of metal-bearing minerals that are economically extractable contribute to the known reserves of metals. An ore is an assortment of minerals that are mined and processed to manufacture pure metals.

Ore extraction by mining is the initial step in the process of bringing metals into the material economy. This may be conducted in surface pits or strip mines, or in underground shaft-mines that may penetrate kilometers underground. In an industrial facility called a mill, the ore is crushed to a fine powder by heavy steel balls or rods within huge rotating tumblers. The ground ore is then separated into a metal-rich fraction and a waste known as tailings. Depending on the local geography, the waste tailings may be discarded onto a contained area on land, into a nearby lake, or into the ocean (see Chapter 22).

If the metal-rich fraction contains sulfide minerals, it is next concentrated in a smelter by roasting at high temperature in the presence of oxygen. This releases gaseous sulfur dioxide (SO₂) while leaving the metals behind. The concentrate from the smelter is later processed into pure metal in a facility called a refinery. The pure metal is then used to manufacture industrial and consumer products. The SO₂ may be processed into sulfur or sulfuric acid that can be used in various other industrial processes, or it may be released to the environment as a pollutant.

After the useful life of manufactured products has ended, they can be recycled back into the refining and manufacturing processes, or they may be discarded into a landfill.

High-quality ores are geologically uncommon. The deposits that are most economic for mining are typically located fairly close to the surface, and the ores have a relatively high concentration of metals. However, the thresholds vary depending on the value of the metal being processed. Ores with very small concentrations of gold and platinum can be economically mined because these metals are extremely valuable (per unit of weight). In contrast, less-valuable aluminum and iron must be mined as richer ores, in which the metals are present in high concentrations.

Data showing the global production of industrially important metals are given in Table 18.1. The life index (or production life) is calculated as the known reserves divided by the annual rate of production. It is important to remember that known reserves can increase from new discoveries, changes in technology, and more favorable economics for the resource. Additionally, reserves are defined as part of the reserve base which could be economically extracted or produced at the time of determination and are not the total estimation of the existing amount of that resource.

The U.S. is one of the world’s leading producers of metals, accounting for 0.05% of the global production of nickel in 2019, 1.7% of aluminum, and 6% zinc (Tables 18.1 and 18.2). Much metal production is intended for export. Domestic consumption is about 39% of the value of production of all metals (Table 18.2). Metal-ore mining contributed $28.59billion to the GDP of the U.S. in 2019, and a total of 0.13% of the GDP (NMA, 2021).

Table 18.1. Global Production and Reserves of Selected Metals. Some reserve records are not available due to widespread abundance or withheld for classification. Data from: U.S. Geological Survey (2020).

Metal	Production (metric tons)	Reserves (metric tons)	Life Index (years)
Aluminum	64 million	Not available	–
Cadmium	25,000	~750,000	30
Copper	20 million	870 million	43.5
Iron (ore)	2.5 billion	170 billion	68
Lead	4.5 million	90 million	20
Mercury	4,000	Not available	–
Nickel	2.7 million	89 million	32.9
Tin	310,000	47 million	15.2
Zinc	13 million	250 million	19.2
Steel (crude)	1.9 billion	Not available	–

Table 18.2. Reserves, Production, and Consumption of Selected Metals in the United States, 2019. Data from: and U.S. Geological Survey (2020).

Metal	Total Production (metric tons)	Consumption (metric tons)	Reserves	Life Index
Aluminum	1.1 million	3.4 million	1.79 million	1.63
Copper	2.3 million	3.2 million	51 million	22.2
Gold	530	150	3,000	5.66
Iron (ore)	48 million	37 million	3 million	0.063
Nickel	14,000	220,000	110,000	7.86
Sand and Gravel	970 million	980 million	Not available
Zinc	780,000	870,000	11 million	14.1

Fossil Fuels

Fossil fuels include coal, petroleum, natural gas, oil-sand, and oil-shale. These materials are derived from the partially decomposed biomass of dead plants and other organisms that lived hundreds of millions of years ago. The ancient biomass became entombed in marine sediment, which much later became deeply buried and eventually lithified into sedimentary rocks such as shale and sandstone. Deep within those geological formations, under conditions of high pressure, high temperature, and low oxygen, the organic matter transformed extremely slowly into hydrocarbons (molecules that are composed only of carbon and hydrogen) and other organic compounds. In some respects, fossil fuels can be considered to be a form of stockpiled solar energy – sunlight that was fixed by plants into organic matter and then stored geologically and then extracted from the environment (Image 18.2).

Image 18.2. Oil Pumps. Because petroleum and other fossil fuels are non-renewable resources, their future reserves are diminished when they are extracted from the environment. This is a field of oil pumps in California. Source: “California – Oil Pumps” by CGP Grey is licensed under CC BY 2.0.

In a geological sense, fossil fuels are still being produced today, by the same processes that involve dead biomass being subjected to high pressure and temperature. Because the natural geological production of fossil fuels continues, it might be argued that these materials are a kind of renewable resource. However, the rate at which fossil fuels are being extracted and used is enormously faster than their extremely slow regeneration. Under this circumstance, fossil fuels can only be regarded as being non-renewable.

