Cement is the sector where CBAM’s core assumption — that fuel combustion drives industrial emissions — breaks down, because most of cement’s carbon footprint comes from a chemical reaction, not a burner.

In this article:

• Which cement products and CN codes fall under CBAM
• Why calcination, not fuel, produces most of cement’s CO2
• The default numbers you need: the 0.525 clinker factor and typical clinker-to-cement ratios
• How clinker and calcined clay function as tracked “precursors”
• The bubble approach, sector exemptions, and how to actually lower your exposure

Quick refresher for anyone new to this series: CBAM makes imported goods pay a carbon cost comparable to what EU factories already pay under the EU Emissions Trading System. Importers of covered goods buy CBAM certificates tied to embedded emissions, with the definitive period — real financial obligations, not just reporting — underway from 2026. Full mechanics are in the first post in this series.

Cement is one of the six original CBAM sectors, and one of the more counterintuitive ones. Most people picture cement emissions as a fuel problem — a big kiln burning coal. That’s part of the story, but not the biggest part.

Which Cement Products Does CBAM Actually Cover?

CBAM’s cement scope is narrower than “cement” as a category. The EU guidance defines four aggregated goods categories, each tied to specific CN/TARIC codes:

In plain terms: CBAM covers clinker (the unfinished intermediate that becomes cement), calcined clay (a clinker substitute), the various Portland and hydraulic cements, and aluminous cement. One detail that trips people up: white and grey clinker or cement have different benchmarks and emission factors, so they must be tracked and reported as separate product lines, never blended into one average.

The Counterintuitive Part: Where Cement’s Carbon Actually Comes From

Here’s the fact non-technical readers usually get backwards. Cement is made by heating limestone and clay in a kiln to produce clinker, then grinding that clinker with gypsum and other materials into finished cement. It’s easy to assume the emissions all come from burning fuel to heat the kiln. They don’t.

The dominant source is calcination — a chemical reaction, not combustion. When limestone (calcium carbonate) is heated, it breaks down into calcium oxide and releases CO2 as a direct byproduct of that transformation. That CO2 would be released even on a zero-emission fuel, because it’s coming out of the rock itself, not the flame heating it.

Smaller process sources add on top of calcination: non-carbonate carbon in raw materials like carbonaceous clay or shale, alternative raw materials such as fly ash in the raw meal, partially calcined dust leaving the kiln, and carbonate-based reagents used to clean flue gas. All of these sum into one total direct-emissions figure for the installation, not separate line items.

Fuel combustion still matters — kiln and non-kiln, conventional fossil, alternatives like petroleum coke or waste tyres, and biomass or waste-derived fuels. But it’s a contributor alongside process emissions, not the main event.

The single most important, and most counterintuitive, fact about cement’s CBAM emissions: most of the CO2 comes from limestone breaking down, not from the fire underneath it.

Cement production flow, with the calcination step — cement’s dominant emission source — marked separately from fuel combustion and electricity.

Cement isn’t on CBAM’s “direct-emissions-only” list, which applies to a small number of sectors. That means indirect emissions — the CO2 tied to electricity a plant purchases — count toward the total too, reported separately from direct emissions but very much part of the final bill.

The Default Numbers You Need to Know

Two figures do most of the work in cement CBAM calculations.

0.525 tonnes of CO2 per tonne of clinker is the standard default process emission factor for clinker. It’s a regulatory floor — operators can measure their own raw meal in a lab and use a more accurate, lower figure, but 0.525 is the fallback used throughout the official worked examples and applies by default if better data isn’t supplied.

The clinker-to-cement ratio (CCR), or clinker factor, is the tonnes of clinker consumed per tonne of finished cement. Because clinker is where almost all the emissions live, CCR is the single biggest driver of a cement product’s carbon footprint. Ordinary Portland cement typically runs 80–95% clinker. Under the European EN 197-1 standard, blended or composite cements (CEM II through CEM V) can range down to 5–20% clinker content, substituting in slag, fly ash, or calcined clay.

That spread matters — two tonnes of “cement” under different formulations can carry wildly different embedded emissions, purely from how much clinker sits inside each one. Custom compositions must be calculated against actual clinker content, not a generic average, meaning per-consignment declarations become part of doing business.

One more default: mineral additives — gypsum, blast furnace slag, fly ash, natural pozzolana — are treated as having zero embedded emissions of their own, folded into the plant’s overall direct and indirect totals rather than tracked separately.

Lower clinker content generally means lower embedded emissions per tonne of cement — the main lever producers control.

Clinker and Calcined Clay as Precursors

CBAM treats clinker and calcined clay as the sector’s only two precursor materials — inputs that are themselves CBAM goods with their own embedded emissions, which then “travel with” the finished product.

