Estimating Carbonation Efficiency and Sequestration Rate in Deccan Basalts

The need for rapid, permanent CO2 storage strategies in basalt is critical for climate mitigation given rising global emissions. The first-order estimates suggest significant geological CO2 storage potential in Indian basalts of up to 316 Gt; however, scientific gaps persist in understanding mineral carbonation dynamics, particularly regarding kinetic variation and mineral efficiency on short time scales. This study targets these gaps by systematically quantifying carbonation efficiency and sequestration rates in the Deccan Volcanic Province basalts at 25 bar and 50 °C, analyzing variation across 30- and 60-day intervals. An integrated methodology included rigorous preinjection mineralogical characterization (optical microscopy, XRD, XRF) followed by controlled CO2-water-basalt reactions in fabricated pressurized reactors. The reaction was monitored by using ICP-MS and TGA to determine precise rates of elemental dissolution and carbonate formation. From 30 to 60 days, the carbonation efficiency of Ca increased markedly from 34.62% to 61.76%, that of Mg from 16.36% to 19.74%, and that of Fe from 11.25% to 15.83%, culminating in a total carbonation efficiency jump from 55.22% to 77.28% from 30 to 60 days. Furthermore, over time, the sequestration rates increased from 160.03 to 252.15 g CO2/kg basalt, driven by sustained mineral dissolution and secondary carbonate precipitation, as captured by direct SEM-EDS and confirmed by TGA. Notably, data reveal that reaction proceeds forward due to increasing pH, increasing mineral surface accessibility, and favorable fluid composition result in significant efficiency gains over 60 days, with further improvements probable on extended time scales. The novelty of this study lies in real-time, multiscale tracking of both elemental and total carbonation performance under laboratory conditions, thereby providing scalable, permanent CO2 storage technology deployment.