Final answer:
The two primary methods for synthesizing biodiesel are transesterification, where a triglyceride reacts with an alcohol to produce biodiesel (an ester) and glycerol, and esterification, which reacts a carboxylic acid with alcohol in the presence of an acid catalyst.
Step-by-step explanation:
The two primary methods used for synthesizing biodiesel are transesterification and esterification. In the process of transesterification, a triglyceride reacts with an alcohol (commonly methanol) to produce biodiesel (which is an ester) and glycerol. This is the most common method used in the production of biodiesel. On the other hand, esterification is used when the feedstock oil contains high levels of free fatty acids, which can occur when using waste vegetable oils as the source. It involves the reaction of a carboxylic acid with an alcohol, usually in the presence of an acid catalyst, to form an ester and water.