Sustainable pathways for CO2 mitigation: A comparative energy, exergy, and economic analysis of optimized post-combustion capture and microalgae-based sequestration

Global warming has become one of the most pressing global challenges in recent years. In response, a range of technologies has been developed to mitigate its effects. One such approach involves burning biogas, which primarily produces carbon dioxide. The goal is to capture this CO₂ to support a sustainable system. One such technology is carbon capture, particularly post-combustion carbon capture (PCC) at the industrial scale. However, conventional PCC configurations are associated with high energy consumption and inefficiencies, such as the lack of integration between the hot and cold sections. In this study, Aspen HYSYS V11 was employed to simulate and analyze three distinct PCC configurations: Lean Vapor Compression (LVC), Solvent Split Flow (SSF), and Rich Solvent Recycle (RSR). These configurations were rigorously evaluated for their energy efficiency and CO₂ capture performance. Additionally, a comparative assessment was conducted between conventional PCC technologies and a bioremediation-based alternative: microalgae cultivation systems, in which CO₂ is absorbed through photosynthetic microalgae growth. This comparative analysis was designed to benchmark the viability of biological carbon sequestration against solvent-driven PCC processes, providing insights into their respective technical and environmental tradeoffs. Furthermore, a comparative analysis based on energy, exergy, and economic performance was presented. In the PCC sector, the results showed that the RSR configuration could increase efficiency by approximately 3 % compared to the conventional configuration, while reducing the overall cost by about 1.30 $/h, bringing the total cost to around 23.28 $/h. When compared with the microalgae plant, the findings were even more significant. The microalgae system demonstrated a high exergy efficiency of about 72.64 % and a substantially lower total cost of approximately 7.17 $/h. These results indicate that the microalgae approach offers considerable advantages over even the optimized PCC configurations.