Analyzing Co-Benefits and Rock Sourcing in Life Cycle and Techno-Economic Assessment of Enhanced Rock Weathering.

Enhanced rock weathering (ERW) is a carbon dioxide removal (CDR) strategy that stores atmospheric CO2 permanently in carbonates. Recent ERW literature has highlighted potential co-benefits from cropland ERW application, including reduced fertilizer requirements and soil N2O emissions. However, contributions of co-benefits to life cycle environmental impacts remain poorly understood, and methodologies for integrating them into environmental and cost assessments are lacking. We address these research gaps by integrating co-benefits into a coupled life cycle assessment and techno-economic analysis to quantify environmental impacts and costs of ERW with and without co-benefits. We assess both waste and virgin rock sourcing and transportation pathways in the United States. Our results show that cradle-to-farm-gate greenhouse gas (GHG) emissions of ERW, with long-range transport allowing nationwide deployment, range from 44 to 371 kg CO2eq/t CO2eq removal, and costs vary between US$123 and US$926/net t CO2eq removal, depending on rock type, sourcing, and transport mix. Fertilizer and N2O co-benefits can reduce GHG emissions of ERW deployment by 10.4-55.7%, costs by 3.2-7.6%, and other environmental impacts by 1-147%. The contributions of co-benefits are region-dependent, demonstrated by our spatial analysis of croplands across the United States. Our framework presents methodological advancement for CDR assessments and supports future deployment of ERW.