Transesterification of waste fryer grease (WFG) containing 5–6 wt.% free fatty acid (FFA) was carried out with methanol, ethanol, and
mixtures of methanol/ethanol maintaining the oil to alcohol molar ratio of 1:6, and initially with KOH as a catalyst. Mixtures of methanol and
ethanol were used for transesterification in order to use the better solvent property of ethanol and rapid equilibrium using methanol. Formation of
soap by reaction of FFA present in WFG with KOH instigated difficulty in the separation of glycerol from biodiesel ester.