Clinker and calcined clay are both “simple goods”: produced without any other CBAM good as an input, so their emissions are calculated from scratch. Finished cement (other than aluminous cement) is a “complex good” precisely because it’s built by grinding clinker — and sometimes calcined clay — with gypsum and other additives. So when a clinker producer sells clinker onward, standalone or embedded inside a bag of cement, its emissions must be disclosed to whoever buys it next.

Aluminous cement is a partial exception. It’s made via an integrated, continuous process from bauxite and limestone straight through to finished cement, with no further additives — so despite involving clinker, it’s classified as a “simple good” inside one system boundary. Alumina, the bauxite-derived raw material, is treated as an ordinary raw material rather than a tracked CBAM precursor.

The Bubble Approach — and Its Limit

Many cement plants are vertically integrated: the same site runs the kiln and grinding mill, and 100% of clinker produced feeds directly into that plant’s own cement. For that situation, CBAM allows the “bubble approach” — combining clinker production and cement grinding into one joint system boundary, so the plant doesn’t need to separately track clinker’s own emissions or split electricity between the two stages.

The catch: if any clinker from that kiln is also sold or exported separately — even a portion, even occasionally — the bubble approach is off the table entirely. The operator then has to calculate and disclose clinker’s standalone embedded emissions to whoever buys it as its own product.

Sector-Specific Exemptions Worth Knowing

A handful of carve-outs are specific to cement:

• Non-calcined kaolinic clay is excluded outright — only the calcined subheading is a CBAM good.
• Infrastructure and equipment emissions (building and maintaining the plant itself) are excluded from the monitoring boundary.
• Mobile plant and vehicle emissions don’t count as direct emissions; only stationary combustion does.
• Mineral additives (gypsum, slag, fly ash, natural pozzolana) carry zero separately-tracked embedded emissions, as noted above.
• Carbon capture (CCS/CCU), where actually used, should be reflected in an operator’s actual-emissions calculation — but it isn’t built into the 0.525 default, which assumes no capture.

A Worked Example, Simplified

The official guidance walks through a plant producing 1,255,000 tonnes of clinker a year. Using the 0.525 standard factor, process emissions from clinker alone come to roughly 659,000 tonnes of CO2 — before combustion emissions are even added, which bring total direct emissions to just over 1,037,000 tonnes. Process emissions outweigh combustion emissions here, illustrating the calcination point directly.

Scaled to an import: 100 tonnes of Portland cement at a 0.95 clinker ratio carries total embedded emissions of about 87.7 tonnes of CO2. After the free-allocation adjustment available in 2026 (the phase-in mechanism common to all CBAM sectors, explained in our intro post), the net obligation works out to roughly 26 CBAM certificates for that shipment.

A simplified illustration of how a 100-tonne cement import’s obligation is worked out, based on the official guidance’s worked example.

Practical Ways to Reduce Exposure

None of this is fixed. A few levers actually move the number:

• Lower your clinker-to-cement ratio. Shifting toward blended or composite cements — substituting slag, fly ash, or calcined clay for clinker — is the single most direct way to cut embedded emissions per tonne.
• Use alternative fuels in the kiln. Since combustion is still a real, if secondary, contributor, switching toward lower-carbon or waste-derived fuels reduces that portion of the total.
• Pursue carbon capture where feasible. CCS/CCU isn’t in the default factor, so an operator that actually captures CO2 can reflect that in its real emissions figure instead of the 0.525 default.
• Get actual data flowing, not defaults. These improvements only help a buyer’s CBAM bill if the data reaches them — verified, precursor-level, batch-specific. Better numbers than the default earn no credit unless they’re actually reported.

How Sprih Helps

If you’ve read this far, you’ve probably noticed the pattern: cement’s CBAM exposure isn’t really a chemistry problem for the importer, it’s a data problem. Getting to an accurate number means chasing down clinker-level emissions data from a supplier, knowing whether your clinker producer uses the bubble approach, and tracking white versus grey product lines separately — all before you can even get to the certificate math.

That’s the layer we built Sprih for. Our SustainSense platform indexes sustainability and emissions data across more than 120,000 companies and 400,000 reports, giving importers and their teams a faster way to find, verify, and organize the supplier-level data CBAM calculations depend on. We’re also building CBAM-specific tooling designed to help importers and their upstream suppliers calculate and manage embedded-emissions data directly, rather than defaulting to conservative fallback values that cost more than the real number would.

Our view is simple: CBAM compliance is a supply-chain data problem before it’s a compliance problem, and companies that treat it that way turn it into an advantage rather than a cost center. Sprih is an AI-native sustainability intelligence company helping enterprises turn climate and compliance data into competitive advantage.