- Petroleum, natural gas, and coal are the main sources of energy for modern use. All of these fuels are classified asfossil fuels . The reason they are called fossil fuels is because they are all made from decayed plants and animals that have been preserved in the earth 's crust by pressure, bacterial processes and heat. It takes millions of years for these organisms to chemically change into fossil fuels. we need to conserve them because these are non-renewable resources means these can not be re-produced.
It is a fossil fuel which is obtained, when large quantities of dead organisms, usually zooplankton and algae, are buried underneath sedimentary rock and undergo intense heat and pressure.
It is also called as 'Black Gold' because of it is very expensive, useful and valuable and its crude form is black in colour.
the advantages of using c ompressed natural gas (CNG) and liquified petroleum gas (LPG) as fuels are:
(i) They can be burnt directly.
(ii) They can be transported easily through pipe lines.
(iii) They are clean fuels and do not give smoke when burnt.a
(iv) They give a lot of heat energy when burnt.