Weathering of geological materials is well known to capture CO2 from the atmosphere and convert it to mineral carbonates and soluble carbonate and bicarbonate species. Enhancing the rate at which those materials weather will clearly increase the removal of CO2 from the atmosphere. The key knowledge gaps associated with these processes include the magnitude of the realistically achievable impacts, the permanence of those impacts and quantification of impacts resulting from long-term enhanced weathering programs. This CNI-LDRD aims to address these knowledge gaps by focusing on three core objectives: (1) Carefully-designed Experiments to advance understanding of in situ weathering rates; (2) Mechanistic modeling to optimize operational space for enhanced weathering, and (3) Scalability assessment of enhanced weathering and the implications for soil health and climate change policy.