Engineered bacterial siderophore production accelerates rock weathering for carbon removal

Silicate mineral weathering (dissolution) is a scalable strategy for capture and storage of CO2 but is too slow for industrial deployment. Bacteria can accelerate mineral dissolution by secreting siderophores, molecules that solubilize iron released from the mineral. Here we investigate how to deploy siderophore-producing bacteria at scale to continuously enhance dissolution of the mineral olivine. We demonstrate that natural genetic regulation precludes continuous siderophore production in mineral bioreactors. To overcome this limitation, we engineer the marine bacterium Alteromonas macleodii for enhanced siderophore production, conferring a 2.6-fold increase in the rate of olivine dissolution. Life-cycle analysis indicated that renewable feedstocks and minimal replenishment of modified cells are critical to achieve net CO2 removal at scale. With these guidelines, we constructed pilot-scale continuous mineral bioreactors that use unprocessed seawater and a renewable acetate feedstock to weather 4 kg of olivine. In reactors with engineered cells, we directly measured removal of 0.50 g CO2 per day from the air through alkalinity generation. Engineered bacteria speed up rock weathering for carbon capture in a seawater bioreactor.