5-17: High efficiency biodiesel production from microalgae via a two-step in situ process

Monday, April 29, 2013
Exhibit Hall
Tao Dong, Jun Wang, Chao Miao, Yubin Zheng and Shulin Chen, Biological Systems Engineering, Washington State University, Pullman, WA
The productivity of fatty acid methyl ester (FAME) from microalgae biomass is generally low via traditional extraction-conversion route due to the inefficiency in solvent extraction. One of the alternatives to overcome the limitations of conventional extraction-conversion process is the ‘in situ’ transesterification method in which the lipids are simultaneously extracted and converted to FAME.

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.