Large-scale CO2 removal by enhanced carbonate weathering from changes in land-use practices

Continental rock weathering exerts a negative feedback on global warming by removing atmospheric CO2. Carbonate weathering contributes most of the dissolved inorganic carbon measured in inland waters, chiefly as HCO3-, though carbonate rock covers only a minor proportion of continental surface (-15%). The fast kinetics of carbonate weathering leads the trace carbonate to contribute greater HCO3- loads than silicate even in silicate catchments. Thus, the uses of carbonate powders on continental surface with silicate via agricultural liming can potentially enhance the CO2 removal. Here, using an equilibrium modeling approach and results of the CMIP6 GCM model, we estimate the actual total CO2 removal (ATCR) by the weathering of both carbonate bedrock and carbonate-rich soils, at the global scale. The potential CO2 removal (PCR) which can be achieved by spreading carbonate powders on non-carbonate lands is also estimated. The results show that the ATCR at present is approximately 0.166 Gt yr(-1), which is similar to the previous result estimated from the global river data base. The PCR is 0.843 Gt yr(-1), five times the ATCR. Future climate and land-use changes may strongly increase the ATCR. Therefore, we suggest that carbonate weathering enhancement by land-use changes can potentially help mitigate the current climate trends.

Automated summary

Continental rock weathering removes atmospheric CO2 and contributes dissolved inorganic carbon in inland waters. Agricultural use of carbonate powders can enhance CO2 removal. The actual CO2 removal by weathering is estimated to be 0.166 Gt yr(-1), while the potential removal achieved by spreading carbonate powders on non-carbonate lands is 0.843 Gt yr(-1).