What is the maximum potential for CO2 sequestration by “stimulated” weathering on the global scale?
Natural chemical weathering of silicate rocks is a significant sink for soil and atmospheric CO2. Previous work suggested that natural chemical weathering may be stimulated by applying finely ground silicate rocks to agricultural areas or forests [stimulated weathering (SW)]. However, it remained unknown if this technique is practical to sequester globally significant amounts of CO2 under realistic conditions. Applying first estimates of “normal treatment” amounts from a literature review, we report here a theoretical global maximum potential of 65 106 t sequestered C a−1 if SW would be applied homogenously on all agricultural and forested areas of the world. This is equivalent to 0.9% of anthropogenic CO2 emissions (reference period 2000–2005). First, however, the assumed application of SW on most of the considered areas is not economically feasible because of logistic issues, and second the net-CO2 sequestration is expected to amount to only a fraction of consumed CO2 due to the energy demand of the application itself (currently ~11%). Unless progress in application procedures is provided, the recent realistic maximum net-CO2-consumption potential is expected to be much smaller than 0.1% of anthropogenic emissions, and the SW would thus not be one of the key techniques to reduce atmospheric CO2 concentration. However, literature suggests that for some agricultural areas (croplands) and specifically for rice production areas in humid climates, this SW may be a feasible tool to support international efforts to sequester CO2. SW may be cost effective for those areas if linked to the CO2-emission certificate trade in the future, and increases in crop production are taken into account.