ForestERW: a spatially explicit carbon dioxide removal model for practical enhanced rock weathering applications in United States forests

Enhanced rock weathering (ERW) is an emerging carbon dioxide removal (CDR) pathway that has been heavily explored for agricultural systems. There may also be co-benefits from this approach in historically acidified forest ecosystems by replenishing depleted nutrient cations, leading to increased tree growth. However, far less analysis has been conducted for forest land applications. Process-based modeling of these benefits is currently preferable because there are insufficient empirical data on ERW in forests to effectively capture the spatial heterogeneity in climate, soils, and geology across the U.S. We developed and calibrated a mechanistic model that simulated a single 40 tonne per hectare basalt application rate across 132 million hectares of practically manageable forested land within the conterminous United States. The gross CDR potential is 660 Mt CO2e from a single application, annualized to 66.0 Mt CO2e yr−1 over 10 years. Abiotic ERW was geographically dispersed and accounted for 76.6% of the total, while biotic ERW accounted for 23.4% and was clustered in the Pacific Northwest and the East. After carbon penalties were assessed, using a life cycle assessment, the net CDR potential is 353 Mt CO2e from a single application (35.3 Mt CO2e yr−1 over 10 years), with opportunities to increase net sequestration through reapplication. In this study we provide the first detailed assessment of the potential for ERW in U.S. forests under realistic supply-chain assumptions.