Strategies for enhancing microalgal carbon sequestration: a review on strain development, culture system optimization, parameter control, and metabolic engineering

The microalgae-mediated carbon capture and utilization (CCU) technology demonstrates significant advantages and application potential compared to traditional carbon sequestration technologies by coupling CO₂ sequestration with biomass valorization. Theoretical calculations show that large-scale microalgae cultivation on 13 million acres of land can achieve an annual CO₂ fixation capacity of approximately 50 million tons while simultaneously producing over 3 million tons of biomass. However, the practical application of microalgae currently faces two major obstacles: the relatively low efficiency of photosynthetic CO₂ fixation and the high cost of microalgal cultivation processes. This review summarizes the research progress on strategies to improve the carbon sequestration efficiency of microalgae. Studies indicate that after optimization, the CO₂ fixation rate of microalgae has reached 0.07–1.5 g L⁻¹ d⁻¹, highlighting its considerable carbon sink potential. Additionally, techno-economic analysis and life cycle assessment reveal microalgal cultivation as the main cost component and fossil fuel-based power emissions as the primary global warming contributors. Finally, current challenges in microalgal carbon sequestration are discussed, and future efficiency-enhancing directions are proposed from multiple perspectives. This review aims to provide valuable references for improving carbon sequestration and biomass production.