Fossil fuel embedded energy is still photosynthetic in origin. Terrestrial plants, on the other hand, tended to form coal and methane. Many of the coal fields date to the Carboniferous period of Earth's history. Terrestrial plants also form type III kerogen, a source of natural gas. There is a wide range of organic, or hydrocarbon, compounds in any given fuel mixture. The specific mixture of hydrocarbons gives a fuel its characteristic properties, such as boiling point, melting point, density, viscosity, etc. Some fuels like natural gas, for instance, contain only very low boiling, gaseous components. Others such as gasoline or diesel contain
Economics of nuclear power plants nuclear disaster in 2011, costs are likely to go up for currently operating and new nuclear power plants, due to increased requirements for on-site spent fuel management and elevated design basis threats. After Fukushima, the International Energy Agency halved its estimate of additional nuclear generating capacity built by 2035. Many license applications filed with the U.S. Nuclear Regulatory Commission for proposed new reactors have been suspended or cancelled. As of October 2011, plans for about 30 new reactors in the United States have been reduced to 14. There are currently five new nuclear plants under construction in the United States