Environmental viability of transition from thermal to SC-CO2 regeneration of activated carbon for climate change mitigation: An LCA-based study

This study evaluates the environmental viability of supercritical CO2(SC-CO2) regeneration as an alternative to conventional thermal regeneration for spent activated carbon(SAC). To identify operating conditions under which SC-CO2 achieves equivalent or superior performance, a series of experiments was conducted by varying key parameters. As a result, 100 bar and 250°C were selected as the representative conditions. Under these settings, SC-CO2 achieved 94–97% pollutant removal efficiency and maintained a carbon loss rate below 1.1% over eight regeneration cycles. A comparative life cycle assessment (LCA) was performed using the EF 3.1 method, with a cradle-to-gate boundary and a functional unit defined as the regeneration of 1 m³ of spent activated carbon. Compared to thermal regeneration, the SC-CO2 process reduced global warming potential (GWP) by 74.9% and showed 80–90% reductions in acidification, eutrophication, and photochemical ozone formation. Methanol use was identified as a key environmental hotspot in the SC-CO2 system. Scenario analysis showed that substituting biomass-based methanol and implementing a 60% solvent recovery system could further reduce GWP by 6.7% and 41%, respectively. These findings confirm that SC-CO2 regeneration is not only technically feasible but also environmentally superior, supporting its role as a low-carbon, circular alternative to thermal regeneration.