Eight fundamental differences between CBAM and LCA

If you have an EPD in hand while preparing a CBAM report, you will be tempted to copy the GWP value across. Do not. The two calculations can draw on the same raw data but ask different questions and produce different numbers. Eight structural differences decide which number belongs where.

1. Purpose: tax base versus decision support

CBAM’s output is a liability calculation; the number’s only function is to determine how many certificates are surrendered. LCA’s output is a decision-support instrument, used to compare design options, find hotspots and prioritise improvement. That difference in purpose explains most of the methodological divergence.

2. System boundary

CBAM covers defined production processes up to the installation gate. Full upstream extraction, transport, packaging, the use stage and end-of-life are out of scope. An EN 15804+A2 EPD can extend beyond A1–A3 to A4–A5, the B modules, the C modules and Module D. For the same product, the CBAM number does not even map one-to-one onto the EPD’s A1–A3 total.

3. Gases covered

CBAM covers specific gases by sector: CO₂ in cement and steel, CO₂ and PFCs in aluminium, CO₂ and N₂O in fertilisers. In LCA the GWP indicator covers the full Kyoto basket, and EN 15804+A2 splits it three ways: fossil, biogenic and land use related. CBAM has no such split.

4. Treatment of biogenic carbon

EN 15804+A2 tracks biogenic carbon as a separate indicator and reports carbon bound in the product as a negative value. CBAM has no separate biogenic indicator; CO₂ from sustainable biomass fuel is generally counted as zero. In a cement plant running alternative fuels, that difference produces visibly different numbers in the two reports.

5. Allocation rules

In LCA, allocation is a methodological choice; ISO 14044 asks you to avoid it first, then use physical relationships, and only then economic value, justifying your choice. CBAM prescribes: production processes map to goods, and splitting uses defined keys. There is no latitude, so there is no justification either.

6. Recycling and Module D

EN 15804+A2 reports recovery benefits beyond the system boundary separately in Module D, a significant line for high-recycling materials such as steel and aluminium. CBAM has no such module — what happens at end-of-life does not enter the calculation. Using recycled input shows up only indirectly, through the low emissions of the secondary material.

7. Data source hierarchy

In LCA, foreground data is primary and background data comes from a database such as ecoinvent, which is considered normal practice. CBAM has no concept of a background database; there is either actual installation data or a default value. An emission factor taken from an ecoinvent activity is not a valid source in a CBAM declaration.

8. Verification regime

EPD verification is managed by a program operator under ISO 14025, and the verified EPD is published publicly. CBAM verification is carried out by a verifier from the ETS accreditation framework, and the result is not public; it stays between the importer and the customs authority. Neither verification substitutes for the other.