Global decarbonization potential of CO₂ mineralization in concrete materials

CO₂ mineralization products are often heralded as having outstanding potentials to reduce CO₂-eq. emissions. However, these claims are generally undermined by incomplete consideration of the life cycle climate change impacts, material properties, supply and demand constraints, and economic viability of CO₂ mineralization products. We investigate these factors in detail for ten concrete-related CO₂ mineralization products to quantify their individual and global CO₂-eq. emissions reduction potentials. Our results show that in 2020, 3.9 Gt of carbonatable solid materials were generated globally, with the dominant material being end-of-life cement paste in concrete and mortar (1.4 Gt y^-1). All ten of the CO₂ mineralization technologies investigated here reduce life cycle CO₂-eq. emissions when used to substitute comparable conventional products. In 2020, the global CO₂-eq. emissions reduction potential of economically competitive CO₂ mineralization technologies was 0.39 Gt CO₂-eq., i.e., 15% of that from cement production. This level of CO₂-eq. emissions reduction is limited by the supply of end-of-life cement paste. The results also show that it is 2 to 5 times cheaper to reduce CO₂-eq. emissions by producing cement from carbonated end-of-life cement paste than carbon capture and storage (CCS), demonstrating its superior decarbonization potential. On the other hand, it is currently much more expensive to reduce CO₂-eq. emissions using some CO₂ mineralization technologies, like carbonated normal weight aggregate production, than CCS. Technologies and policies that increase recovery of end-of-life cement paste from aged infrastructure are key to unlocking the potential of CO₂ mineralization in reducing the CO₂-eq. footprint of concrete materials.