Coal is one of the three main fossil fuels. It accounts for a large percentage of energy production from fossil fuels and greenhouse gas emissions.
Coal is formed when organic plant matter is buried and compacted into a solid form over a long period of time. Prior to forming into coal, the organic plant matter takes form as a soft layer known as peat, which may be used as a fuel source. Coal has several forms, such as anthracite, bituminous and brown, with differing energy outputs. It is typically mined from underground deposits and through strip-mining. These mining practices have harmful effects on the environment if used extensively.