Coal Resource Use
Coal Resource Use
Forty percent of the world’s electricity, including about 50% of the United States’s electricity, is produced by burning coal, a black or brown rock consisting mostly of carbon. Burning coal releases pollutants, including sulfur dioxide and mercury, which can cause disease, acid rain, and global warming. However, coal is one of the cheapest sources of energy and its use is increasing around the world. The World Coal Institute, an industry group, estimated in 2007 that at current usage levels, proven global coal reserves could last 147 years, although global usage is rising rapidly and estimates of proven reserves have been pronounced unreliable by the U.S. government.
Historical Background and Scientific Foundations
Small quantities of coal also appear on Earth’s surface as outcroppings, and this outcrop coal has been used occasionally as a fuel before the industrial period. The large-scale mining of underground coal did not begin until the thirteenth century. At that time, coal became an important fuel in Europe because much of the forests had been cut down, creating the world’s first known energy crisis.From the Middle Ages to the early 1700s, coal was burned in furnaces or fireplaces and to heat buildings. Coal was first used to power machines in 1712, when Englishman Thomas Newcomen (1663–1729) demonstrated the world’s first coal-powered steam engine. The Newcomen engine could pump water out of mines much more cheaply than had hitherto been possible, and so made coal, its own fuel, significantly cheaper. Although it was crude by modern standards, soon more efficient coal engines were powering factories, ships, and trains. The first century and half of the industrial age was fueled by coal.
Coal is a flammable black rock consisting mostly of carbon. It is formed naturally from the compressed, chemically transformed remnants of ancient plants. Most coal derives from plants that grew in vast swamps about 286-300 million years ago, a geological period named the Carboniferous because of its association with coal. In the western United States, important coal deposits also formed during the later Cretaceous and Tertiary periods. Coal is not being formed at a significant rate today, so it is not classified as a renewable resource.
Because the plant matter in coal was laid down by swamps, it tends to occur in extensive horizontal layers called seams or beds. After accumulating in thick beds, the dead plant materials that would eventually become coal were typically covered by sediments (rock particles) that hardened into layers of sedimentary rock. To obtain coal today, miners must typically either tunnel through this rock, a practice known as underground mining, or strip it entirely away—along with the overlying land-scape—to expose the underlying coal seam. The latter practice, known as strip mining, includes the practice of mountaintop removal, in which the upper portions of entire mountains are removed and dumped into adjacent valleys.
There are several grades or qualities of coal, distinguished by hardness and composition. Softer, lower-carbon coals burn less well and pollute more, but are in greater supply. Lignite, the lowest grade of coal, is 40% to 70% carbon by weight; bituminous coal is from 70% to 90% carbon; and anthracite, the hardest, highest-carbon coal, is 90% or more carbon. Although estimates of world coal resources are based partly on guesswork, most experts agree that many billions of tons of coal remain in underground deposits.
Coal Usage and Resources
Oil (petroleum) became essential to transportation in the late nineteenth and early twentieth centuries, and
WORDS TO KNOW
BASELINE POWER: The amount of steady, non-intermittent electric power that is constantly being produced by a power source.
PRIMARY ENERGY SUPPLY: The total amount of available energy embodied in natural resources (such as coal) that has not been subjected to any conversion or transformation processes.
RENEWABLE RESOURCE: Any resource that is renewed or replaced fairly rapidly (on human historical time-scales) by natural or managed processes.
natural gas was first exploited on a mass scale in the 1950s and 1960s. Despite industrial society’s dependence on these additional fuels, coal has remained important. In 2006, the world was using more coal than ever, about 6.28 billion tons per year; that was 7.6% more than in 2005, and about twice as much as in 1990. As of 2005, 25% of world primary energy (heat energy from fuel before it is transformed into electricity or other forms, as well as electricity produced directly, as by hydroelectric dams, solar cells, or windmills) was obtained from coal, 35% from oil, 21% from natural gas, 12% from renewables (including hydro power), and 6% from nuclear power. About 90% of coal was used for electricity generation, with most of the rest being used to provide process heat in steel and concrete manufacture.
