Biofuels are a renewable energy source, made from organic matter or wastes, that can play a valuable role in reducing carbon dioxide emissions.If the biomass used in the production of biofuel can regrow quickly, the fuel is generally considered to be a form of renewable energy.The two most common types of biofuel are bioethanol and biodiesel.In the transport sector, they are blended with existing fuels such as gasoline and diesel.