DEMONSTRATION OF ENHANCED CARBON MINERALIZATION WITHIN ULTRAMAFIC MINE TAILINGS

Enhanced mineralization is a recognized carbon dioxide (CO₂) removal pathway whereby atmospheric CO₂ is captured through chemical reactions during the weathering of alkaline wastes, such as mine tailings. CO₂ in air reacts with cations from alkaline mine tailings (Mg²⁺, Ca²⁺) to form carbonate minerals that are isolated from the atmosphere and stored over geological time scales. Mine tailings from ultramafic ore passively captures CO₂ after being deposited from a slurry at very slow rates, but the capture rates of CO₂ can be enhanced through the manipulation of the surface of the tailings storage facility.

Here we report on a hectare-scale demonstration of enhanced mineralization from the Arca Climate Technologies feasibility pilot of integrated Smart Churning technology with continuous monitoring of CO₂ capture. The tailings surface is roughened using physical manipulation techniques in a multi-hectare plot to increase the rate of CO₂ capture from air. CO₂ removal is directly measured at a point-scale using commercially available dynamic closed chambers, and at a larger-scale with eddy covariance monitoring. The two independent methods measure similar CO₂ removal rates. Results demonstrate that the rate of capture from Smart Churning is significantly increased over baseline passive air capture rates. Mineral trapping is confirmed with electron microscopy imaging of the carbonate mineral cements that bind milled tailings grains. This process has been formalized in a methodology that has been independently validated as ISO compliant (ISO14064-2:2019).