Biodiesel is obtained from the transesterification of vegetable oils or animal fats with a short-chain alcohol, with or without the use of catalyst. After the reaction glycerol (the main byproduct) is separated by settling or centrifuging and a crude biodiesel phase is thus obtained. Many contaminants can still be present in the crude biodiesel depending on the technology of transesterification used. Impurities such as residual methanol and traces of glycerol, soaps, catalyst, phospholipids, water and unreacted glycerides can be found, that can produce harmful