Cement production becomes more sustainable when it cuts both the amount of clinker and energy needed for each tonne, uses lower-emissions fuels, improves material efficiency, and captures residual process and combustion carbon dioxide. Progress must be measured with more than one number: total tonnes of emissions, emissions per tonne of product, clinker content, kiln energy, fuel mix, captured carbon and product-level life-cycle reporting all describe different parts of the result.
The distinction between absolute emissions and emissions intensity is essential. A plant can reduce CO2 per tonne while total emissions rise if output grows. Conversely, total emissions can fall simply because production declined. The International Energy Agency (IEA) reports that cement-sector total CO2 emissions remain above 2015 levels while direct emissions intensity has been unchanged in recent years, showing why both measures are needed.
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What sustainability means in cement production
Cement has two unusually difficult sources of climate emissions. Heating limestone in the kiln releases process CO2 as the mineral decomposes, and the kiln requires very high temperatures that normally come from fuel combustion. Efficiency and renewable electricity can reduce some energy impacts, but they do not remove the calcination reaction itself. A credible sustainability claim therefore identifies the intervention, the product being measured and the emissions boundary.
Climate performance is only one part of sustainability. Local air pollutants, water use, quarry land, biodiversity, worker safety and community impacts need separate indicators and evidence. A low-carbon figure should not be presented as proof that every environmental or social impact is low.
Production changes that reduce emissions
Use less clinker in each tonne of cement
Clinker is the kiln-made intermediate that supplies cement with its binding properties. Replacing a suitable share with supplementary cementitious materials (SCMs)—including slag, fly ash, calcined clay or natural pozzolans—can avoid some calcination and kiln energy per tonne of cement. The feasible percentage depends on local SCM availability, cement standards and the strength, durability and setting performance required by the application.
This is not a license to maximize substitution regardless of performance. A lower clinker ratio is useful only when the resulting cement meets the specification for its intended concrete or construction use. Report the cement type and clinker-to-cement ratio, rather than describing an unspecified “blended” product.
Improve kiln thermal efficiency
Process controls, heat recovery, equipment upgrades and stable kiln operation can reduce the gigajoules of thermal energy needed for each tonne of clinker. Thermal efficiency primarily addresses combustion energy; it does not eliminate the CO2 released by calcination. Comparisons should state which kiln operations and fuels are included, because plant boundaries differ.
Change the fuel mix carefully
Replacing higher-emissions fuels with lower-emissions alternatives can cut combustion emissions. The accounting must identify the fuel’s origin and distinguish biogenic from non-biogenic portions of waste-derived fuels. A claim based on a “renewable” or “alternative” fuel is incomplete unless it explains how its emissions were counted and what share of thermal energy it supplied.
Use cement and concrete more efficiently
Designers can avoid unnecessary cement through structural optimization, appropriate strength specifications, longer service life and efficient use of materials. This is a demand-side measure: it reduces the amount of cement needed for a required function rather than changing the emissions intensity of a particular tonne. The IEA includes material efficiency as part of the sector’s transition.
Capture process and combustion CO2
Carbon capture and storage or use can address emissions that remain after efficiency, clinker substitution and fuel switching. Capture performance should be reported as tonnes captured, the capture boundary, transport and storage or use arrangements, and whether any downstream emissions or permanence assumptions are included. “Capture-ready” equipment is not the same as measured tonnes captured and permanently stored.
The measurement dashboard
No single headline metric can show whether cement production is becoming more sustainable. Use a dashboard in which every value has a product basis, time period, geography and emissions boundary.