Hydrocarbons are the most abundant chemicals in fossil fuels. However, many additional kinds of organic compounds may also be present, which incorporate sulfur, nitrogen, and other elements in their structure. Coal in particular is often contaminated with many inorganic minerals, such as shale and pyrite.

The most important use of fossil fuels is as a source of energy. They are combusted in vehicle engines, power plants, and other machines to produce the energy needed to perform work in industry, for transportation, and for household use. Fossil fuels are also used to produce energy to heat indoor spaces, an especially important function in countries with a seasonally cold climate. Another key use is for the manufacturing of synthetic materials, including almost all plastics. In addition, asphaltic materials are used to construct roads and to manufacture roofing shingles for buildings.

Coal is a solid material that can vary greatly in its chemical and physical qualities. The highest quality coals are anthracite and bituminous, which are hard, shiny, black minerals with a high energy density (the energy content per unit of weight). Lignite is a poorer grade of coal, and it is a softer, flaky material with a lower energy density. Coal is mined in various ways. If deposits occur close to the surface, they are typically extracted by strip-mining, which involves the use of huge shovels to uncover and collect the coal-bearing strata, which are then transported using immense trucks. Deeper deposits of coal are mined from underground shafts, which may follow a seam, kilometers into the ground. Most coal in North America is extracted by strip-mining.

After it is mined, coal may be washed to remove some of the impurities and then ground into a powder. Most is then combusted in a large industrial facility, such as a coal-fired generating station, a use that accounts for about half of the global use of coal and 24% of electricity in the U.S. (BP, 2019). In addition, about 75% of the world’s steel is manufactured using coal as an energy source, often as a concentrated material known as coke. Coal can also be used to manufacture synthetic petroleum.

Petroleum (crude oil) is a fluid mixture of hydrocarbons with some impurities, such as organic compounds that contain sulfur, nitrogen, and vanadium. Petroleum from different places varies greatly, from a heavy tarry material that must be heated before it will flow, to an extremely light fluid that quickly volatizes into the atmosphere. Petroleum is mined using drilled wells, from which the liquid mineral is forced to the surface by geological pressure. Often, the natural pressure is supplemented by pumping.

A heavy form of petroleum called bitumen is also produced by mining and refining oil- sand, which is extracted in northern Alberta, Canada. Oil-sand deposits that are close to the surface are mined in immense open pits, while deeper materials are treated with steam so they will flow and are then extracted as a heavy liquid using drilled wells (Image 18.3).

Image 18.3. Oil-sand Mining. View of an open-pit mine for the extraction of bitumen-sand in northern Alberta, Canada. Source: B. Freedman.

Oil-sand mining and processing are energy-intensive activities that take place in huge industrial facilities. The energy to run machinery and processing facilities is obtained by burning fossil fuels, particularly natural gas, so the industry is a major emitter of greenhouse gases. Deposits of oil-sand that occur near the surface (less than about 75 m deep) are mined in open pits (strip-mined). It is then processed using heat and steam to yield a viscous bitumen (its room-temperature consistency is similar to molasses). The bitumen is modified with light hydrocarbon fluids to reduce its viscosity so that it can flow and be transported in a pipeline. Ultimately, about 20% of the total oil-sand resource lies close enough to the surface to potentially be extracted by open-pit mining. About two-thirds of the recent production of oil-sand bitumen is from surface mines. The other one-third of oil-sand bitumen production is from in situ (“in place”) extraction of deposits deeper than 75 m. This is done in various ways, such as injecting steam into the deposit and then pumping the liquefied bitumen to the surface for further processing.

Despite oil sands not being quite as integral to the energy culture of the U.S. as Canada, they can still be found as the South Dakota Tar Sands, as well as in Utah. There are additional important environmental effects of the mining and processing of oil sands. These include pollution of the atmosphere, groundwater, and surface water; the extensive destruction of natural habitats; and socio-economic disruptions of rural and Aboriginal communities

Once extracted, petroleum is transported by overland pipelines, trucks, trains, and ships to an industrial facility known as a refinery, where the crude material is separated into various constituents. The fractions may be used as a liquid fuel, or they can be manufactured into many useful materials, such as plastics and pigments. The refined fractions include the following:

• A light hydrocarbon mixture known as gasoline, which is used to fuel automobiles
• Slightly heavier fractions, such as diesel fuel used by trucks and trains and a home-heating fuel
• Kerosene, which is used for heating and cooking and as a fuel for airplanes
• Dense residual oils, which are used as a fuel in oil-fired power plants and in large ships
• Semi-solid asphalts that are used to pave roads and manufacture roofing products

Natural gas is also extracted using drilled wells. The dominant hydrocarbon in natural gas is methane, but ethane, propane, and butane are also present, as often is hydrogen sulfide. Most natural gas is transported in steel pipelines from the well sites to distant markets. Sometimes it is liquefied under pressure for transportation, particularly by ships. In the U.S. it is distributed mostly through an extensive network of pipelines. Natural gas is used to generate electricity, to heat buildings, to cook food, to power light vehicles, and to manufacture nitrogen fertilizer.

