Basic catalysts present the disadvantage of soaps formation,
either by free fatty acid neutralization (Eq. (2)) or by acyl-glycerides
saponification (Eq. (3)), which occurs in the presence of
water. Soap formation is undesirable since it consumes catalyst,
hinders phase separation and biodiesel purification, and diminishes
the process yield [3]. Low yields are mainly due to the occurrence
of these two reactions.