Enhanced weathering for CO2 removal from a global perspective

Enhanced weathering (EW) has the potential for CO2 removal, which has become a necessary measure to mitigate anthropogenic climate change. However, as a relatively new concept and technology, the current academic understanding of EW is not very clear. Here, we compared the C-sequestration potential of different silicate materials, estimated the global distribution and net C-footprint of basalt, and assessed the worldwide EW potential using a global silicate-rock dataset (n = 9088). Results showed that basalt had a moderate maximum C-sequestration potential ( R_CO₂ = 0.30 ± 0.08) and chemical weathering intensity (CIA = 61.48 ± 13.16), which could be regarded as the most promising material for EW. Using life cycle assessment, we calculated the net C-footprint of basalt over 50 years. As the acidity increased, the C-sequestration efficiency of EW was enhanced. When the pH was 4, it exhibited the highest C-sequestration efficiency at a particle size of 10 μm. Based on temperature, precipitation, and soil pH, we estimated global EW potential in croplands. With an application rate of 40 t ha−1 in croplands, the theoretical C-sequestration was approximately 18.84 Gt CO2 globally. Regions with favorable EW potential included Southern Asia, Southeast Asia, Latin America, and West-Central Africa. Basalt is mainly distributed in India, Ethiopia, Russia, Iceland, Brazil, and along the western coast of the American continent, which serves as a guide for sourcing materials locally to implement EW. Effective EW requires balancing various approaches, including grinding, material and external-environment selection, and local sourcing. Future work requires interdisciplinary researches to evaluate adverse effects and safety concerns of EW. Although EW cannot replace emissions reductions, our assessment lays a theoretical foundation for EW as a means to help achieve the global net-zero targets by 2050.