Most of the energy used in the world comes from the combustion of organic compounds, such compounds are fossil fuels. They are finite resources and when we have used up Earth's reserves no more will be formed. We use fuels as if there is unlimited reserves but they are not. Although they have many advantages but the disadvantages are taking a toll on our ecosystem. These fuels contain sulphur which when reacts with oxygen and water they form acidic rain. However the biggest drawback is the formation of carbon dioxide or greenhouse gas.