Fossil fuels are hydrocarbon-based energy sources that have been formed over hundreds of millions of years from the remains of plants and animals. They are considered non-renewable sources of energy, as the rate of formation of such deposits is much slower than the rate of consumption. Fossil fuels are the most widely used energy sources today and include coal, oil, and natural gas. They are used to generate electricity and power motor vehicles, airplanes, and ships, but their combustion also releases carbon dioxide and other greenhouse gases into the atmosphere.

See also: fossil carbon, fossil hydrocarbons, fossil energy, carbon pulse