Direct measurement of carbon dioxide removal due to enhanced weathering

Enhanced weathering (EW) is a durable carbon removal strategy with clear pathways to produce significant global supply on a decadal scale. Despite increasing interest and investment in this process, there have been limited direct, continuous observations of instantaneous carbon removal rates from feedstock dissolution. In this study, we monitor a soybean plot amended with basalt in Southeast Virginia using continuous in-soil CO2 monitors, a method not previously applied in agricultural EW trials. We provide clear evidence of CO2 flux reduction within the soil profile, equivalent to 1.04 tCO2/ha/yr. This removal is most substantial in the growing season, following significant rain pulses. This work supports that direct, continuous gas-phase measurements could play an important role in advancing our understanding of biotic and abiotic influences on enhanced weathering rates, and demonstrating enhanced weathering to be a rigorous, scalable method of durable carbon removal.