Life cycle assessment of CaO looping versus amine-based absorption for capturing CO2 in a subcritical coal power plant

Cradle-to-gate life cycle assessment was used to compare the environmental impact of capturing CO2 from the flue gases in a subcritical coal power plant by using three technologies, namely, absorption with two types of amine processes (Econamine and Econamine FG+) and CaO looping. The results were benchmarked against the same power plant with no capture unit. The intended application of the study is to evaluate whether CaO looping can be an alternative to conventional chemical absorption by amine-based processes for capturing CO2. The inclusion of the CO2 capture unit showed a net reduction only in those impact categories directly associated with the reduction of CO2 as flue gas emissions, i.e. climate change, particulate matter and terrestrial acidification. Emissions for the Climate Change category were 0.33, 0.27 and 0.26 kg CO2-eq/kWh for the two amine based systems (Econamine and Econamine FG+, respectively) and the CaO looping capture unit, thereby reducing the emissions of the same plant without a capture unit (0.96 kg CO2-eq/kWh). Consequently, with the assumptions and system boundaries defined in this study, the CaO looping is a viable alternative to amine-based systems from the environmental point of view. However, taking into account that CaO looping is a process still under development, additional research and process scale-up is necessary to confirm this result.