Energy is required for ground, water, and air transportation as well as power for industrial and farming machinery. Demand for energy is met mostly by fossil fuels. However, fossil fuel has many disadvantages such as emissions of pollutants are directly harmful to health. Also, it produces greenhouse gases which contribute to global warming. Fossil fuels has limited supply but the demand for energy worldwide is increasing day by day. Due to all these reasons the development of renewable sources of energy is encouraged. Bio fuel is one kind of renewable energy source. Bio fuels are fuels in the liquid or gaseous form and are produced from bio mass. Bio mass is an abbreviation of the term biological mass and describes the quantity of living thing (plants, animals and their products). Bio fuels are produced from these biological sources directly or indirectly. Ethanol and biodiesel are the two most common type of biofuels.