Srivastava and Prasad [16] established that the maximum level of activity of alkaline catalysts occurs in the range of 0.5–1 wt% based on oil, with oil conversions from 94 to 99%. On the other hand, Ma et al. [17] reported that the maximum catalyst activity in tallow methanolysis was obtained with 0.3 wt%. Darkono and Cheryan [14] reported that for reactions at 60 C and 0.5 wt% of KOH as catalyst, the concentration of methyl esters showed an initial phase controlled by the diffusion. In this study that behavior was not observed even for reactions at 50 C and 0.2 wt% of NaOH, probably because the mixture regime was turbulent enough to reduce the problems of mass