A holistic overview of the in-situ and ex-situ carbon mineralization: Methods, mechanisms, and technical challenges

To mitigate anthropogenic CO₂ emissions and address the climate change effects, carbon capture and storage by mineralization (CCSM) and industrial mineral carbonation are gaining attraction. Specifically, in-situ carbon mineralization in the subsurface geological formations occurs due to the transformation of silicate minerals into carbonates (e.g., CaCO₃, MgCO₃) while ex-situ carbon mineralization at the surface undergoes chemical reactions with metal cations - thus leading to permanent storage. However, both processes are complex and require a rigorous investigation to enable large-scale mineralization. This paper, therefore, aims to provide an overreaching review of the in-situ and ex-situ methods for carbon mineralization for different rock types, various engineered processes, and associated mechanisms pertinent to mineralization. Furthermore, the factors influencing in-situ and ex-situ processes, e.g., suitable minerals, optimal operating conditions, and technical challenges, have also been inclusively reviewed. Our findings suggest that in-situ carbon mineralization, i.e., subsurface permanent storage of CO₂ by mineralization, arguably is more promising than ex-situ mineralization due to energy efficiency and large-scale storage potential. Furthermore, the effect of rock type can be ranked as igneous (basalt) > carbonates (sedimentary) > sandstone (sedimentary) to consider for rapid and large-scale CCSM. The findings of this review will, therefore, help towards a better understanding of carbon mineralization, which contributes towards large-scale CO₂ storage to meet the global net-zero targets.