Fossil fuels (coal and petroleum) that are being increasingly used are a non-renewable source of energy. They take millions of years to get replenished as they are formed from degradation of bio-mass. Fossil fuels being majorly responsible for increasing air pollution must be replaced by alternate source of energy. Burning of fossil fuels release carbon dioxide and certain poisonous gases such as carbon monoxide, sulphur dioxide and nitrogen dioxide in our environment. Moreover, fossil fuels serve as a reservoir of carbon and combustion of carbon produces CO₂. High concentration of CO₂ leads to increased global warming.