Fossil Fuels

Oil, natural gas, and coal formed over millions of years, primarily from the remains of dead plants. The remains became buried under sediments and rock. Organic matter from the plant material was incorporated into sediments and buried at increasing depth. Heat and pressure transformed the organic matter into coal, oil, and natural gas that we extract and use today.

Because it takes millions of years to make fossil fuels, we call them non-renewable fuels. Other fuels are called renewable because they are continually renewed at a relatively rapid rate, and therefore do not run out. One example of a renewable fuel is ethanol, a transportation alcohol fuel made from crops such as sugar cane and corn.

At the rate we are using them, the earth's reserves of oil and gas may be used up in 100 years, and coal in about 230 years. Reserves are the identified deposits that can be recovered economically. In addition, there are undiscovered resources in the ground and under the sea. But no one really knows the extent of these undiscovered resources.