Coal is a combustible black or brownish-black sedimentary rock composed mostly of carbon and hydrocarbons. It is the most abundant fossil fuel produced in the United States. Over 90 percent of the coal used in the United States is used to generate electricity. It's also used as a basic energy source in many industries, including, steel, cement and paper.
Nuclear power is a type of nuclear technology involving the controlled use of nuclear reactions, usually nuclear fission, to release energy for work including propulsion, heat, and the generation of electricity. Nuclear energy is produced by a controlled nuclear chain reaction and creates heat—which is used to boil water, produce steam, and drive a steam turbine. The turbine can be used for mechanical work and also to generate electricity.
Crude oil and natural gas are naturally occurring substances present in rock amidst the earth's crust. The origin of oil and gas is organic material - the remains of plants and animals - compressed in sedimentary rock such as sandstone, limestone and shale. Sedimentary rock is a product of sediment deposits in ancient oceans and other bodies of water. As layers of sediment were deposited on the ocean floor, decaying remains of plants and animals were integrated into the forming rock. This organic material eventually transformed into oil and gas after being exposed to a specific temperature and pressure range deep within the earth's crust.
Oil & Tar Sands are a colloquialism for what are technically described as bituminous sands, and commonly known as oil sands or (in Venezuela) extra heavy oil. The sands are naturally occurring mixtures of sand or clay, water and an extremely dense and viscous form of petroleum called bitumen. They are found in large amounts in many countries throughout the world, but are found in extremely large quantities in Canada and Venezuela.
The United States has the largest known deposits of oil shale in the world, according to the Bureau of Land Management and holds an estimated 2,500 gigabarrels of potentially recoverable oil, enough to meet U.S. demand for oil at current rates for 110 years. However, oil shale does not actually contain oil, but a waxy oil precursor known as kerogen. For this reason and because there is not yet any significant commercial production of oil from oil shale in the United States as of 2008, its oil shale reserves do not meet the petroleum industry definition of proven oil reserves.