Objective and Method CO₂ sequestration in basalts offers advantages such as permanent carbonation and elevated safety. Based on literature review and case studies, this study compared the CO₂ sequestration performance of basalts, clastic rocks, and carbonate rocks. Accordingly, the pros and cons of technologies for CO₂ sequestration in these rocks were determined, and the dominant mechanisms underlying the CO₂ sequestration were identified. By revealing the characteristics of CO₂ sequestration in the three rock types based on representative projects and tests, this study conducted a comparative analysis of the mechanisms, conditions, technologies, potential, and siting for CO₂ sequestration in the three rock types.

Results and Conclusions CO₂ sequestration in basalts was dominated by mineral trapping. Specifically, the abundant Fe²⁺, Ca²⁺, and Mg²⁺ ions in basalts can rapidly react with CO₂ to form stable carbonate minerals, offering the advantages of long-term and stable CO₂ sequestration. A representative project is CarbFix of Iceland, which injects acidic solutions formed by CO₂ dissolution in water into basalt strata to simulate and accelerate the natural weathering process of basalts. Regarding siting for CO₂ sequestration in basalts, it is necessary to avoid tectonically unstable areas such as seismic zones and active faults. Given that basalts are extensively distributed globally and that their tight structures and structural trapping can reduce the CO₂ leakage risk, CO₂ sequestration in basalts exhibits significantly elevated safety and permanence compared to traditional methods. Nevertheless, this technology faces three key challenges: huge water consumption, geological complexity, and low sequestration efficiency. Regarding water consumption, 25 t of freshwater is required when injecting 1 t of CO₂ using a traditional method, exacerbating resource conflicts in regions with water scarcity and incurring high costs of water transfer. Although seawater acts as a potential alternative, it is prone to cause pipeline corrosion and formation clogging due to its high salinity, with resulting environmental risks remaining poorly understood. In terms of geological complexity, the uneven distribution of fractures and pores in basalts leads to significant differences in CO₂ diffusion and mineral trapping efficiency while also potentially increasing the CO₂ leakage risk. However, existing geological modeling techniques are insufficient for the accurate prediction of actual conditions. Regarding sequestration efficiency, carbonate minerals generated from mineral trapping in basalts will cover the surfaces of active minerals, reducing reaction rates and creating a passivation effect. This issue can be mitigated by injecting nanocatalysts or using ultrasound-assisted techniques.