CBAM and Cement: The Clinker Factor, Process Emissions and the Highest Cost-to-Value Ratio

Where cement emissions come from

Clinker production has two emission sources, and the distinction between them shapes the entire CBAM strategy for the sector.

Process emissions arise from the decomposition of limestone in the kiln. Calcium carbonate breaks down into calcium oxide and carbon dioxide, and the released CO₂ is an unavoidable product of the reaction. Roughly two thirds of clinker's emissions come from this source, and it does not change whatever fuel is used.

Combustion emissions come from the fuels burned to heat the kiln. Alternative fuels, waste heat recovery and kiln efficiency all reduce this component.

The consequence is that reducing emissions intensity in cement does not run through fuel conversion. Fuel improvements affect about a third of the total; the real lever lies elsewhere.

Clinker is the functional unit

In CBAM the carrier of the cement calculation is clinker. Cement's embedded emissions are built on the quantity of clinker it contains, which makes the clinker factor — the proportion of clinker in the cement — the strongest available lever.

Substituting clinker with slag, fly ash, calcined clay, pozzolans or limestone reduces embedded emissions directly and roughly proportionally. Lowering a clinker factor from 90% to 70% produces a reduction of broadly similar magnitude.

Two qualifications apply. Substitute materials can carry their own emissions load — calcined clay brings its own calcination emissions. And clinker and cement sit under separate CN codes, so calculations are built separately: there is no substitution lever available when clinker itself is the exported good.

Indirect emissions count here

Cement is one of the three product groups where CBAM counts indirect emissions, alongside fertilisers and agglomerated iron ore. The emissions of purchased electricity are added to the embedded figure.

Electricity consumption in cement concentrates in grinding. Its share of total emissions is modest next to calcination, but as the clinker factor falls the volume of ground substitute material rises and the weight of indirect emissions increases. Clinker substitution therefore lowers direct emissions while raising indirect ones somewhat; the net gain remains clear, but both sides of the calculation need to be built together.

Using actual values for indirect emissions requires a direct technical connection, a power purchase agreement, or accepted renewable certificates — guarantees of origin do not qualify. The rules are in CBAM indirect emissions and electricity.

Why cost-to-value is highest in cement

CBAM cost is calculated in euro per tonne. What determines its commercial significance is that figure as a proportion of the product's unit price.

Cement has the lowest value per tonne of any good in CBAM scope while carrying high emissions intensity. The combination puts the ratio of CBAM cost to product value at the top of the mechanism. The same absolute cost that is marginal for a high-value steel product bears directly on price competitiveness in cement.

The 2026 free allocation factor of 97.5% keeps that pressure contained for now. As the factor falls to 51.5% in 2030, however, the cost facing producers whose intensity exceeds the benchmark can reach a magnitude that outweighs the freight advantage of seaborne trade. We set out the projections in CBAM cost modelling 2026-2034.

Scope and precursor structure

The core of scope is CN 2523: cement clinker, white Portland cement, other Portland cements, aluminous cement and other hydraulic cements. Calcined kaolinic clays are also listed.

The precursor structure is comparatively simple: clinker is the covered precursor of cement. For grinding plants buying clinker, the supplier's data determines most of the figure; for integrated plants producing their own clinker, the calculation closes inside the installation. Integration is therefore an advantage in CBAM data management.

Preparation priorities

1. Separate calculations for clinker and cement. They sit under different codes; the export mix determines which is the priority.
2. Track the clinker factor per product. Reportable by recipe and by period, and reconcilable against production records.
3. Evidence limestone composition through analysis. Process emission calculations rest on raw material composition; sampling frequency and method must be documented.
4. Monitor the alternative fuel mix. Separating biomass content directly affects the combustion emission figure.
5. Split electricity consumption by process. Required because indirect emissions are in scope.

Frequently asked questions

How much does alternative fuel use reduce embedded emissions?

It affects combustion emissions only — roughly a third of the total. The effect increases where biomass content can be separately evidenced.

Does carbon capture feed into the calculation?

Captured and permanently stored CO₂ can be taken into account, but the documentation and verification requirements are demanding.

We export clinker. Can we still use the clinker factor lever?

No. Where clinker itself is exported there is no substitution lever; abatement is limited to combustion emissions and process efficiency.

Do default values make sense in cement?

Not for installations below the country average. Where the clinker factor is low, actual data is the only way to make that difference visible.

Sources

• European Commission — CBAM legislation and Annexes
• European Commission — CBAM definitive regime

We work on building product-level emissions calculations for clinker and cement and preparing them for verification, under our CBAM accounting and reporting service. You can contact us with your questions.