Vienne et al. (2026): River alkalinity enhancement for scalable and energy-efficient geochemical carbon dioxide removal: potential, costs and risks?
Arthur Vienne, Tom Cox, Harun Niron, Tim Jesper Suhrhoff and Sara Vicca, IN: CDR.Xiv (Preprint), https://doi.org/10.70212/cdrxiv.2026539.v1
Gigaton-scale carbon dioxide removal (CDR) from the atmosphere will be necessary to limit global warming to below 2 C. Current approaches, such as afforestation or biochar, are constrained by land and biomass availability, whereas direct-air carbon capture technologies are energy-intensive and costly. Here, the authors discuss river alkalinity enhancement (RAE), a geochemical carbon dioxide removal strategy that uses readily available limestone (CaCO₃) and derived slaked lime (Ca(OH)₂) to increase alkalinity in rivers. Unlike the direct addition of these minerals to the ocean, which is currently restricted by the London protocol, addition of alkalinity to rivers is already commercially applied in some regions and alkalinity dosing can be monitored in controlled systems. Controlled rock dissolution in ponds allows for direct measurement of CO₂ removal prior to water release back into rivers, enhancing traceability and verification.They simulate CO₂ uptake in 149 major rivers, considering river flows and chemistry and life-cycle emissions from mining, grinding and transporting rock and pumping water in reactor ponds.