Fuel were present at the sites. As a fuel, wood has remained in use up until the present day, although it has been superseded for many purposes by other sources. Wood has an energy density of 10–20 MJ/kg. Recently biofuels have been developed for use in automotive transport (for example Bioethanol and Biodiesel), but there is widespread public debate about how carbon efficient these fuels are. Fossil fuels are hydrocarbons, primarily coal and petroleum (liquid petroleum or natural gas), formed from the fossilized remains of ancient plants and animals by exposure to high heat and pressure in the absence of oxygen
Economics of nuclear power plants dilution of highly enriched weapons-grade uranium from the decommissioning of nuclear weapons and related military stockpiles with depleted uranium, natural uranium, or partially-enriched uranium sources to produce low-enriched uranium for use in commercial power reactors. Similar efforts have been utilizing weapons-grade plutonium to produce mixed oxide (MOX) fuel, which is also produced from reprocessing used fuel. Other components of used fuel are currently less commonly utilized, but have a substantial capacity for reuse, especially so in next-generation fast neutron reactors. Over 35 European reactors are licensed to use MOX fuel, as well as Russian and American nuclear plants. Reprocessing of