Coal is particularly important in making electricity. Heat from burning coal is used to make pressurized steam, which turns turbines that turn generators that produce electricity. In 2007, 40% of world electricity electric dams, 15% from nuclear power, 7% from oil, and 20% from miscellaneous sources, including non-hydro renewables. In specific countries, the mix varied. In Poland, for example, 93% of electricity was coal-generated in 2006, while in Germany only 47% was. In the United States, the world’s largest energy consumer, 56% of electricity was coal-generated. In 2007, coal cost about one sixth as much per unit of energy released as did oil or natural gas (namely, $1-2 per million British thermal units for coal versus $6-12 for oil or natural gas). These standard figures do not count the money costs of the so-called externalities of coal burning, such as lung disease, destruction from strip mining, and climate change. Although by 2007, wind power had become the cheapest form of new electric generation capacity, it could not be used for baseline generation, the making of electricity to meet steady, around-the-clock demand (the wind does not blow all the time).
Estimates of how much coal remains in the ground worldwide vary widely. Energy experts distinguish between coal reserves and coal resources. Reserves are quantities of unearthed coal that are proven to exist and to be recoverable. Resources are coal deposits whose existence is assumed based on past patterns of discovery, but which have not been actually found. Estimates of world coal resources (undiscovered coal) are unreliable, and shrank from 1980 to 2005 by about 50%, to a little less than one trillion tons. World coal reserves are considerably smaller, about half a trillion tons. Although recoverable coal reserves exist in about 70 countries, 85% of proven coal reserves are found in just six countries, namely (in order of decreasing quantity) the United States, Russia, India, China, Australia, and South Africa. The United States alone held about 30% of world reserves, some 120 billion tons. However, figures even for supposedly proven reserves can be inaccurate. In 2004, Germany decreased its official estimate of its hard coal reserves by 99%, from 23 billion tons to 183 million tons. The change, according to the World Energy Council, was due to the fact that earlier estimates of proven reserves were, in fact, mostly speculative.
In 2005, China was the world’s largest coal producer and consumer, producing about 1.1 billion tons a year (with reserves of 59 billion tons, giving an annual depletion rate of 1.9% per year). The United States was second, producing 576 billion tons a year; Australia was third, producing 202 billion tons a year; and India was fourth, producing 200 billions tons a year. Although the United States was producing more coal by weight in 2005 than ever before, more of the coal being produced was low-carbon sub-bituminous coal, so in terms of energy production, the U.S. coal industry had actually peaked in 2000. Although global coal production was rising, a 2007 study by the Energy Watch Group predicted that world coal production was likely to peak around 2030 at about 30% above 2007 levels, then decline slowly thereafter to 1990 levels by about 2100. In 2007, China was opening two large (500 megawatt)coal-fired plants per week, adding as much coal-fired electric generating capacity every year as the entire power grid of the United Kingdom.
Impacts and Issues
Coal and the Environment
Coal’s damage to the environment begins during mining. Strip mining, which supplies about 70% of U.S. coal, annihilates existing landscapes above the area mined for coal and destroys additional area that is buried under the removed overburden, as the material covering the coal seam is termed. In both shaft and strip mines, sulfur from coal dissolves in water, entering streams and aquifers as sulfuric acid. Toxic heavy metals dissolve in the acidic water and accumulate in aquatic food chains. Solid mine wastes are bulky, toxic, and often flammable. Coal mines release methane, another greenhouse gas.
When coal is burned, it releases scores of pollutants, including mercury, sulfur dioxide (which returns to Earth as acid rain), nitrogen oxides, soot particles, mercury, cadmium, uranium, and lead. According to a 2007 World Bank report, air pollution from coal causes on the order of 400,000 deaths annually in China alone. A 2004 study commissioned by environmental groups (but carried out by a firm often employed by the U.S. Environmental Protection Agency for similar work) found that burning coal contributes to about 24,000 deaths per year in the United States, including over 8,000 from lung cancer. The accuracy of the latter study was disputed by representatives of the coal industry.
Coal and Climate Change
Before people started burning large amounts of coal—1750 is the date usually named as a reference—the concentration of CO2 in the atmosphere was about 280 parts per million (that is, about 280 out of every 1 million molecules in any given volume of air were CO2 molecules). By 2008, it was 385 parts per million, a 37.5% increase over the pre-industrial value. Most of this CO2 had come from coal, with the second-largest share coming from oil. By 2008 humans had released about 170 billion tons of carbon into the atmosphere from burning coal, about half of which had been absorbed by the oceans and elsewhere and half of which remained in the atmosphere. Carbon dioxide, methane, and several other gases—known collectively as greenhouse gases—are the main cause of the global climate changes that are now occurring.
