Renewable fuel is a type of energy source that can be replenished naturally and does not deplete the environment. Two examples of renewable fuels are ETHANOL and biogas. ETHANOL is an alcohol-based fuel made from plant materials such as corn, sugar cane, and wheat. Biogas is a gas produced by the breakdown of organic matter in the absence of oxygen, usually from animal or plant waste. Both ETHANOL and biogas are used to power vehicles and generate electricity.