Production, Reserves, and Consumption

The global production and reserves of fossil fuels are shown in Table 18.3. The production of petroleum increased by 40% between 1993 and 2019, natural gas by 97%, and coal by 88%. There is active exploration for all these fuels, and additional reserves are being discovered in various regions of the world. Fossil fuels are, however, being consumed extremely rapidly, particularly in developed and rapidly developing economies. Consequently, the expected lifetimes of the known reserves are alarmingly short, equivalent to 114 years for coal, 53 years for natural gas, and 51 years for petroleum.

These numbers should not be interpreted too literally, however, because ongoing exploration is discovering additional deposits, which add to the known reserves. This is illustrated by changes in the calculated reserve life of petroleum, which was 46 years in 1993, but twenty years later had actually increased to 58 years. Of course, this seemingly unexpected result is due to the fact that previously unknown reserves of petroleum had been discovered during that 20-year period, or rising prices had made once-uneconomic resources viable (such as the oil-sands of Alberta). Nevertheless, the discoveries will be limited by the finite amounts present on Earth, so the fact remains that the stocks of these non-renewable resources are being depleted rapidly.

Table 18.3. Global Production and Reserves of Fossil Fuels, 2019. Reserves are the total amounts of a resource that are known to exist. The reserve life is the reserves divided by the annual rate of extraction. Source: Data from British Petroleum (2019).

Fossil Fuel	Reserves	Production (TWh)	Reserve Life (years)
Coal	1.07 trillion tonnes	52,155	114
Petroleum	1.74 trillion barrels	46,549	52.8
Natural Gas	197 trillion m3	39,893	50.7

At the present time, petroleum is the world’s most important fossil fuel resource, largely because it can easily be refined into portable liquid fuels that are readily used as a source of energy for many industrial and domestic purposes. In addition, petroleum is the major feedstock used to manufacture plastics and other synthetic materials.

About 46% of the world’s proven recoverable reserves of petroleum occurs in the Middle East. This fact underscores the strategic importance of that region to the global energy economy and its security. Saudi Arabia alone has 16% of the world’s petroleum reserves, followed by Iraq, Iran, and Kuwait each with 6-9%. The large reserves cited for Venezuela and Canada are largely for “non-conventional” sources of petroleum, such as very-heavy oil and oil-sand (respectively), which are relatively expensive to mine and refine. The world’s most developed economies are in Europe, North America, and eastern Asia. Those in Europe and Asia depend heavily on petroleum imports from the Middle East, Russia, and Venezuela to maintain their consumption levels. This was once also the case for North America, but it has been much less so since about 2010 because of large increases in domestic production associated with petroleum in shale formations and oil-sand in northern Alberta.

The world’s best-endowed countries in terms of total fossil-fuel resources are Russia and the U.S., both of which have enormous reserves of natural gas, coal, and petroleum (Table 18.4).

Table 18.4. Reserves of Fossil Fuels in Selected Countries. The countries are listed in order of decreasing reserves of petroleum in 2018. Data are proven reserves, and are from British Petroleum (2019).

Country	Petroleum (barrels)	Coal (tonnes)	Natural Gas (m3)
Venezuela	303.81 billion	731 million	6.30 trillion
Saudi Arabia	297.67 billion	–	5.89 trillion
Canada	170.77 billion	6.58 billion	1.91 trillion
Russia	107.21 billion	162.17 billion	38.04 trillion
China	26.19 billion	141.59 billion	6.36 trillion
Australia	2.39 billion	149.08 billion	2.39 trillion

The production lives of proven recoverable U.S. reserves of fossil fuels are shown in Table 18.5. Remember, however, that the amount of the reserves is affected by new discoveries, the advent of technologies that make previously unrecoverable stocks economically viable, as well as increases in commodity prices that make it profitable to utilize once-marginal resources. In the U.S., this has recently been the case of natural gas. In the past 10 years, natural gas production in the U.S. has increased by 65%.

Table 18.5. Production, Consumption, and Reserves of Fossil Fuels in the U.S., 2019. Percentage consumption refers to the fraction of U.S. production that is used within the U.S. Source: Data from British Petroleum (2019).

Fossil Fuel	Production (TWh)	Consumption (TWh)	% Consumption	Reserves
Petroleum	52,155	10,274	46.93	68.89 billion barrels
Gas	39,893	8,466	38.68	12.87 trillion m3
Coal	46,549	3,150	14.39	249.54 billion tonnes

The U.S. petroleum independence has increased over recent years where now 93% of petroleum consumption is domestically produced. As of 2019, 19.25 million barrels per day were produced while 20.46 million barrels were consumed per day. With increased petroleum production, exports have increased as well. On average 9.1 million barrels a day were imported to the U.S., but this is almost entirely offset by 8.5 million barrels a day that are exported (U.S. EIA, 2020).

Other Minerals

Other materials that are mined in large quantities in North America include asbestos, diamonds, gypsum, limestone, potash, salt, sulfur, aggregates, and peat. Except for diamonds, these materials have a smaller commodity value (value per tonne) than metals and fossil fuels. Global shortages of these materials are not imminent. The mining of nonfuel minerals in the U.S. had a value of $86.3 billion in 2019 (USGS, 2020).