As of 2004, about 80% of all greenhouse-gas emissions consisted of CO2 released from burning fossil fuels. This CO2 was responsible for about 63% of the extra energy retention (radiative imbalance) causing global warming. The other 5% of greenhouse-gas emissions from energy production consisted of methane from coal mines and hydroelectric dams and nitrogen-oxygen (NOx) compounds from burning various fossil fuels. Because coal is more carbon-intensive than oil or natural gas, releasing almost all its energy from combustion of carbon rather than of hydrogen, it produces a larger share of CO2 emissions than it does of primary energy. Thus, coal produced 40% of global CO2 emissions but only 25% of global primary energy (raw heat energy, most of which is not captured for useful work). Coal is about twice as carbon-intensive per unit of useful energy produced as is natural gas.
In the early 2000s, global CO2 emissions were increasingly rapidly. From 2003 to 2004 alone, annual emissions increased by over 1.2 billion tons of CO2, with 86% of this rise caused by increasing energy demand in developing countries. Increased coal usage accounted for 60% of the 2003–2004 increase in global CO2 emissions. In the United States, coal usage is constrained not by a lack of raw coal in the ground, but by competition from cheaper rivals such as wind power, cleaner rivals such as natural gas, and resistance to coal on account of its environmental destructiveness.
Clean Coal Technologies
Although climate-friendly renewable energy resources were expanding rapidly in the early 2000s (over 30% per year for wind power), and some experts were urging a rapid expansion of nuclear power, coal was expected to supply most expansion in primary energy for some years to come. At the same time, concern was mounting about the impact of coal on climate. In April 2007, a U.S. Supreme Court decision ruled that greenhouse gases, including CO2, are pollutants under the terms of the federal Clean Air Act.
The only way to use steady or increasing amounts of coal while reducing CO2 emissions is to employ carbon capture and storage (CCS) technologies, also known as carbon sequestration or clean-coal technologies. Most
IN CONTEXT: SOOT AS AMAJOR CONTRIBUTOR TOCLIMATE CHANGE
In 2008 researchers studying soot released by cooking fires in South Asia and coal-burning in East Asia concluded that soot is a more important contributor to global warming than had been hitherto known, edging out methane as the second-largest greenhouse pollutant after carbon dioxide. Melting of glaciers in the Himalaya mountains may be as much due to soot as to carbon dioxide. Dimming of the skies by soot reduces evaporation and regional temperature differences over the Indian Ocean, causing less rain to fall during the monsoon season and so contributing to drought in Southeast Asia. The new estimate of the radiative forcing (energy imbalance between Earth and sunlight) caused by soot was about double that cited by the Intergovernmental Panel on Climate Change (IPCC) in its influential 2007 summary of the state of climate science. Replacing dung and wood as cooking fuels in South Asia with biogas, natural gas, and solar cookers could significantly reduce the problem.
CCS schemes involve pumping CO2 from power plants into ocean waters or deep underground reservoirs rather than allowing it to escape into the air. Concerns about CCS involved its cost, whether marine sequestration would enhance acidification of the oceans, and whether gas pumped into underground reservoirs would stay put. Also, CCS cannot reduce the environmental harm done by mining coal.
Primary Source Connection
The following news article recognizes that under the influence of “greener” philosophies, society frowns upon the use of coal in the face of Earth-healthy renewable energy. States are turning down coal-powered plants that are associated with dirty conditions, excessive CO2 (indicated in the article as CO2) emissions, and bad health. National politics play a significant role in the rejection of coal-based business as issues of climate change make a more striking presence in governing.
KING COAL’S CROWN IS LOSING SOME LUSTER
Because of its link to carbon dioxide, the main greenhouse gas causing global warming, coal sometimes seems like the Rodney Dangerfield of energy sources: It gets no respect.
