Life Cycle Assessment of retrofitting coal and natural gas power plants with a novel CO2 capture technology.

While renewable energy sources are expected to lead decarbonisation efforts in the power sector, carbon capture and storage (CCS) is a viable solution to address remaining fossil emissions for the foreseeable future. Emerging technologies aim to improve the performance of traditional absorption systems at low concentrations. AirPure uses a micro-mixing device to produce CO2 hydrates offering promising opportunities for efficient CO2 capture and transport under mild conditions. This study evaluates its environmental performance on retrofitting power plants producing slurry of CO2 hydrates to identify benefits and trade-offs and support process design. A Life Cycle Assessment (LCA) of the supply of 1 MWh to the grid from coal and gas-fired power plants with and without AirPure retrofit and under different operational contexts, including different transport options, is carried out. Lifecycle CO2eq emissions are significantly reduced for both coal (82-90 %) and gas (62-67 %) plants. Coal plant achieved lower emissions (110-190 kg CO2eq/MWh) compared to gas plant (180-210 kg CO2eq/MWh). With nitrogen oxides co-capture, it could reduce terrestrial acidification, tropospheric ozone formation, and particulate matter for cases with lower post-capture impacts (e.g. short transport distances and renewable power usage). However, the additional energy, particularly for AirPure and ship transport, and AirPure's high water consumption (8 tonnes water/tonne CO2) are significant trade-offs. The findings indicate that AirPure can effectively reduce the global warming potential of fossil fuel power plants and potentially offer co-benefits. Despite the larger volumes of the slurry of hydrates compared to traditional high-dense gas phases, the impact of post-capture processes is generally low, except for long-distance ship transport. Further research is needed on contaminants in hydrate formation and conditions for hydrate injection. Exploring alternative process designs with water recycling or integrated desalination with hydrate dissociation is essential to reduce its consumption or even to mitigate it while creating another relevant co-benefit.