Asbestos refers to a group of tough, fibrous, incombustible silicate minerals that are used to manufacture fireproof insulation, cement additives, brake linings, and many other products. However, certain kinds of asbestos minerals have been linked to human health problems, particularly lung diseases. The U.S. ceased asbestos production in 2002. As a result of domestic decline with concerns relating to health, the U.S. now depends on international imports for manufacturing purposes. In 2019 the U.S. imported 100 metric tons, 96 of which from Brazil, and 4 metric tons from Russia.

Diamonds are mostly imported into the U.S. There is only one producing diamond mine in the U.S.: Jastro Winkle Alluvial Diamond Field in California. Two other mines that previously produced have been shut down, one in 1976 in Arkansas, and one in 2001 in Colorado. The U.S. imports 840,000 of carats.

Gypsum, a mineral composed of calcium sulfate, is used to manufacture plaster and wallboard for the construction industry. In 2019, domestic production of crude gypsum was estimated to be 20 million tons with a value of about $160 million. Top producing states include Nevada, Kansas, Oklahoma, and Texas.

Lime is a calcium-containing inorganic mineral, commonly found in the form of limestone (calcium carbonate). It is used to manufacture cement, as well as lime for making plaster. In addition, some limestone, and the related metamorphic rock known as marble, is quarried for use as building stone and facings. In the U.S. about 18 million metric tons of limestone were mined in 2019 valued at $2.4 billion. Globally, 430 million metric tons of lime is produced.

Potash is a rock formed from the mineral potash feldspar, and it is mined to manufacture potassium-containing fertilizer. Even though the U.S. potash production was valued at $400 million for 510,000 metric tons in 2019, the country imports 5 million metric tons annually. Eighty-five percent of industry sales is from the fertilizer industry for agriculture.

Salt, or sodium chloride, is used in the chemical manufacturing industry, for de-icing roads, as “table salt,” and as a food additive and flavoring. In 2019, domestic production increased to 42 million metric tons estimated at a $2.3 billion value. High producing states include Utah, Texas, Michigan, and Ohio.

Sulfur is manufactured from hydrogen sulfide obtained from sour-gas wells (gas wells rich in H₂S), from pollution-control scrubbers (for SO₂) at metal smelters, and from deposits of native (or elemental) sulfur. Sulfur is used in the chemical manufacturing industries and to make fertilizer. About 8.2 million metric tons of elemental sulfur were produced in 2019, with a value of $440 million. About 55% of the domestic sulfur production is obtained from sour-gas wells in Louisiana and Texas.

Aggregates include sand, gravel, and other materials that are mined for use in road construction and as fillers for concrete in the construction industry. Aggregates are a low-grade resource, having relatively little value per unit. About 970 million metric tons were quarried in 2019, with a value of $9 billion. These materials are mined in all of the states but the largest producers include Texas, California, and Arizona among others.

Peat is a sub-fossil material that has developed from dead plant biomass that is hundreds to thousands of years old. It accumulates in bog wetlands, where it becomes partially decomposed (or humified). Peat is sometimes dried and burned as a source of energy, an important use in Ireland, parts of northern Europe, and Russia. In the U.S., however, peat is mined for use as a horticultural material and to produce absorbent hygienic products such as diapers and sanitary napkins. About 470,000 metric tonnes of peat were mined in 2019, with a value of $14 million. Most peat mining occurs in Florida, Michigan, and Minnesota.

Energy Use

It is critical for any economy to have ready access to relatively inexpensive and accessible sources of energy for commercial, industrial, and household purposes. The use of large amounts of energy is especially characteristic of developed countries, such as the U.S. Relatively wealthy, developed countries use much more energy (on a per-capita basis) than do poorer, less-developed countries.

Ever since people achieved a mastery of fire, they have used fuels for subsistence purposes, that is, to cook food and to keep warm. Initially, locally collected wood and other plant biomass were the fuels used for those purposes. Perhaps only one-million people were alive when fire was first domesticated, and their per-capita energy use was small. Consequently, biomass fuels were a renewable source of energy because the rate at which they were being harvested was much smaller than the rate at which new biomass was being produced by vegetation.

In modern times, however, the human population is enormously larger than it was when fire was first put to work. Moreover, many countries now have intensely industrialized economies in which per-capita energy usage is extremely high. The combination of population growth and increased per-capita energy use means that enormous amounts of energy are used in developed countries. The energy is needed to fuel industrial processes, to manufacture and run machines, to keep warm in winter and cool in summer, and to prepare food.

Most industrial energy supplies are based on the use of non-renewable resources, although certain renewable sources may also be important. For comprehensiveness, both non-renewable and renewable energy sources are discussed together in this section.

Sources of Energy

The world’s major sources of industrial energy are fossil fuels and nuclear fuels, both of which are non-renewable (Image 18.5). Hydroelectric power, generated using the renewable energy of flowing water, is also important in some regions, including parts of the U.S. Relatively minor energy sources, often called “alternative sources”, include biomass fuels, geothermal heat, solar power, wind, and waves, all of which are potentially renewable.

Any of the above sources can be harnessed to drive a turbine, which spins an electrical generator that converts the kinetic energy of motion into electrical energy. Solar energy can also generate electricity more directly, through photovoltaic technology (see below). Electricity is one of the most important kinds of energy used in industrial societies, being widely distributed to industries and homes through a network of transmission lines. The following sections briefly describe how these various energy sources are used.

