Transesterification systems and methods for producing methyl ester are disclosed. In one embodiment, a method for producing methyl ester includes introducing a first charge into a reactor. The first charge contains a triglyceride-containing fat and an alcohol. The method can also include performing a first transesterification reaction in which the triglyceride-containing fat is reacted with the alcohol to produce a first product. The method can further include settling the first product into a methyl ester-containing layer and a glycerol-containing layer, decanting the glycerol-containing layer after settling from the reactor, mixing a second charge with the first product, and performing a second transesterification reaction after mixing the second charge with the first product.