Marine Microalgae as a Biorefinery Platform: Cultivation, Lipid Extraction, and Bioenergy Conversion

Abstract

Abstract: Marine microalgae are being investigated as feedstocks for biofuel and bioproduct production because many marine taxa can accumulate lipids while being cultivated in seawater or saline media, reducing dependence on freshwater resources. However, the economic and environmental performance of marine microalgal biorefineries depends strongly on biomass productivity, lipid content, cultivation conditions, harvesting requirements, downstream energy demand, and co-product recovery. Although recent studies have examined cultivation, lipid recovery, and fuel conversion, they often discuss these advances separately, making it difficult to assess the marine microalgal biorefinery as an integrated system. This review examines peer-reviewed studies published between 2020 and 2025 that cover the full production pathway, from species selection and cultivation to lipid extraction, bioenergy conversion, and sustainability assessment. The review focuses on marine genera such as Nannochloropsis, Tetraselmis, and Phaeodactylum tricornutum, as well as cultivation strategies including open ponds, photobioreactors, hybrid systems, low-cost media, and two-phase protocols that enhance lipid accumulation under abiotic stress while maintaining satisfactory biomass productivity. The review also compares open raceway ponds and closed photobioreactors, summarizes recent developments in harvesting and lipid extraction technologies, and evaluates findings from techno-economic analyses and life-cycle assessments. Across the published literature, harvesting, dewatering, and downstream processing are major contributors to energy consumption and production costs, limiting large-scale commercialization. By integrating evidence from upstream cultivation and downstream processing, this review identifies current knowledge gaps and highlights research priorities that could improve the technical, economic, and environmental performance of marine microalgal biofuel production.