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| Indicator | What it measures | What to specify |
|---|---|---|
| Absolute emissions | Total tonnes of CO2 (or CO2-equivalent) released over a period | Reporting year, plant or portfolio boundary, gases included and cement output for the same period |
| Emissions intensity | CO2 or CO2e per tonne of cement (or another declared product unit) | Whether it covers direct process and fuel emissions or a broader life-cycle boundary; product type and allocation rules |
| Clinker-to-cement ratio | Tonnes of clinker divided by tonnes of cement | Cement type, SCMs used and the period or batch represented |
| Kiln thermal energy intensity | Gigajoules of thermal energy per tonne of clinker | Included kiln operations, fuel boundary and whether the number is a site result or an average |
| Fuel mix | Share of thermal energy supplied by lower-emissions or alternative fuels | Energy basis, fuel origin and treatment of biogenic and non-biogenic fractions |
| Carbon capture | CO2 captured and its storage or use pathway | Tonnes captured, capture point, transport, storage/use and any crediting rules |
| Product EPD | Life-cycle impacts for a defined cement product | Declared or functional unit, life-cycle modules, product category rules (PCR), validity and verification status |
Always show absolute emissions alongside output. Intensity can improve while the sector’s total climate impact worsens when production expands. The IEA’s 2025 Breakthrough Agenda assessment says both total emissions and intensity need to decline for alignment with net-zero goals.
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IEA pathway figures: useful benchmarks, not plant guarantees
The IEA’s Net Zero Emissions Guide for cement, published 26 September 2023, gives illustrative pathway milestones. They are scenario values, not achieved global averages, regulatory limits or universal plant standards.
| Indicator | 2022 pathway value | 2030 pathway value | How to read it |
|---|---|---|---|
| Clinker-to-cement ratio | 0.71 | 0.65 | Lower means less clinker per tonne of cement, subject to product performance and material availability |
| Kiln thermal energy intensity | 3.6 GJ per tonne of clinker | 3.4 GJ per tonne of clinker | Lower energy demand per tonne of clinker; compare only with consistent plant boundaries |
| Low-emissions fuels’ share of thermal energy | 5% | 30% | Share of kiln thermal energy, not a percentage of cement or total plant energy |
Use the year and the words “IEA scenario” whenever quoting these figures. A plant above or below one milestone is not automatically sustainable; its product mix, local conditions, absolute output and other impacts still matter.
How to compare two cement emissions claims fairly
Numbers that look comparable often are not. Before ranking products or plants, check each item below.
Do these 3 things before closing this tab:
1Fix the driver behind crashes, sound loss and screen glitches2Clear out junk files and repair common Windows errors3Scan for outdated or missing drivers - takes under a minute- Product basis: Is the denominator a tonne of cement, a tonne of clinker, a cubic metre of concrete or a functional unit delivering a specified service?
- Boundary: Does the result cover direct kiln process and fuel emissions only, or a life-cycle assessment including raw materials, electricity, transport, use and end-of-life?
- Clinker ratio and cement type: Portland, portland-limestone, blended and masonry cements can have different compositions and performance requirements.
- Geography and period: Record the plant location, production route, reporting year and whether the value is site-specific, a national average or a modeled estimate.
- Accounting treatment: Check how SCMs, co-products, waste fuels, biogenic carbon, avoided burdens, offsets and captured CO2 were handled.
- Data quality: Prefer measured, auditable site data over undisclosed averages and assumptions. Confirm whether a third party verified the result.
The IEA’s definitions and measurement methodology work calls for interoperable, net-zero-compatible reporting with comparable boundaries, coherent results, auditable measured data and consistent chain-of-custody rules. It also describes an ISO and GHG Protocol partnership intended to harmonise standards and develop emissions measurement and reporting standards. Until those approaches are consistently applied, a lower number may reflect accounting choices rather than a lower physical impact.
Understanding “near-zero” cement thresholds
The IEA’s proposed near-zero threshold ranges from 125 to 40 kg CO2e per tonne of cement, depending on clinker ratio. The range is conditional: it is not one blanket pass/fail number for every cement product. A cement with a different clinker ratio has a different threshold under the proposal.
