Fossil fuels are fuels produced by natural processes by anaerobic decomposition of buried dead organisms. Coal, oil, and natural gas constitute the three major states of fossil fuels. All these have been formed from organic remain of prehistoric plants and animals, under high pressure, high temperature conditions. All three forms are excellent energy sources, upon which modern day civilization is based. Coal is used as a domestic as well as industrial fuel in all three forms: anthracite, bituminous, and lignite. Fractional liquid petroleum is used as automobile and industrial fuel, in all of its variations, viz. gasoline, kerosene, diesel, light oil, heavy oil, green oil, etc. Natural gas is mainly methane, and is a component of domestic and industrial gas supply lines, for use as an easily accessible fuel.
