Integrated Carbonate-Based CO2 Capture—Biofixation through Cyanobacteria

Microalgae, renowned for their high photosynthetic efficiency and minimal competition with land-based crops, hold great promise in the biofixation of CO2 from waste sources, making them valuable for diverse applications, including biofuels, food production, and biomaterials. An innovative technology, the integrated carbonate-based carbon capture and algae biofixation system is emerging as an alternative to traditional carbon capture and sequestration (CCS) methods. This closed-loop system utilizes bicarbonates as inorganic carbon sources, which can directly enter microalgae photosynthesis, subsequently regenerating carbonates for another cycle of carbon capture. This system offers significant advantages, including cost savings in carbon supply, simplified photobioreactor development, and reduced labor and energy requirements. Nevertheless, further research is essential to evaluate the suitability of various microorganisms and search for optimal growth conditions. In this study, we assessed the performance of two strains of Spirulina within the integrated system. Employing a Design of Experiments approach, we simultaneously varied temperature, bicarbonate concentration, and light irradiation while operating within a lab-scale photobioreactor. We achieved remarkable results, with a biomass productivity of 875 mg/L·d and an impressive CO2 utilization efficiency of 58%. These findings indicate a genuine opportunity for further exploration and scaling of this approach in industrial settings.