That threshold addresses greenhouse-gas performance under a defined methodology; it is not a complete definition of sustainability. It does not, by itself, establish acceptable water use, quarry impacts, local air quality, worker conditions or biodiversity outcomes. Read the full boundary and product rules before using the threshold in procurement or policy.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Environmental product declarations and changing reporting rules
An environmental product declaration (EPD) presents life-cycle impacts for a specific product under stated product category rules. EPDs can make procurement more informed, but two declarations are comparable only when their PCR, declared or functional unit, life-cycle modules, allocation rules, geography, data period and verification arrangements align. The IEA identifies EPDs as an existing emissions reporting and labelling tool.
On October 5, 2026, the American Cement Association announced a partnership with the Slag Cement Association, Natural Pozzolan Association and American Coal Ash Association on SMART EPD® Part B Product Category Rules for Cementitious Materials, Standard 1000-017, version 1. The announcement says the consolidated PCR combines earlier rules for cement, slag cement and SCMs, with updated national-average EPDs planned for portland cement, portland-limestone cement, blended cements and masonry cement. This is a reporting-rule consolidation; it does not automatically make every existing or future EPD directly comparable.
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Jamie Farny, ACA Director of Environmental Measurement and Metrics, said: “The PCR consolidation was not only welcomed, but even requested, by several SCM producers and the groups that represent them.” The announcement is available from the American Cement Association. Treat national-average EPDs as averages, not measurements of every individual plant.
A practical workflow for evaluating a sustainability claim
- Define the decision. Write down whether you are selecting a cement product, evaluating a plant, setting a project target or tracking a corporate portfolio.
- Set the unit and boundary. Choose cement or clinker as the product basis and decide whether direct emissions or a full life-cycle result is required. Record the declared or functional unit.
- Request the underlying data. Ask for output, absolute emissions, emissions intensity, clinker ratio, kiln thermal energy, fuel shares and capture data for the same period.
- Check performance requirements. Verify that SCM substitution and the cement type meet the applicable specification for strength, durability, setting and exposure conditions.
- Review accounting rules. Examine PCR or LCA methodology, allocation of co-products, treatment of biogenic carbon, waste fuels, credits and captured CO2.
- Check verification and traceability. Prefer auditable site measurements or verified EPDs and document chain of custody for SCMs, fuels and captured carbon.
- Track totals and intensity over time. Plot tonnes of emissions and tonnes of product together. Investigate any divergence instead of relying on one favorable ratio.
- Report non-climate impacts separately. Add appropriate data for air pollutants, water, land, biodiversity, safety and community effects rather than hiding them behind a CO2 figure.
Common mistakes and how to avoid them
Calling a lower intensity “net zero”
A reduction in kilograms of CO2 per tonne is not net zero. Net-zero language requires a defined threshold, boundary, residual-emissions treatment and evidence for any storage or removals. Use “lower emissions intensity” when that is all the data demonstrate.
Comparing cement with clinker figures
Clinker is an input to cement, so the denominators are different. A kiln-energy result in GJ per tonne of clinker cannot be compared directly with a product EPD in kg CO2e per tonne of cement without reconciling the product basis and clinker ratio.
Ignoring growth in production
Efficiency projects can reduce emissions per tonne while total emissions increase. Publish annual output and absolute tonnes next to intensity so readers can see whether the change is operational, structural or simply due to volume.
Treating all SCMs and fuels as interchangeable
SCMs differ in availability and technical performance, while fuels differ in origin and biogenic content. State the actual material and accounting treatment instead of using a generic “alternative materials” or “renewable fuel” label.
Assuming one EPD proves every impact is low
An EPD reports the indicators and life-cycle modules required by its PCR. It does not replace site evidence for local pollution, water, land, safety or biodiversity, and it should not be compared across incompatible PCRs or units.
What a credible public claim should contain
A useful claim names the product, location, reporting period, emissions boundary, denominator, clinker ratio, energy and fuel data, capture treatment and verification status. It links to the applicable methodology or EPD and states whether values are measured at the site or represent an average. This level of detail lets a contractor, designer or buyer distinguish a real process improvement from a favorable but incomplete comparison.
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