The remains of animals and vegetations that died millions of years ago formed the reserves of fossil fuels in different parts of the world. Fossil fuels are mostly found in three basic types namely natural gas, coal, and petroleum.
The three types of fossil fuels are obtained from different sources. These fuels are mostly produced from different types of zooplankton and phytoplankton. The transformation process of these ancient organisms took millions of years.
As per the biogenic theory, the remains of certain type of algae or plankton form natural gas after several years of transformation. Methane is the most common form of natural gas found from the inner layers of earth. Sometimes natural gas is collected from the surface of the petroleum deposits.
Owing to its low density, natural gas is normally found over the petroleum reserves. Huge reserves of only natural gas are also found in certain parts of the world. This form of fossil fuel is normally used for household purposes. It is also more environment-friendly compared to the other forms of fossil fuels.