The impact of enhanced rock weathering on soil organic carbon

Terrestrial enhanced rock weathering (ERW) is a geoengineering technique that amends soils with crushed magnesium (Mg) and calcium (Ca) rich silicate rock to accelerate carbon dioxide removal (CDR) with the production of dissolved and solid carbonates. Although ERW is projected to store large amounts of inorganic carbon, up to 2 Pg carbon (C) per year (Beerling et al., 2020), significant uncertainty surrounds ERW research, with a critical question remaining as to how ERW affects soil organic carbon (SOC), the largest terrestrial C reservoir with 1550 Pg C globally. While increases to SOC after crushed rock additions could increase the carbon removal capacity of ERW, reductions in SOC could negate its benefits. Field-scale ERW studies examining SOC dynamics, remain few. Sokol et al. (2023), found that ERW can destabilize organic carbon, making a seemingly stable pool vulnerable to decomposition. Conversely, Xu et al. (2024) reported SOC increases four to eight times higher than soil inorganic carbon (SIC) growth in oxisols after CaSiO₃ amendments. These studies highlight that the effect of ERW on SOC is influenced by soil properties. I will address this gap in knowledge by gaining a comprehensive understanding of ERW’s impact on SIC and SOC pools across ten agriculturally relevant soils in the US with unique soil properties that have been previously taken from all major US ecosystems and climate zones (Davenport, 2024). My study involves a one year incubation assessment that leverages exploration of outcomes across a broad soil gradient under a controlled environment. My findings will elucidate what conditions (i.e., soil properties, climate) will lead to the greatest mitigation impact for targeting ERW deployments.