Uncertainties of enhanced rock weathering for climate-change mitigation

Enhanced rock weathering (ERW) on agricultural soils is under consideration as a long-term carbon dioxide removal (CDR) strategy. In this Perspective, we evaluate uncertainties related to ERW around feedstock availability, plant–soil system impacts, CDR efficiency along the land–ocean continuum and socio-economic considerations. The composition of (ultra)mafic rocks places constraints on the availability of suitable feedstock when considering their potential for CDR and toxic element contents. For ERW application at scale, dedicated mining for suitable feedstock seems unavoidable. ERW can positively and negatively affect soil structure, hydrology, and overall carbon and nutrient cycles, and so optimal ERW will require site-specific assessment of effective CDR and mitigation of potential negative impacts. Additionally, the fate of weathering products along the land–ocean continuum in rivers remains poorly constrained, which is a challenge for verifying successful CDR. The socio-economic effects and constraints of ERW regarding financing and risk responsibility are also uncertain. Ultimately, large-scale ERW deployment seems limited by substantial challenges throughout its application, from its initial set-up to final CDR. Future research prioritizing site-specific assessments, long-term monitoring along the land–ocean continuum, and system modelling to constrain uncertainties and address socio-economic factors is needed to ensure that ERW deployment is effective, equitable, and sustainable.