CO2 Mitigation via Capture and Chemical Conversion in Seawater

A lab-scale seawater/mineral carbonate gas scrubber was found to remove up to 97% of CO2 in a simulated flue gas stream at ambient temperature and pressure, with a large fraction of this carbon ultimately converted to dissolved calcium bicarbonate. After full equilibration with air, up to 85% of the captured carbon was retained in solution, that is, it did not degas or precipitate. Thus, above-ground CO2 hydration and mineral carbonate scrubbing may provide a relatively simple point-source CO2 capture and storage scheme at coastal locations. Such low-tech CO2 mitigation could be especially relevant for retrofitting to existing power plants and for deployment in the developing world, the primary source of future CO2 emissions. Addition of the resulting alkaline solution to the ocean may benefit marine ecosystems that are currently threatened by acidification, while also allowing the utilization of the vast potential of the sea to safely sequester anthropogenic carbon. This approach in essence hastens Nature's own very effective but slow CO2 mitigation process; carbonate mineral weathering is a major consumer of excess atmospheric CO2 and ocean acidity on geologic times scales.