Ambient Weathering of Magnesium Oxide for CO Removal from Air

To avoid dangerous climate change, new technologies must remove billions of tonnes of CO from the atmosphere every year by mid-century. Here we detail a land-based enhanced weathering cycle utilizing magnesite (MgCO) feedstock to repeatedly capture CO from the atmosphere. In this process, MgCO is calcined, producing caustic magnesia (MgO) and high-purity CO. This MgO is spread over land to carbonate for a year by reacting with atmospheric CO. The carbonate minerals are then recollected and re-calcined. The reproduced MgO is spread over land to carbonate again. We show this process could cost approximately $46-159 tCO net removed from the atmosphere, considering grid and solar electricity without post-processing costs. This technology may achieve lower costs than projections for more extensively engineered Direct Air Capture methods. It has the scalable potential to remove at least 2-3 GtCO year, and may make a meaningful contribution to mitigating climate change.