Microbially-enhanced silicate weathering in agricultural soils to remove carbon dioxide

Abstract Silicate weathering moderates atmospheric CO2 levels over geologic time but proceeds naturally at rates too slow to substantially mitigate anthropogenic emissions. Microorganisms can accelerate silicate weathering and may thereby augment carbon dioxide removal. Here, we demonstrate that Bacillus subtilis strain MP1 can couple silicate dissolution with carbonate precipitation to capture CO2. In culture, MP1 formed biofilm in the presence of feldspar and increased silicate dissolution rates, pH and calcium carbonate formation relative to MP1-free controls. In a soil column experiment, MP1 enhanced inorganic carbon accumulation and the levels of available Ca2+, Mg2+, Fe2+, and Al3+. These results suggest that MP1 was able to accelerate the weathering of silicates naturally present in the soil to release cations. In field experiments, application of MP1 increased soil inorganic carbon and exchangeable calcium, resulting in a gross accrual of 2.02 tonnes inorganic C ha-1 y-1 in the uppermost 30 cm of the soil column. Our results are consistent with a 'trans' calcification type model in which MP1 links silicate dissolution with calcite precipitation via cross-biofilm Ca2+ and proton transport. Furthermore, our results demonstrate the potential for microbially-enhanced silicate weathering in agricultural soils to promote inorganic carbon accumulation and removal of atmospheric CO2.