Integrated algal systems for industrial CO₂ mitigation: advances, challenges, and prospects in environmental biotechnology.

Carbon dioxide (CO₂) constitutes approximately two-thirds of total anthropogenic greenhouse gas emissions and therefore represents the primary target for mitigation strategies. Among the available approaches, algal-based CO₂ capture has emerged as a promising biological option due to the high photosynthetic efficiency, rapid growth rates, and capacity of microalgae to utilize concentrated CO₂ streams directly from industrial point sources. Under optimized laboratory and pilot-scale conditions, algal systems have been reported to achieve CO₂ fixation rates in the range of approximately 0.1-1.5 g CO₂ L^-1 d^-1, corresponding to areal biomass productivities of roughly 10-40 g m^-2 d^-1, depending on species, reactor configuration, and environmental conditions. This review critically evaluates the potential of algal-based systems for CO₂ biofixation, with particular emphasis on algal carbon assimilation mechanisms, cultivation strategies, and operational constraints relevant to large-scale deployment. Key parameters influencing CO₂ capture efficiency, including light irradiance, pH, nutrient availability, and gas-liquid mass transfer are systematically discussed. The role of algal-bacterial consortia in enhancing carbon utilization and enabling integration with wastewater treatment processes is also examined. Furthermore, the review compares open and closed cultivation systems, highlighting trade-offs among productivity, energy demand, contamination risk, and economic feasibility. While emerging approaches such as hybrid cultivation concepts and process-intensification strategies offer pathways to improve system performance, their practical implementation remains constrained by downstream processing costs and scale-up challenges. Overall, the analysis suggests that algal-based CO₂ mitigation is most effective when deployed as part of integrated biorefinery frameworks, particularly in conjunction with wastewater treatment and value-added biomass utilization-rather than as a standalone carbon sequestration solution. This integrated perspective provides a balanced assessment of the opportunities and limitations of algae-based CO₂ mitigation within sustainable climate and environmental management strategies.

© 2026. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.