Saponification not only consumes the alkali catalyst, but also the resulting soaps can cause the formation of emulsions.
Emulsion formation creates difficulties in downstream recovery and purification of the biodiesel. Thus, dehydrated
vegetable oil with less than 0.5 wt.% free fatty acids, an anhydrous alkali catalyst and anhydrous alcohol
are necessary for commercially viable alkali-catalyzed systems (Freedman et al., 1984; Jeromin et al.,
1987)