Field Validation of Supercritical CO₂ Reactivity with Basalts

Continued global use of fossil fuels places a premium on developing technology solutions to minimize increases in atmospheric CO₂ levels. CO₂ storage in reactive basalts might be one of these solutions by permanently converting injected gaseous CO₂ into solid carbonates. Herein, we report results from a field demonstration in which ∼1000 metric tons of CO₂ was injected into a natural basalt formation in eastern Washington state. Following post-injection monitoring for 2 years, cores were obtained from within the injection zone and subjected to detailed physical and chemical analysis. Nodules found in vesicles throughout the cores were identified as the carbonate mineral, ankerite Ca­[Fe,Mg,Mn]­(CO₃)₂. Carbon isotope analysis showed the nodules are chemically distinct compared with natural carbonates present in the basalt and in clear correlation with the isotopic signature of the injected CO₂. These findings provide field validation of rapid mineralization rates observed from years of laboratory testing with basalts.