Comparative techno-economic and life cycle assessment of microalgae-based CO2 capture technologies for coal-fired power plants under different carbon supply modes

Integrating microalgae cultivation with carbon capture from coal-fired power plants is a promising decarbonization strategy, but its viability is often hindered by the high energy penalty of conventional CO2 capture processes. This study introduces and evaluates a novel hybrid chemical absorption–microalgae conversion (CAMC) process designed to overcome this barrier. The key innovation of the CAMC route is the replacement of the energy-intensive thermal desorption unit with the microalgae cultivation system itself, enabling simultaneous solvent regeneration and carbon bio-fixation. To quantify its advantages, the CAMC process was benchmarked against two conventional pathways for a 500 MW coal-fired power plant: (i) post-combustion chemical absorption coupled with cultivation, and (ii) direct flue gas injection. The results demonstrate that the CAMC hybrid process, particularly when paired with open pond systems, is the superior pathway. It achieved a low energy intensity (2.31 MJ/kg biomass), a highly favorable economic cost (0.69 USD/kg biomass), ad substantial net-negative emissions (−345 kg CO2-eq/ton biomass). This performance significantly surpassed the conventional capture pathway, which suffered from a high carbon footprint, and proved more cost-effective and productive than the direct flue gas approach. To enable large-scale deployment, future efforts should prioritize enhancing algal productivity and integrating renewable energy and low-carbon nitrogen sources. In summary, the CAMC process represents a technically viable and economically promising innovation capable of achieving deep decarbonization in fossil-based power generation.