Image 18.5. Indian Point Nuclear Power Plant. Electricity generated by using nuclear fuel or by burning coal, oil, or natural gas uses non-renewable sources of energy. This is a photo of the Indian Point Nuclear Power Plant, situated on the east bank of the Hudson River. The plant closed in 2021 due to environmental concerns. Source: “Indian Point Nuclear Power Plant” by Tony Fischer Photography is licensed under CC BY 2.0.

Fossil Fuels

Coal, natural gas, petroleum, and their refined products can be combusted in power plants, where the potential energy of the fuel is harnessed to generate electricity. Fossil fuels can also power machines directly, particularly in transportation, in which gasoline, diesel, liquefied natural gas, and other “portable” fuels are used in automobiles, trucks, airplanes, trains, and ships. Fossil fuels are also combusted in the furnaces of many homes and larger buildings to provide warmth during colder times of the year. The burning of fossil fuels has many environmental drawbacks, including emissions of greenhouse gases, sulfur dioxide, and other pollutants into the atmosphere.

Nuclear Fuels

Nuclear fuels contain unstable isotopes of the heavy elements uranium and plutonium (235U and 239Pu, respectively). These can decay through a process known as fission, which produces lighter elements while releasing 2-3 neutrons per nucleus and an enormous quantity of energy. The emitted neutrons may be absorbed by other atoms of 235U or 239Pu, causing them to also become unstable and undergo fission in a process known as a chain reaction. An uncontrolled chain reaction can result in a devastating nuclear explosion. In a nuclear reactor, however, the flux of neutrons is carefully regulated, which allows electricity to be produced safely and continuously.

Nuclear reactions are fundamentally different from chemical reactions, in which atoms recombine into different compounds without changing their internal structure. In nuclear fission, the atomic structure is fundamentally altered, and small amounts of matter are transformed into immense quantities of energy.

Most of the energy liberated by nuclear fission is released as heat. In a nuclear power plant, some of the heat is used to boil water. The resulting steam drives a turbine, which generates electricity. Most nuclear-fueled power plants are huge commercial reactors that produce electricity for industrial and residential use in large urban areas (Image 18.5). Smaller reactors are sometimes used to power military ships and submarines, or for research. ²³⁵U is the fuel that is used in conventional nuclear reactors, including those in the U.S. ²³⁵U is obtained from uranium ore, which is mined in various places in the world. Uranium produced by refining ore typically consists of about 99.3% non-fissile ²³⁸U and only 0.7% ²³⁵U. Most commercial reactors require a fuel that has been further refined to enrich the ²³⁵U concentration to about 3%.

Various elements, most of which are also radioactive (such as radon gas), are produced during fission reactions. One of these, ²³⁹Pu, can also be used as a component of nuclear fuel in power plants. To obtain ²³⁹Pu for this purpose (or for use in manufacturing nuclear weapons), spent fuel from nuclear generating stations is reprocessed. Other trans-uranium elements and any remaining ²³⁵U (as well as non-fissile ²³⁸U) can also be recovered and be used to manufacture new fuel for reactors.

So-called fast-breeder reactors are designed to optimize the production of ²³⁹Pu (which occurs when an atom of ²³⁸U absorbs a neutron to produce ²³⁹U, which then forms ²³⁹Pu by the emission of two beta electrons). Although fast-breeder reactors have been demonstrated, they have not been commercially developed. Breeder reactors produce “new” nuclear fuel (by producing plutonium) and thereby help to optimize use of the uranium resource. However, there are limits to the process because the original quantity of ²³⁸U is eventually depleted. Therefore, both ²³⁵U and ²³⁹Pu should be considered to be non-renewable resources.

A number of important environmental problems are associated with nuclear power. These include the small but real possibility of a catastrophic accident such as a meltdown of the reactor core, which can result in the release of large amounts of radioactive material into the environment (as happened at the Chernobyl reactor in Ukraine in 1986). Nuclear reactions also produce extremely toxic, long-lived radioactive by-products (such as plutonium), which must be safely managed for very long periods of time (up to tens of thousands of years). Enormous quantities of these “high-level” wastes are stockpiled in the U.S. and in other countries that use nuclear power, but so far there are no permanent solutions to the problem of their long-term management. Another problem is the emission of toxic radon gas and radioactivity from “low-level” wastes associated with uranium mines, structural elements of nuclear power plants, and other sources.

Fusion is another kind of energy-producing nuclear reaction. This process occurs when light nuclei are forced to combine under conditions of extremely high temperature (millions of degrees) and pressure, resulting in an enormous release of energy. Fusion usually involves the combining of hydrogen isotopes. One common fusion reaction involves two protons (two hydrogen nuclei, 1H) fusing to form a deuterium nucleus (composed of one proton and one neutron, 2H), while also emitting a beta electron and an extremely large amount of energy.

Fusion reactions occur naturally in the interior of the Sun and other stars, and they can also be initiated by exposing hydrogen to the enormous heat and pressure generated by a fission nuclear explosion, as occurs in a so-called hydrogen bomb. However, nuclear technologists have not yet designed a system that can control fusion reactions to the degree necessary to generate electricity in an economic system. If this technology is ever developed, it would be an enormous benefit to industrial society. It would mean that virtually unlimited supplies of hydrogen fuel for fusion reactors could be extracted from the oceans, which would essentially eliminate constraints on energy supply. So far, however, controlled fusion reactions remain the stuff of science fiction.

