Acid Esterification.
Esterification increases the yield of biodiesel. When oil feedstocks contain an excess of free fatty acids they have to go through the process of esterification. The key to effectively preparing for the esterification process is to make sure the feedstocks have been sufficiently filtered by removing all contaminants and water. Upon filtration the feedstocks are fed to the acid esterification process. The catalyst, sulfuric acid, is dissolved in methanol and then mixed with the pretreated oil. Once the mixture is heated and stirred, the free fatty acids are converted to biodiesel. The final step of esterification is to dewater and feed the product to the transesterification process.