In recent days, there’s been a new report on the dirtiest power plants in the United States, Senate majority leader Harry Reid (D) has said he opposes new coal-fired power plants in his home state of Nevada, and an increasing number of proposed plants reportedly are either being canceled or delayed. A new Massachusetts Institute of Technology (MIT) report, meanwhile, finds that “a significant reduction of carbon emissions is possible” in burning coal for power, but “only when a significant price is placed on CO2 emissions.”
The report on dirty power plants comes from the Environmental Integrity Project, a research and advocacy group in Washington founded by the former head of the Environmental Protection Agency’s regulatory enforcement office. Among the report’s findings: “… the carbon dioxide (CO2) pollution linked to global warming from large, old, and inefficient electricity-generating facilities continues unchecked and could rise 34 percent by 2030….”
In its coverage of the report, the Environment News Service notes that 50 plants identified as the worst polluters—out of the 378 largest US power plants in the study—are scattered around the country. “The 12 states with the heaviest concentrations of the dirtiest power plants, in terms of total tons of carbon dioxide emitted, are—Texas, which has five, including two of the top 10 dirtiest plants; Pennsylvania with four; Indiana with four, including two of the top 10 dirtiest plants; Alabama with three; Georgia with three, including two of the top three dirtiest plants; North Carolina, Ohio and West Virginia have three apiece; while Wyoming, Florida, Kentucky and New Mexico each have two.”
Such news seems to be part of a pattern around the country, indicated in the headline over an editorial in the Independent Record newspaper in Helena, Mont.: “Coal plant prospects poor.” “Last week was a tough one for proposed coal plants in Montana—the Bull Mountain plant near Roundup hit a permit snag and an environmental group filed a federal lawsuit to stop the Highway Generating Station near Great Falls—but coal-plant woes aren’t limited to Montana. “… “Across the country, prospects for new coal-fired generators just keep getting blacker.”
According to The Wall Street Journal, “plans for a new generation of coal-fired power plants are falling by the wayside as states conclude that conventional coal plants are too dirty to build and the cost of cleaner plants is too high.”… “As recently as May, US power companies had announced intentions to build as many as 150 new generating plants fueled by coal, which currently supplies about half the nation’s electricity. But as plans for this fleet of new coal-powered plants move forward, an increasing number are being canceled or development slowed.”
An early sign of the changing momentum, reports the Journal, came earlier this year with the $32 billion private-equity buyout of the TXU Corp. As part of that deal, the buyers eliminated 8 of 11 coal plants TXU had proposed in Texas. The Journal report cites a change of plan in other states as well. “Recent reversals in Florida, North Carolina, Oregon and other states have shown coals future prospects are dimming. Nearly two dozen coal projects have been canceled since early 2006….”
National political concern over climate change is at play here. Other plants are in trouble in Nevada, where Senator Reid has announced he will “do everything I can” to stop three proposed coal-fired power plants, reports The Salt Lake Tribune. The newspaper cites a letter from Reid to the energy companies planning to build the plants, in which the senator wrote: “Because I believe that developing renewable energy in Nevada is far preferable to coal for the sake of our economy, public health and the environment, I will use every means at my disposal to prevent the construction of new coal-fired power plants in Nevada that do not capture and permanently store greenhouse-gas emissions.”
Coal will continue to play a large role in a world where greenhouse gases are constrained, MIT researchers report. The capturing and storing of carbon that Reid refers to “… is the critical enabling technology to help reduce CO2 emissions significantly while also allowing coal to meet the world’s pressing energy needs,” they state in their March report, “The Future of Coal.”
The use of that technology will make the cost of electricity significantly higher than it would otherwise be, the MIT experts found. But they also identify a way to blunt the cost impact. “Disciplined technology development and innovative advances can… narrow the cost gap and deserve support.”
As with so much that has to do with energy policy and climate change, political will may be more important here than engineering skills.
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Associated Press. “Coal Use Grows Despite Warming Worries.” New York Times (October 28, 2007).
Berstein, Lenny, et al. “Carbon Dioxide Capture and Storage: A Status Report” Climate Policy 6 (2006): 241-246.
Sanderson, Katharine. “King Coal Constrained.” Nature 449 (2007): 14-15.
Energy Information Administration. “U.S. Coal Supply and Demand: 2007 Review.” http://www.eia.doe.gov/cneaf/coal/page/special/feature07.pdf (accessed April 30, 2008).