When coupled with direct air or point source capture technologies, CO2 mineralization in oceanic basalts has the capacity to remove enormous quantities of CO2 from the atmosphere or prevent newly produced CO2 from ever reaching it. Predicting mineralization rates and thereby optimizing injection and monitoring efforts presents unique challenges for reactive transport models, including the classic field-lab rate discrepancy – i.e., the concept that reaction rates measured in the laboratory tend to perform poorly when applied at the field scale. In this presentation, we will discuss our recent efforts to constrain and parameterize reaction rates in laboratory experiments with an eye towards improving predictions of mineralization rates at the field scale. We use a combination of gas sorption and neutron scattering measurements to quantify total surface area of basalt cores, and then pair this with backscatter electron imaging (500 nm/pixel) and image processing techniques to calculate mineral-specific surface areas. We combine these values with new experimental measurements of surface area-normalized plagioclase and clinopyroxene dissolution rates, and compare the resultant predictions against effluent chemistry measured in CO2 mineralization experiments conducted on the same cores. The results based on mineral-specific quantifications of surface area are in reasonably good agreement with effluent chemistry, but suggest the potential for introducing significant uncertainties when extrapolating poorly quantified mineral surface areas to the field scale in reservoir-scale reactive transport models. We conclude by demonstrating that, even given the uncertainty in reaction rates, CO2 mineralization in oceanic basalts has the capacity to put a significant dent in the global anthropogenic CO2 budget.

CO2 mineralization in basalt from nanopore to global scales

ACS Spring 2022

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