A new perspective published in Engineering reveals critical limitations in using cement carbonation as a core climate mitigation strategy, challenging widely adopted accounting practices for the cement industry, which contributes 5%–8% of global anthropogenic CO₂ emissions. Carbonation, the natural process where concrete reabsorbs atmospheric CO₂ over decades, has been proposed to offset roughly 50% of process emissions, yet systematic analysis shows this benefit is overstated due to time delays, performance uncertainty, and methodological weaknesses in current climate accounting frameworks.

The research highlights severe temporal asymmetry between cement production and carbonation: intense CO₂ pulses occur during manufacturing, while absorption proceeds slowly via diffusion-limited reactions spanning decades. When evaluated with time-adjusted climate metrics, the purported climate benefits drop by 30%–60% relative to conventional global warming potential calculations that ignore timing differences. A synthesis of 99 published carbon capture and utilization concrete scenarios further shows that 52% have less than 50% probability of achieving net emission reductions; many suffer from reduced compressive strength, requiring extra binder that erodes carbon gains.

The study identifies three systemic failures in current accounting: treating delayed absorption as equivalent to immediate emission cuts, selective reporting that hides underperforming cases, and policy support for slow, uncertain pathways while proven alternatives are underused. Unlike carbonation, supplementary cementitious materials deliver 11%–34% emission cuts via direct clinker substitution; structural design optimization achieves 18.5% reductions without sacrificing safety; and service life extension could enable up to 75% total emission reduction potential by 2100, all offering immediate, verifiable benefits.

These findings call for revised climate governance for cement, emphasizing time-explicit accounting with discounting for delayed carbonation uptake, strict verification for carbonation-related projects, and policy prioritization of established, low-uncertainty decarbonization levers over long-term, unreliable sequestration pathways. The authors note that while carbonation is chemically feasible, its slow kinetics and uncertain performance make it unsuitable as a primary near-term decarbonization solution, urging a shift toward evidence-based strategies aligned with urgent climate targets.

The paper “The Carbonation Trap: Time Delays and Performance Uncertainty in Cement Climate Accounting,” is authored by Haoxuan Yu, Jilong Pan, Izni Zahidi, Chow Ming Fai, Dongfang Liang. Full text of the open access paper: https://doi.org/10.1016/j.eng.2025.11.006. For more information about Engineering, visit the website at https://www.sciencedirect.com/journal/engineering.