Hydroelectric Energy

Hydroelectric energy involves harnessing the kinetic energy of flowing water to drive a turbine that generates electricity. Because the energy of flowing water develops naturally through the hydrologic cycle, hydroelectricity is a renewable source of energy. There are two classes of technologies for the generation of hydroelectricity.

First, run-of-the-river hydroelectricity involves tapping the natural flow of a watercourse without developing a large up-river storage reservoir. Consequently, this electricity generation depends on the natural patterns of river flow and is highly seasonal. Second, reservoir-generated hydroelectricity involves the construction of a dam in a river to store a huge quantity of water in a lake-like waterbody. The reservoir accumulates part of the seasonal high flow so that the generation of electricity can occur relatively steadily throughout the year. There are more than 90,000 dams across the U.S., the highest production being Grand Coulee dam in the state of Washington that generates a sustained output of 6,809 megawatts. However, Grand Coulee, as well as many others in the Pacific Northwest, have ecological impacts such as hindering fish migrations, and negatively affecting the indigenous cultures dependent on them.

One of the U.S.’s most historic hydroelectric generating facilities is the Hoover Dam (Image 18.6), which holds back Lake Mead and is fed by the Colorado River on the border of Nevada and Arizona. It opened in 1936 and continues to serve not only as a tourist attraction but also with a production capacity of nearly 4 million megawatt-hours (MW-h) a year to supply Nevada, Arizona, and California. All of these facilities have large reservoirs to store water. Lake Mead behind the Hoover Dam, fittingly, is the largest reservoir in the U.S. when at full capacity. Although hydroelectric energy is renewable, important environmental impacts are associated with use of this technology. Changes in the amount and timing of water flow in rivers cause important ecological damages, as does the extensive flooding that occurs when a reservoir is developed (see Chapter 24).

Image 18.6. Hydroelectricity is a renewable source of energy. The Hoover Dam interrupts the Colorado River for energy production. Source: “Hoover Dam” by RalphArvesen is licensed under CC BY-NC 2.0.

Solar Energy

Solar energy is continuously available during the day, and it can be tapped in various ways as a renewable source of energy. For example, it is stored by plants as they grow, so that their biomass can be harvested and combusted to release its potential energy (see Biomass Energy, below).

Solar energy can also be trapped within a glass-enclosed space. This happens because glass is transparent to visible wavelengths of sunlight, but not to most of the infrared. This allows the use of passive solar or “greenhouse” designs to heat buildings. Solar energy can also be captured using black, highly absorptive surfaces to heat enclosed water or another fluid, which can then be distributed through piping to warm the interior of a building.

Solar energy can also be used to generate electricity using photovoltaic technology (solar cells), which converts electromagnetic energy directly into electricity. In another technology, large, extremely reflective parabolic mirrors are used to focus sunlight onto an enclosed volume that contains water or another fluid, which becomes heated and generates steam that is used to drive a turbine to generate electricity.

Geothermal Energy

Geothermal energy can be tapped in the very few places where magma occurs relatively close to the surface and heats ground water. The boiling-hot water can be piped to the surface, where its heat content is used to warm buildings or to generate electricity. In addition, the smaller energy content of slightly warmed geothermal water, which is present almost everywhere, can be accessed using heat-pump technology and used for space heating or to provide warm water for a manufacturing process. Geothermal energy is a renewable source as long as the supply of groundwater available to be heated within the ground is not depleted by excessive pumping.

Wind Energy

The kinetic energy of moving air masses, or wind energy, can be tapped and used in various ways. A sailboat uses wind energy to move through the water, a windmill may be used to power the lifting of groundwater for use at the surface, and wind turbines are designed to generate electricity. Extensive wind-farms, consisting of arrays of highly efficient wind-driven turbines, have been constructed to generate electricity in consistently windy places in many parts of the world (Image 18.7). In 2013, Alta Wind Energy Center (Mojave Wind Farm) was established as the largest wind farm in the U.S. in Kern County, California. With a capacity of 1,548 MW, it is also the third largest onshore wind farm in the world. Nationwide, the U.S. produces 303.1 TWh from wind power (NS Energy, 2018).

Image 18.7. Wind is increasingly being used as a source of commercial energy in the United States. This windfarm operates in Altamont Pass, California, an area known for having the greatest concentration of wind turbines in the world. Source: “Farming the wind: One of these is not like the other” by Images by John ‘K’ is licensed under CC BY-NC-ND 2.0.

Tidal Energy

Tidal cycles develop because of the gravitational attraction between Earth and the Moon. In a few coastal places, tidal energy, the kinetic energy of tidal flows, can be harnessed to drive turbines and generate electricity. While there are no commercial active tidal energy plants in the U.S., there are developmental projects underway in Maine, and an experimental demonstration runs on Roosevelt Island in New York.

Wave Energy

Waves on the ocean surface are another manifestation of kinetic energy. Wave energy can be harnessed using specially designed buoys that generate electricity as they bob up and down, although this technology has not yet been developed on a commercial scale.

