Energy pathways for cement decarbonisation within global mitigation pathways through life-cycle scenario analysis

Cement manufacture is a cornerstone of the built environment and a major source of industrial greenhouse-gas emissions. This study assesses how alternative energy mixes and clinker-replacement strategies can align a representative cement production system with the safe and just Earth-system boundaries framing and the mitigation pathways assessed by the IPCC. A cradle-to-gate life-cycle assessment was conducted using publicly available inventory data for seven energy scenarios (fossil baseline, natural gas, solid-recovered fuel, sustainable biomass within resource limits, electrified kiln, green hydrogen, and hybrid combinations) and three levels of clinker substitution by supplementary materials. Sector-scale abatement was expressed via a Pathway Alignment Index estimating the share of the global mitigation gap each scenario could close in 2030 and 2050 relative to IPCC pathway bands. Results indicate that moderate fuel switching and partial clinker substitution move the sector toward intermediate (≈4.5~W/m2) trajectories, whereas electrification and hydrogen pathways approach stringent (≈2.5 W/m2) trajectories when supported by low-carbon power. Process emissions from limestone calcination remain a residual source, suggesting that carbon-capture options represent an enabling complement rather than the main lever. Bioenergy contributions are bounded by land, water and biodiversity constraints highlighted in recent planetary-boundary analyses. The findings suggest that timely decarbonisation depends primarily on clean-energy access and material innovation while remaining within Earth-system limits.