Optimized accumulation of algal lipids for bio-jet fuel production

Abstract

Civil aviation sector faces the enormous challenge of becoming carbon neutral by 2050, while the sector is rapidly growing despite the drawbacks of COVID-19. The sector aims to reduce its carbon emissions and encourages sustainable aviation fuels. Microalgae stands out as a third generation biobased feedstock for an alternative sustainable jet-fuel production as microalgae cultivation does not need arable area, produce respectable amounts of biomass in limited time periods and does not compete with other food and energy crops. In this study, three different oleaginous green microalgae species were cultivated under 23 different conditions, and their biomass, lipid, and fatty acid methyl ester (FAME) productivities were evaluated to optimize microalgal lipids suitable for bio-jet fuel. Changes in biomass and lipid contents were observed by applying nitrogen deprivation in different culture media. Nannochloropsis gaditana grown in Algal medium and Ettlia oleoabundans in MB3N medium were scaled-up to 15000L cultures under nitrogen-replete conditions to observe the changes in biomass and lipid content in outdoor open ponds respectively. N. gaditana reached the highest biomass (1.53 g/L) and lipid productivity (0.72 g/L) in Algal medium. Nannochloropsis sp. had the highest FAME productivity (363.2 mg/L), transesterifiable lipid percentage (67.7% of lipid dry weight) and FAME percentage in biomass (35.1% of dried biomass) in f/2 medium under nitrogen deprivation. Lipid extraction efficiency and FAME profile changes of different pretreatment and cell disruption methods were compared. N. gaditana in Algal medium produced eicosapentaenoic acid equivalent to 2.86% dry weight, considered as a biorefinery side product.