Methodology shapes the greenhouse gas mitigation potential of post-combustion CO2 capture: Insights from evaluation metrics and sensitivity analysis

The contribution of post-combustion CO 2 capture (PCC) to reducing greenhouse gas (GHG) emissions has been widely studied; however, differences in system boundaries and evaluation metrics hinder consistent comparisons across studies. Here, we analyzed GHG emissions from fossil-fueled power plants by systematically varying the system boundaries and functional units. Two bases were considered: electricity production and captured CO 2 . On the electricity basis, PCC retrofits reduced cradle-to-gate GHG emissions by approximately 50% compared with benchmark cases, thereby clarifying the mitigation potential across power systems. On the captured CO 2 basis, gate-to-gate accounting with direct CO 2 emissions revealed PCC could not achieve 70% of GHG emissions reduction in case of 90% of CO 2 capture rate due to additional utility consumption for CO 2 capture. Cradle-to-gate results clarified the relation between CO 2 capture and the energy transition. Of note, in decarbonized grid electricity scenario, PCC with liquified natural gas (LNG)-fired systems had worse cradle-to-gate GHG emissions than other systems due to unavoidable indirect emissions associated with LNG supply, resulting in 0.68 kg-CO 2 emit/kg-CO 2 cap. This study underscores the importance of appropriate boundaries and evaluation metrics and when evaluating PCC and provides guidance for the consistent assessment of CO 2 emission reduction technologies for carbon neutrality.