Fuels formed from animal or plant remains that become fossilised or trapped in geological strata, chiefly coal, oil and natural gas.
Any naturally occurring solid, liquid or gaseous fuel of a fossilized organic nature. Includes coal, crude oil and natural gas.
Hydrocarbons derived from dead, fossilized plant and animal matter. Due to the fact that they take millions of years to form, they are considered non-renewable resources.