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Coal is a type of fossil fuel, formed when dead plant matter decays into peat which is converted into coal by the heat and pressure of deep burial over millions of years. [2] Vast deposits of coal originate in former wetlands called coal forests that covered much of the Earth's tropical land areas during the late Carboniferous ( Pennsylvanian ...
Despite these heat-driven transformations, the energy released in combustion is still photosynthetic in origin. [24] Terrestrial plants tended to form coal and methane. Many of the coal fields date to the Carboniferous period of Earth's history. Terrestrial plants also form type III kerogen, a source of natural gas.
In 2021, coal supplied 9.5 quadrillion British thermal units (2,800 TWh) of primary energy to electric power plants, [4] which made up 90% of coal's contribution to U.S. energy supply. [5] Utilities buy more than 90% of the coal consumed in the United States. [6] There were over 200 coal powered units across the United States in 2024.
By the late 20th century, coal was, for the most part, replaced in domestic as well as industrial and transportation usage by oil, natural gas or electricity produced from oil, gas, nuclear power or renewable energy sources. By 2010, coal produced over a fourth of the world's energy. [2] Since 1890, coal mining has also been a political and ...
The energy value of coal, or fuel content, is the amount of potential energy coal contains that can be converted into heat. [1] This value can be calculated and compared with different grades of coal and other combustible materials, which produce different amounts of heat according to their grade.
Bituminous coal is a particular rank of coal, as determined by the amount and type of carbon present in the coal and the amount of energy it can produce when burned. [2] It is higher in rank than sub-bituminous coal but lower in rank than anthracite. [3] Bituminous coal is the most abundant rank of coal. [3] [2]
A coal mine in Wyoming, United States. Coal, produced over millions of years, is a finite and non-renewable resource on a human time scale.. A non-renewable resource (also called a finite resource) is a natural resource that cannot be readily replaced by natural means at a pace quick enough to keep up with consumption. [1]
In this respect, gasification has a significant advantage over conventional combustion of mined coal, in which CO 2 resulting from combustion is considerably diluted by nitrogen and residual oxygen in the near-ambient pressure combustion exhaust, making it relatively difficult, energy-intensive, and expensive to capture the CO 2 (this is known ...