How is vegetable oil converted into biodiesel?
A. The chemical reaction to make biodiesel is fairly straight forward. Vegetable oil is a ‘triglyceride’ which means three hydrocarbon chains all attach to the same glycerol molecule. It takes a certain amount of catalyst (in our case, lye) to break off these hydrocarbon chains. In the case of used cooking oils, we must add yet more lye to the reaction to neutralize the “free fatty acids” that have been formed in waste oil. This catalyst is dissolved into methyl alcohol (methanol) with a volume representing 20% of the oil we want to convert. This ‘premix’ is then blended vigorously with the oil to allow complete conversion of the oil. The blending allows the catalyst to break off each hydrocarbon chain, one by one, and bond with a floating methanol molecule to form biodiesel. The stripped glycerol molecules fall to the bottom of the reaction tank where they are removed. Glycerol will represent about 12%-15% of the total mix volume.