Biomass Energy

The biomass of trees and other plants contains chemical potential energy. This biomass energy is actually solar energy that has been fixed through photosynthesis. Peat, mined from bogs, is a kind of sub-fossil biomass. Like hydrocarbon fuels, biomass can be combusted to provide thermal energy for industrial purposes and to heat homes and larger buildings. Biomass can also be combusted in industrial-scale generating stations, usually to generate steam, which may be used to drive a turbine that generates electricity. Biomass can also be used to manufacture methanol, which can be used as a liquid fuel in vehicles and for other purposes.

If the ecosystems from which biomass is harvested are managed to allow post-harvest regeneration of the vegetation, this source of energy can be considered a renewable resource. Peat, however, is always mined faster than the slow rate at which it accumulates in bogs and other wetlands, so it is not a renewable source of biomass energy.

Energy Consumption

The consumption of energy varies greatly among countries, largely depending on differences in their population and degree of development and industrialization (Table 18.5). In general, the per-capita use of primary energy (this refers to fuels that are commercially traded, including renewables used to generate electricity) in less-developed countries is less than about 1 toe per person per year. However, in the less-developed countries there is a relatively larger use of non-commercial or “traditional” fuels for purposes of subsistence and local commerce, such as wood, charcoal, dried animal manure, and food-processing residues such as coconut shells and bagasse (a residue of sugar cane pressing).

Countries that are developing rapidly are intermediate in their per-capita energy consumption, but their rates of energy use are increasing rapidly due to their industrialization. While the use of energy has grown in rapidly developing countries, their reliance on traditional fuels has dropped. This happens because traditional fuels are relatively bulky, smoky, and less convenient to use than electricity or fossil fuels, particularly in the urban environments where people are living in increasingly large numbers. In addition, the supplies of wood, charcoal, and other traditional fuels have become severely depleted in most rapidly developing countries, particularly near urban areas.

Relatively developed countries have a high per-capita consumption of energy. Their energy use is typically more than 3 toe/person and almost entirely involves electricity and fossil fuels. The world’s most energy-intensive economies, on a per-capita basis, are those of Canada and the U.S. (9.38 and 7.13 toe/person, respectively), which have more than 40-50 times the per-capita usage of people living in the least-developed economies of the world. Figure 18.1 depicts consumption of primary energy for selected countries in 2019.

Figure 18.1. Consumption of Primary Energy in Selected Countries in 2019. Consumption is measured in terawatt-hours (TWh). Source: visualization by OurWorldinData.org is licensed under CC BY. Data from BP.

In terms of the total amounts of energy being used, the largest consumers are China , the U.S., and Russia. The use of primary energy in the U.S. increased 81% between 1965 and 2019, while per-capita consumption increased by 10% during the same period, respectively (Figure 18.1). The fact that per-capita energy use increased much less quickly than national consumption suggests that Americans have become more efficient in their use of energy, especially during the more recent period. Smaller automobiles, improved gas economy of vehicles, better insulation of residences and commercial buildings, and the use of more efficient industrial processes have all contributed to this increased efficiency. Nevertheless, although these gains of energy efficiency have been substantial, they have been more than offset by growth in the per-capita ownership of automobiles, consumer electronics, and other energy-demanding products and technologies. Also, important have been large increases in industrial energy use associated with the growth of the natural gas industry and domestic production of petroleum during the past several decades. These latter changes have caused the overall use of energy in U.S. to increase substantially.

The intensive energy usage by Americans reflects the high degree of industrialization of our national economy. Also significant is the relative affluence of average Americans (compared to the global average). Wealth allows people to lead a relatively luxurious lifestyle, with ready access to energy-consuming amenities such as motor vehicles, home appliances, space heating, and air conditioning. The U.S. is also a large country, so there are relatively large expenditures of energy for travelling. In addition, the cold winter climate for some areas means that people use a great deal of energy to keep warm.

Energy Production

As was examined in Chapter 11, a sustainable enterprise cannot be supported primarily by the mining of non-renewable sources of energy or other resources. Therefore, a sustainable economy must be based on the use of renewable sources of energy.

However, most energy production in industrialized countries is based on non-renewable sources (Table 18.6). With such a small reliance on non-renewable sources, it is clear that the major economies of the world are not close to having developed sustainable energy systems. Considering the rapid rate at which reserves of non-renewable energy resources are being depleted, one wonders how long the energy-intensive economies of developed nations can be maintained.

Table 18.6. Energy Consumption in Selected Countries in 2019. Data are in units of TWh. Source: Data from British Petroleum (2019).

Country	Petroleum	Gas	Coal	Nuclear	Hydro	Wind+Solar	Total
U.S.	10,274	8,466	3,150	2,111	671	1,019	26,291
China	7,752	3,073	22,687	863	3,144	1,559	39,361
India	2,844	597	5,172	112	401	272	9,461
Russia	1,825	4,443	1,008	517	481	3	8,279
Australia	595	537	495	0	35	92	1,780

Of the U.S.’s total consumption of primary energy in 2019, 37% came from petroleum, 32% came from natural gas, 11% from coal, and 8% from nuclear energy (Figure 18.2). These non-renewable energy sources account for 80% of the total use of primary energy in the U.S. Another 11% involves the use of other renewable sources of energy, such as wind, solar, hydroelectric, and biomass. There are also, of course, environmental impacts of the harvesting of trees and other kinds of biomass for use as fuel (see Chapter 27).

