Carbon Dioxide Removal by Construction Waste: Experimental Assessment of CO2 Capture Efficiency

As one of the world largest waste streams, cement-based construction materials offer a potentially scalable pathway for CO₂ removal (CDR) through aqueous mineral carbonation, yet their efficiency and practical constraints remain poorly characterized. Here, we conducted controlled experiments to quantify CO₂ capture by cement-based materials in aqueous conditions, tracking changes in headspace CO₂, aqueous compositions, and CaCO₃ formation. Headspace CO₂ declined rapidly during carbonation, with the conversion to CaCO₃ reaching up to 70% of the solid material within days. Reaction process was influenced by particle size, with finer materials sustaining CO₂ uptake over longer periods due to higher reactive surface area. Based on the observed CO₂ capture efficiency, applying carbonation to construction-waste streams globally could potentially sequester CO₂ at the million tonnes scale annually. These findings demonstrate the practical potential of aqueous CO₂ capture by construction waste, and highlight opportunities to integrate this pathway into managed environmental systems, such as water and agricultural infrastructures, within broader CDR application.