Fossil Fuel

Carbon-based energy sources extracted from geological deposits formed over millions of years from organic matter, burned or processed to release their stored chemical energy, including coal, crude oil, natural gas and their unconventional forms coalbed methane, oil sands, oil shale, peat and shale gas. Belongs here: any source whose energy content derives from ancient buried organic material and that yields net carbon emissions on use. Does not belong here: pre-commercial or unconventional resources still awaiting fuel-cycle maturity, grouped under Prospective, even where they share a fossil origin, such as methane hydrates; traditional solid biomass burned directly for heat, grouped under Traditional Biomass, which is combusted organic matter but not a geological fossil deposit.