Coal, oil and natural gas all produce heat energy when burned. These fuels were formed by the remains of organisms that existed millions of years ago. Heat from these fuels is used to convert water into steam, which is then used to power turbines that generate electricity.
Fossil fuels are created over a period of millions of years when the remains of plants and animals are subjected to the intense heat and pressure that is found within the earth's crust. Fossil fuels have been a key energy source for widespread industrial development and are commonly used to power many vehicles, in addition to serving as a fuel source for the generation of electrical power. Fossil fuels are also used to create asphalt, plastics and other materials.
Despite their widespread usage, fossil fuels have several disadvantages that can limit their desirability and usefulness. Coal, oil and natural gas are considered nonrenewable resources because the creation of new fossil fuels requires millions of years. Because they are composed of hydrocarbons, fossil fuels release carbon dioxide gas, which contributes to global warming, into the atmosphere when they are burned. Oil and coal also produce sulfur dioxide, a gas that contributes to respiratory problems and acid rain.