Marine Microalga <i>Nannochloropsis</i> Cultivation in Pilot-Scale for Sustainable Eicosapentaenoic Acid Production: Economic Viability and Life Cycle Assessment

This study is the first to comprehensively evaluate the economic feasibility and environmental sustainability of scaling up eicosapentaenoic acid (EPA) production through Nannochloropsis cultivation. Results showed that among eight Nannochloropsis species, Nannochloropsis sp. FJNU303 (Nsp-303) was the optimal candidate to achieve the maximum biomass (1.51 g/L), EPA yield (182.23 mg/L), and carbon dioxide (CO2) fixation rate (153.52 mg/(L·d)). Meanwhile, Nsp-303 cultivated in tubular photobioreactors (TB-PBRs) exhibited superior growth performance, EPA yield, and CO2 fixation compared with airlift and flat-panel photobioreactors. Moreover, Nsp-303 cultivated in 700 L (indoor), 2000 L (outdoor), and 10,000 L (outdoor) TB-PBRs revealed that the 2000 L system had the lowest production cost (7.75 USD/kg dry biomass), highest CO2 fixation rate (144.41 mg/(L·d)), and high biomass production (1.13 g/L). Although Nannochloropsis cells in the 10,000 L TB-PBRs exhibited a lower biomass, this cultivation had the potential to reduce costs through economies via scaling up cultivation. Additionally, the results of life cycle assessment revealed that outdoor large-scale TB-PBRs’ cultivation significantly reduced energy consumption, material waste, and nutrient emissions, resulting in an 86.35% reduction in the global warming potential. Overall, this study provided a clear insight into the economic and environmental factors involved in EPA production by pilot-scale cultivation with Nannochloropsis.