Effect of Nitrogen Source in Low-Cost Media on Biomass and Lipid Productivity of Nannochloropsis salina for Large-Scale Biodiesel Production

A major cost component for large-scale algal cultivation is the medium. In this study, a significantly higher growth rate was found for Nannochloropsis salina in an inexpensive medium of seawater and agricultural fertilizer than was reached in the f/2 medium. A key difference between this new low-cost medium and the f/2 medium is the nitrogen source. In the conditions tested herein, with aeration using air, biomass productivity reached 0.5496 g L-1 day(-1) after 10 days in the low-cost medium compared with 0.1215 g L-1 day(-1) in the f/2 medium. The lipid productivity of algae grown in the low-cost medium was also higher than that in the f/2 medium (0.1281 g L-1 day(-1) versus 0.0432 g L-1 day(-1)). The strong linear correlation (R-2=0.9721) between chlorophyll content and biomass concentration demonstrated that this new medium can support healthy and consistent growth of algal cells. The results suggest that it would be preferable to feed the algae for large-scale biodiesel production with agricultural waste stream or untreated swine wastewater containing high levels of ammonia rather than treated effluent in which the ammonia/urea has been oxidized to nitrate. (c) 2014 American Institute of Chemical Engineers Environ Prog, 34: 297-303, 2015