Coal (from the Old English term col, which has meant "mineral of fossilized carbon" since the 13th century) is a combustible black or brownish-black sedimentary rock usually occurring in rock strata in layers or veins called coal beds or coal seams. The harder forms, such as anthracite coal, can be regarded as metamorphic rock because of later exposure to elevated temperature and pressure. Coal is composed primarily of carbon along with variable quantities of other elements, chiefly hydrogen, sulfur, oxygen, and nitrogen.
Throughout history, coal has been a useful resource. It is primarily burned for the production of electricity and/or heat, and is also used for industrial purposes, such as refining metals. A fossil fuel, coal forms when dead plant matter is converted into peat, which in turn is converted into lignite, then sub-bituminous coal, then bituminous coal, and lastly anthracite. This involves biological and geological processes that take place over a long period.
Coal is the largest source of energy for the generation of electricity worldwide, as well as one of the largest worldwide anthropogenic sources of carbon dioxide releases. In 1999 world gross carbon dioxide emissions from coal usage were 8,666 million tonnes of carbon dioxide.
Coal-fired electric power generation emits around 2,000 pounds of carbon dioxide for every megawatt-hour generated, which is almost double the carbon dioxide released by a natural gas-fired electric plant per megawatt-hour generated. Because of this higher carbon efficiency of natural gas generation, as the fuel mix in the United States has changed to reduce coal and increase natural gas generation, carbon dioxide emissions have unexpectedly fallen. Those measured in the first quarter of 2012 were the lowest of any recorded for the first quarter of any year since 1992.
Coal is extracted from the ground by coal mining, either underground by shaft mining, or at ground level by open pit mining extraction.
The top hard and brown coal producers in 2010 (and 2009) were (in millions of tons): China 3,162 (2,971); United States 997 (985); India 571 (571); Australia 420 (399); Indonesia 336 (301); Russia 324 (297); South Africa 255 (247); Poland 134 (135); Kazakhstan 111 (101); and Colombia 74 (73).
Read more about Coal: Formation, Types, Early Uses As Fuel, Cultural Usage, Coal As A Traded Commodity, Environmental Effects, Economic Aspects, Energy Density and Carbon Impact, Underground Fires, Production Trends
Famous quotes containing the word coal:
“The rooms very hot, with all this crowd, the Professor said to Sylvie. I wonder why they dont put some lumps of ice in the grate? You fill it with lumps of coal in the winter, you know, and you sit round it and enjoy the warmth. How jolly it would be to fill it now with lumps of ice, and sit round it and enjoy the coolth!”
—Lewis Carroll [Charles Lutwidge Dodgson] (18321898)
“Coal lay in ledges under the ground since the Flood, until a laborer with pick and windlass brings it to the surface. We may will call it black diamonds. Every basket is power and civilization. For coal is a portable climate.”
—Ralph Waldo Emerson (18031882)
“And in their blazing solitude
The stars sang in their sockets through the night:
Blow bright, blow bright
The coal of this unquickened world.”
—Philip Larkin (19221986)