At high methanol to oil molar ratio, the glycerin would largely dissolve in excessive methanol. Subsequently, it reduced the amount of methanol and inhibited the reaction of methanol to the reactants and catalyst, resulted in a lower biodiesel conversion [17] and [22]. Additionally, the polar hydroxyl group in methanol acting as emulsifier making it more difficult to separate the biodiesel product and glycerol [34], eventually reduce the yield of methyl esters.