Concomitant Mineral Carbonation and CO2 Reduction in Short-Term Water-Basalts Reaction: Difference Between Basaltic Glass and Basaltic Crystals.

Carbon capture and storage (CCS) technology aims to decrease atmospheric carbon dioxide (CO2) levels. Subsurface mineral carbonation is the safest method of CCS, where water-dissolved CO2 is injected into the subsurface and reacts with mafic or ultramafic minerals that release cations (Ca2+, Mg2+, Fe2+), resulting in the formation of carbonate minerals. However, more research is needed to effectively implement CCS in basaltic reservoirs. In these experiments, it is shown how two different samples (basaltic glass and basaltic crystals) react to carbonation under identical conditions: a pH of around 6.5, reaction times of 2 and 5 days, temperatures of 100°C and 200°C, and absolute pressures from 70 to 85 bar(a) at the operating temperatures. The results show partial dissolution of mineral phases, formation of new alteration phases, and carbonate precipitation. This study aims to identify key variables to analyze in such experiments to evaluate the formation of CO and CH4 as an alternative reaction pathway during mineral carbonation of injected CO2 in basalts. Ultimately, this research aims to lay the groundwork for future studies on basalt carbonation and on how the CCS process might be influenced by CO2 reduction to CO and CH4.