Suitability of rocks, minerals, and cement waste for CO2 removal via enhanced rock weathering

Mineral and rock additions to the environment have been proposed as a pathway to remove atmospheric CO2. This process occurs when hydrated minerals or rocks increase alkalinity, promoting the formation of bicarbonate. In this study, we evaluate the potential of commonly used hydrated rock and mineral powders to enhance alkalinity and react with both atmospheric and concentrated CO2. Silicate minerals and rocks exhibit minimal reactivity with atmospheric CO2 and provide moderate alkalinity enhancement. Volcanic rocks like basalt were shown to release CO2. Ground cement and Mg(OH)2, refined from CO2-free ultramafic rock, significantly increase alkalinity and mineralize both atmospheric and concentrated CO2. However, the effectiveness of cement waste is limit by its variable CaO content and potential heavy metal contributions. Overall, Mg(OH)2, derived from silicates, offers a promising pathway for the removal and storage of CO2. CO2 capture through enhanced rock weathering requires that rock and mineral soil additions promote CO2 to bicarbonate transformation, typically by increasing substrate alkalinity. Here, the authors evaluate the potential of commonly used hydrated rock and mineral powders such as cement waste to enhance alkalinity and react with both atmospheric and concentrated CO2.