Electricity produced by public or private utilities accounts for much of the energy used by industry, institutions, and residences in the U.S. Of the nearly 3 million TW-hours of electricity produced in 2019 80% was generated from fossil-fueled sources, and 8% by nuclear technology (U.S. EIA, 2020). Within the renewable sector that comprises 11% of energy consumed, hydro accounted for 22% of the electricity production, wind for 24%, and biomass and other biofuel for 43%.

Conclusions

Non-renewable resources are always diminished as they are used. Although non-renewables can be used with great enthusiasm to achieve economic growth, they cannot be the basis of a sustainable economy. Only renewable resources can play that fundamental role. In this chapter we learned that the non-renewable resources that are vital to the functioning of modern “advanced” economies, such as that of the U.S., are being rapidly depleted. For instance, the life index of the global reserves of copper is only about 39 years, while that of nickel is 30 years, and zinc 19 years. Among fossil fuels, the life index of the global reserves of petroleum is about 51 years, while that of natural gas is 53 years, and coal 114 years. While it is true that continuing exploration will find additional reserves of these and other non-renewable resources, there are limits to those further discoveries. In addition, about 84% of the consumption of primary energy in the U.S. is based on non-renewable sources, as is 63% of the electricity generation. Because the reserves of all non-renewable resources are being depleted rapidly, both in the U.S. and around the world, the longer-term sustainability of the energy-intensive economies of developed countries, and the lifestyles of their citizens, is highly doubtful.

Questions for Review

1. Using information from this chapter, describe the U.S. and global production and use of non-renewable resources.
2. Show how industrialized countries rely mostly on non-renewable resources to sustain their economies. Will this kind of resource use be able to continue for very long? Why or why not?
3. What are the various non-renewable and renewable sources of energy available for use in industrialized countries? What are the future prospects for increasing the use of renewable sources?
4. What are the key sources of energy and materials that are ultimately based on sunlight? Which of these resources would you consider to be renewable, and which not?

Questions for Discussion

1. Outline the ways in which you use energy, both directly and indirectly. For each of your major uses, how could you decrease your energy consumption? How would a decrease in energy consumption affect your lifestyle?
2. What are the apparent barriers to the widespread adoption of renewable sources of materials and energy in advanced economies (such as the U.S.)?
3. What are the roles of non-renewable and renewable resources in a sustainable economy?
4. Make lists of the apparent benefits and risks associated with nuclear power. Focus on resource and environmental issues, such as the depletion of fossil fuels, emissions of greenhouse gases, and the long-term disposal of toxic and hazardous wastes.

Exploring Issues

1. A committee in the House of Representatives is examining the sustainability of the U.S. economy. You are an environmental scientist, and the committee has asked you to advise them on improving the sustainability of the use of materials and energy. What would you tell them about the sustainability of present use? What improvements would you recommend?

References Cited and Further Reading

British Petroleum (BP). 2019. Statistical Review of World Energy 2019. https://www.bp.com/en/global/corporate/energy-economics/statistical-review-of-world-energy.html. Accessed June 14, 2021.

Chiras, D.D., and J.P. Reganold. 2009. Natural Resource Conservation: Management for a Sustainable Future. 10th ed. Prentice Hall, Upper Saddle River, NJ.

Craig, J.R., D.J. Vaughan, B.J. Skinner, and D. Vaughan. 2001. Resources of the Earth: Origin, Use, and Environmental Impact. 3rd ed. Prentice Hall, Upper Saddle River, NJ.

Freedman, B. 1995. Environmental Ecology, 2nd ed. Academic Press, San Diego, CA.

Harris, J.M. and B. Roach. 2014. Environmental and Natural Resource Economics: A Contemporary Approach. 3rd ed. Routledge, New York, NY.

Holechek, J.L., R.A. Cole, J.T. Fisher, and R. Valdez. 2002. Natural Resources: Ecology, Economics, and Policy. 2nd ed. Prentice Hall, East Rutherford, NJ.

National Mining Association (NMA). 2021. Economic Contributions of Mining, 2019. https://nma.org/wp-content/uploads/2018/09/Economic_Contributions_of_Mining_2019.pdf. Accessed June 14, 2021.

NS Energy. 2018. Top five biggest windfarms in the U.S. Oct. 5. https://www.nsenergybusiness.com/news/biggest-wind-farms-us/. Accessed June 21, 2021.

Ripley, E.A., R.E. Redmann, and A.A. Crowder. 1996. Environmental Effects of Mining. St. Lucie Press, Delray Beach, FL.

Tietenberg, T. and L. Lewis. 2011. Environmental and Natural Resource Economics.9th ed. Addison Wesley, Boston, MA.

United States Energy Information Association (U.S. EIA). April 2020. Monthly Energy Review, Table 1.3 and 10.1. https://www.eia.gov/energyexplained/us-energy-facts/. Accessed June 14, 2021.

United States Geological Survey (USGS) 2020. Mineral Commodity Summaries 2020. https://pubs.usgs.gov/periodicals/mcs2020/mcs2020.pdf. Accessed June 14, 2021.