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
Solar power plants in the Mojave Desert preserved, but the solar industry is mainly interested in areas of the western desert, "where the sun burns hotter and there is easier access to transmission lines", said Kenn J. Arnecke of "FPL Energy", a view shared by many industry executives. Concentrating solar plants in the Mojave Desert have brought up issues of water use, because concentrating solar power plants with wet-cooling systems have high water-consumption intensities compared to other types of electric power plants; only fossil-fuel plants with carbon-capture and storage may have higher water intensities. A 2013 study comparing various sources of electricity found that the median water