Biased selection and incomplete characterization of feedstock materials in enhanced rock weathering experiments

Terrestrial Enhanced Rock Weathering (ERW) – the application of crushed rocks to soils to accelerate CO 2 removal – has emerged as a promising climate mitigation strategy to complement emission reduction efforts. One of the key factors controlling the efficacy of ERW is the composition of the utilized rock powder, ultimately constraining the achievable CO 2 removal potential and rate in a given environment. In this article, we highlight that experimental research on ERW is dominated by a narrow range of commercially available rock powders, arguably often selected more for convenience than for relevance. These materials are often poorly characterized, neglecting core methods and principles of petrography. In combination, these shortcomings are detrimental to our understanding of ERW's potential and our ability to guide its successful implementation. We call for a systematic and detailed evaluation of all potential feedstocks, going beyond readily available products. In doing so, we hope to better constrain experimental results and inform on ERW's overall CO 2 removal capacity. • Most enhanced weathering studies use a narrow range of poorly characterized rocks. • These shortcomings limit our ability to accurately assess enhanced weathering. • We call for the assessment of a wider range of rigorously characterized rock types.