Carbonic anhydrase-mediated CO2 sequestration in cementitious materials: Challenges and opportunities

The cement industry accounts for up to 8% of global CO₂ emissions, with natural carbonation during the concrete life cycle offsetting only 16–30% of these emissions. Conventional accelerated carbonation is energy-intensive and limited to controlled pre-cast environments. Bio-based enzymatic approaches by adding carbonic anhydrase (CA) as a catalytic enhancement during carbonation offer a promising pathway for accelerating CO₂ sequestration by catalyzing the rate-limiting CO₂ hydration to bicarbonate (HCO₃⁻), facilitating subsequent CaCO₃ precipitation. However, CA’s effectiveness is controlled by cementitious material properties. CA rapidly loses activity at pH 13 (fresh concrete) while remaining functional at pH 10–12 (characteristic of recycled concrete materials). Therefore, this perspective review concludes that CA is ideally suited to end-of-life recycled concrete materials, particularly recycled concrete fines and powders (RCFs and RCPs), which offer high surface area-to-volume ratios and favorable pH conditions for efficient CA-mediated CO₂ capture. We discuss various strategies to enhance CA stability in cementitious systems, including enzyme immobilization, selection of robust CA variants, and protein engineering. While CA shows promising potential for recycled concrete materials, practical implementation of CA-mediated CO₂ sequestration requires strategic approaches to align material properties with CA functional requirements.