In this presentation we report the results of a study on two-step in situ process for obtaining a high FAME yield from microalgae biomass that had high free fatty acids (FFA) content. This was accomplished with a pre-esterification process using heterogeneous catalyst, Amberlyst-15, to reduce FFA content prior to the base-catalyzed transesterification. The two-step in situ process resulted in a much higher FAME yield (up to 94.9 %) than traditional extraction-conversion process (33.1%), H2SO4 catalyzed one-step in situ process (60.9%) and KOH catalyzed one-step in situ process (26.8%). The Amberlyst-15 could be used for 8 cycles without significant loss in activity. Moreover, since Amberlyst-15 could be conveniently retrieved after the pre-esterification, no extra base catalyst was required to neutralize the residue acid before the base-catalyzed transesterification and therefore dramatically reduced the requirement for both acid and base catalysts (more than 96.2% reduction).
The result indicated that Amberlyst-15 was effective to reduce FFA in the in situ pre-esterification. This two-step in situ process has the potential to reduce the microalgal FAME production cost and be more environmental compatible due to the higher FAME yield with reduced catalyst consumption.