As the energy demand expanding, biodiesel has been acknowledge as an alternative fuel since it is derived from sustainable assets as non-renewable energy sources are depleting day by day. There are some major obstacles in the production of biodiesel including high operating cost and residence time. To minimize the operating cost, waste cooking oil, vegetable oil, animal fat can be used as a feedstock and produce biodiesel through trans-esterification process using catalyst. The second objective of my study is to recover the catalyst. Biodiesel emits a low amount of gases i.e. carbon dioxide, carbon monoxide, unburned hydrocarbons and sulphur.