Depending upon the oil acidity, an extra amount of catalyst has to be added in order to neutralize the free fatty acids. For the oils with acidities 0.41%, 1.13% and 1.85%, the amount of catalyst needed to neutralize the free fatty acids were 1.2, 3.3 and 5.4 mol%, respectively. These amounts represent 13.3%, 29.6%, and 40.8% of the total amount of catalyst loaded in the reactor for the oils with acidities 0.41%, 1.13%, and 1.85%, respectively. This extra amount reacts with the free fatty acids, and consequently is consumed very fast in the reaction media, forming soaps. Table 1 shows the concentrations needed for each catalyst and oil, in order to neutralize the oil and catalyze the reaction.