Ambient weathering of magnesium oxide for CO₂ removal from air

To avoid dangerous climate change, new technologies must remove billions of tonnes of CO₂ from the atmosphere every year by mid-century. Here we detail a land-based enhanced weathering cycle utilizing magnesite (MgCO₃) feedstock to repeatedly capture CO₂ from the atmosphere. In this process, MgCO₃ is calcined, producing caustic magnesia (MgO) and high-purity CO₂. This MgO is spread over land to carbonate for a year by reacting with atmospheric CO₂. 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 tCO₂^-1 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 GtCO₂ year^-1, and may make a meaningful contribution to mitigating climate change.