Microalgae for biofuel production: a critical assessment of technologies, environmental performance, and scale-up challenges

Microalgae represent promising feedstocks for biofuel production due to their rapid growth rates, high lipid content, and superior biomass yields compared to terrestrial crops. This critical assessment examines the technological pathways, environmental performance, and scale-up challenges of microalgae-based biofuel production systems. The review systematically analyses cultivation methods (including open ponds and photobioreactors), harvesting techniques, and conversion processes (thermochemical and biochemical) currently employed in microalgae biofuel production. Environmental performance analysis reveals microalgae's potential for greenhouse gas mitigation through carbon dioxide fixation during cultivation, though life cycle assessments indicate that energy-intensive dewatering and processing steps remain significant barriers to sustainability. Despite theoretical advantages, commercial-scale production faces persistent economic challenges related to high operational costs, energy requirements, and capital investments. The assessment identifies key technological bottlenecks requiring innovation: improving lipid productivity through strain selection and optimisation, developing energy-efficient harvesting and dewatering processes, and integrating biorefinery approaches to valorise co-products. By evaluating these interdependent factors, this review provides a comprehensive framework for researchers, industry stakeholders, and policymakers to advance the development of economically viable and environmentally sustainable microalgae biofuel production systems.