Fossil Fuels provide the energy required to produce about 70% of the electric power generated in the US. Fossil fuel includes oil, natural gas and coal.
Fossil fuels or mineral fuels are hydrocarbons found within the top layer of the earth’s crust. They range from very volatile materials with low carbon: hydrogen ratios like methane, to liquid petroleum to nonvolatile materials composed of almost pure carbon, like anthracite coal. It is generally accepted that they formed from the fossilized remains of dead plants and animals by exposure to heat and pressure in the Earth's crust over hundreds of millions of years.
It was estimated that in 2004 86% of human-produced energy came from burning fossil fuels. Fossil fuels are non-renewable resources because they take millions of years to form and reserves are being depleted much faster than new ones are being formed. Concern about fossil fuel supplies is one of the causes of regional and global conflicts. The production and use of fossil fuels raise environmental concerns. A global movement toward the generation of renewable energy is therefore under way to help meet increased energy needs.
The burning of fossil fuels produces around 6.3 billion metric tons (= 6.3 gigatons) of carbon dioxide per year, but it is estimated that natural processes can only absorb about half of that amount so there is a net increase of 3.2 billion tones of atmospheric carbon dioxide per year