A Comparison of Outdoor Mixed Cultures Versus Monocultures of Nannochloropsis salina and Phaeodactylum tricornutum for Biofuel Application

Abstract

Microalgae have been identified as a potential chemical source for biofuels, but production costs still greatly limit this industry. The purpose of this study was to determine the efficiency of mixed algal cultures containing two species of microalgae, Nannochloropsis salina and Phaeodactylum tricornutum, in comparison to their respective monocultures. The respective microalgae cultures were grown in 557L experimental tanks with harvests performed every 3-7 days, i.e., after growth had reached the stationary phase, for a period of 90 days. Microalgae biomass (g/m2), productivity (g/m2/day), and nutrient utilization were analyzed with respect to treatment and different temperatures. The average biomass of the mixed culture treatment (39.81 g/m2) was significantly (p=1.04 x 10-5) greater compared to the P. tricornutum monoculture treatment (35.57 g/m2) but was not significantly different from the N. salina monoculture treatment (39.4 g/m2). Observations of biological contamination do not support the hypothesis that contamination would be less in mixed cultures, as this treatment experienced the highest average contamination levels.