Fossil fuels are energy sources that form naturally via the long-term decomposition of plants and animals. Fossil fuels like petroleum, coal, and natural gas have satisfied human energy demands since the Industrial Revolution.

The majority of fossil fuel use comes from just a few types of fuels.

1. Coal: Coal is a solid fuel that is composed primarily of carbon. Depending on its carbon composition, coal can be classified as lignite, sub-bituminous, bituminous, or anthracite. The vast majority of coal burned in the United States is bituminous or sub-bituminous. Coal can be extracted via underground mining or strip mining from the surface (sometimes called mountaintop removal).

2. Natural gas: Natural gas is a gaseous fuel. Natural gas extraction can occur during coal mining or oil drilling. Natural gas can also be extracted from oil shales via hydraulic fracturing, or fracking.

3. Oil: Crude oil is a liquid fuel that can be refined to create gasoline, kerosene, propane, jet fuel, paint, and plastics. It can be found in pure liquid form in oil deposits or mixed with viscous sand and rock in tar sands.

Fossil fuels have powered countless sectors of human activity for decades. Uses for fossil fuels include:

• Electricity generation: Coal and natural gas power the majority of power plants around the world. They compete with nuclear power, water power, solar power, and wind power—all of which produce fewer carbon emissions than fossil fuel use—but remain the dominant fuel sources around the world.
• Home heating: Natural gas (a byproduct of coal mining) powers many home heating systems, hot water heaters, and gas stoves. In recent years, concern about in-home burning of nitrogen oxides (found in natural gas) has led some consumer advocacy groups to propose shifting from gas appliances to electric.
• Transportation fuel: Gasoline and diesel, both petroleum products, currently power most consumer vehicles. Aircraft are powered by jet fuel, which is similar in composition to kerosene.
• Plastics: Plastics are created from oil. Plastic manufacturing was initially a byproduct of oil refined for electricity and transit, but now over 300 million tons of plastic are produced every year.

According to the United States Environmental Protection Agency (EPA), the burning of fossil fuels causes community health risks, pollution, and global warming. The environmental impacts of fossil fuels include:

1. Air pollution: The burning of fossil fuels, particularly coal, can release harmful chemicals like sulfur dioxide and carbon monoxide into the air. The health effects of air pollution include severe asthma, which has been observed in regions downwind of coal power plants.

2. Water pollution: The sulfur dioxide released from untreated coal smoke can mix with other elements and produce acid rain, and oil spills poison marine ecosystems. While water pollution is not unique to fossil fuels (even so-called clean energy sources like nuclear can pollute water), unregulated fuel spillage pollutes water and endangers plants, animals, and human health.

3. Global warming: Methane and carbon dioxide emissions stemming from electricity plants, gasoline-burning vehicles, cement manufacturing, and other industrial processes trap heat in Earth’s atmosphere, leading to a surge in global temperatures in recent decades.