Coal is a solid fossil fuel, black in color, which is mined to be used as an energy source. During the industrial revolution, coal was the first major fossil fuel used. It powered steam engines on trains and ships, heated homes and offices, and powered factories with their "infernal" smokestacks. Air pollution is a major problem associated with coal combustustion that modern scrubbers on smokestacks have only partially controlled. A significant problem with burning coal is the release of radium with the smoke.
Today, virtually all commercially used coal (more than 90%) is used to generate electricity. About 95% of the coal not used to generate electicity is used as an industrial power source. The residential and commercial use of coal has remained at a more or less constant (miniscule) level since 1980. The use of coal for transportation ended in the 1950s when the last coal fired railroad engines were replaced with diesel engines. Industrial use slowly but surely declined during the post-WWII period, primarily as a result of the cost of complying with environmental regulations. Electric utilities have increased their use of coal tenfold in the past 50 years, and coal now provides 56% of U.S. electrical generation.
Coal's main competitors are nuclear power (21% market share) and hydroelectric power (10% market share), both of which have no significant use other than to generate electricity. In addition natural gas provides about 10% of U.S. electricity generation (which accounts for about 15% of U.S. natural gas consumption), oil about 3%, and other renewables (geothermal, wind, solar, biofuels, etc.) about 0.5%. Those who favor nuclear power, natural gas, and renewable forms of energy generation give as one rationale the environmental impacts of coal-provided power both in terms of air pollution (including but not limited to acid rain) and in terms of environmental damage created in the mining process. Mountain top removal has become one of the most common coal mining techniques in the US, with most of the recent restrictions on it lifted by the Bush administration. In addition, as a fossil fuel, coal releases carbon dioxide into the atmosphere, thus contributing to global warming.
The Bush Administration has pushed "clean coal technology", in part to blunt criticism of coal as an environmental problem, and in part in the belief that there is no realistic alternative for domestic production of electricity. Most of Europe is far less coal dependent in its generation of eletricity, largely as a result of much greater use of nuclear power generators.
Coal is a U.S. export, and reserve coal supplies far exceed reserves of oil and natural gas. Generally it is transported from mines to its final destination by barge and rail. Wyoming strip mines, Colorado underground mines, and West Virginia mines (of both types) are among the main centers of coal production in the United States.
Coal's nature as a solid limits its usefulness today as a transportation fuel. However, the Fischer-Tropsch process, a technology invented by Germans in the 1930s, can convert solid coal into liquid fuels such as gasoline, diesel and jet fuel. This approach is not economical as long as oil costs less than $30/bbl. With skyrocketing petroleum prices in 2004/2005, there has been renewed interest in the Fischer-Tropsch process .