CO2-Free Cement
About 60% of cement emissions come from the limestone itself; an affordable, approved alternative at million-tonne scale is missing.
Open in the interactive tree →Cement causes about 8% of global CO2 emissions; when limestone is burned (CaCO3 becomes CaO + CO2) roughly half a tonne of CO2 per tonne of clinker escapes from the chemistry, on top of kiln heating. Renewable power alone does not fix that. Routes are capture, low-limestone binders, electrochemical processes and less clinker per cubic metre of concrete.
As of October 2026
Brevik (Norway) has captured CO2 since 2025 - designed for about half of the plant's emissions - and shows that CCS works technically in a cement plant. The much larger Edmonton plant (Canada, 1 Mt CO2 per year) was put on hold in August 2026 with no new date, because Canadian carbon prices of about US$32 per tonne did not justify the cost. Electrochemical newcomers such as Sublime Systems have so far delivered pilot quantities (for example for a data-centre project in Virginia in 2025). No process yet makes cement without process CO2 at million-tonne volumes at competitive prices.
What is missing
- Binders without limestone process CO2 that standards and building codes accept (approvals take years)
- Affordable CCS at the cement plant including CO2 transport and storage
- Enough cement substitutes - slag and fly ash get scarcer with the coal phase-out
- Willingness to pay: green cement costs noticeably more, builders and lawmakers must go along
- Scaling pilot plants to millions of tonnes per year
Becomes possible once solved
- Climate-neutral buildings and infrastructure
- City growth in Asia and Africa without an emissions surge
- Concrete as a CO2 sink when carbonation is used deliberately
Open steps
- Binders without limestone CO2 Medium AI leverageFind cheap binders (calcined clays, belite, electrochemical or magnesium-based) that match cement strength and durability without calcining limestone.
- Mix designs with less clinker High AI leverageOptimize blends of clinker, slag, fly ash, calcined clay and fillers for strength, curing speed and carbon footprint.
- Predicting long-term durability Medium AI leveragePredict 50-year durability (carbonation, chloride, sulfate attack) from short tests so standards bodies can approve new binders sooner.
- Capture integrated with the kiln Medium AI leverageIntegrate CO2 capture into kilns using less heat and solvent, and lower the cost per captured tonne.
- Supply of cement substitutes Medium AI leverageFind and qualify alternatives to slag and fly ash, such as natural pozzolans, calcined clays and recycled concrete fines, region by region.
Where AI could help
Medium AI leverage. AI speeds mix design and binder search; cost, building-code approval and CO2 transport and storage decide whether low-carbon cement spreads.
- Optimize cement-replacement mixes (slag, fly ash, clays) for strength, curing speed and carbon
- Screen new low-CO2 binder chemistries with machine-learned simulations
- Optimize kiln and capture-plant operation to cut fuel use
Shown so far
- In July 2025 Meta reported an AI-optimized low-carbon concrete mix (Bayesian optimization) poured in a data-center slab section in Minnesota; it needed minor human adjustments and further testing. source
Prerequisites
- Portland Cement1824CO2-free cement replaces the Portland cement chemistry
- Thermodynamics1824
- Concrete & Reinforced Concrete1867
- Cement with CO2 Capture2025