Oil assessment of Halamphora coffeaeformis diatom growing in a hybrid two-stage system for biodiesel production

Abstract

The lipid content, composition and productivity of the marine benthic diatom Halamphora coffeaeformis were studied in order to evaluate its potential as feedstock for biodiesel production. Cultures were carried out in two stages: I) in photobioreactors (PBRs) to increase the biomass as inoculum for larger volumes, and II) in raceway ponds to increase naturally the triacylglycerol (TAG) content during the stationary growth phase. Biomass concentrations of 0.64 g L-1 and 0.23 g L-1 were reached in the PBR and the raceway pond, respectively. Total lipid content was 54.4 (+11.6) % ash free dry weight (AFDW) in the raceway pond on day 19 (harvest day), with a neutral lipid content of 34% AFDW. The TAG productivity in the raceway pond was 1.2 mg L-1 d-1. The indicators of biodiesel, calculated from fatty acid profile composition, showed that H. coffeaeformis oil was of good quality, according to international standards. Some hypothetical aspects are proposed in order to improve lipid productivity and net energy ratio in processes at larger scales.