Wood contains the amount of carbon that wood contains: what 40 timber EPDs revealed about biogenic carbon reporting
Biogenic carbon should be one of the easiest things to get right in a timber EPD. The product is made of wood. Wood has a known carbon content. The declared biogenic carbon should match the amount of biological material that physically exists in the product.
So I tested that assumption.
The setup
I took 40 timber product EPDs. All EN 15804+A2. All published in 2025. All from three major programme operators.
Then I manually checked how biogenic carbon was reported in every single one. For each EPD, I cross-checked the declared kg C against the material composition and the bio-based shares — in both the product and the packaging.
This is not an exotic check. It requires no special interpretation of the standard. EN 15804+A2 requires biogenic carbon content to be declared for the product and for the packaging, and that declaration has a physical anchor: the biological material actually in the product. Standards can sometimes be interpreted creatively, but wood still contains the amount of carbon that wood contains.
What I found
Some EPDs were fine. The declared biogenic carbon matched what the material composition said should be there.
Some were… aspirational. Declared carbon that the stated composition could not physically account for. Mismatches between the bio-based share and the declared kg C. Packaging biogenic carbon that didn’t line up with the packaging described.
In total, 11 of the 40 EPDs had issues. That’s more than a quarter — in published, third-party verified documents, on a check that comes down to basic mass balance.
This matters beyond tidiness. Biogenic carbon figures flow into building-level LCA calculations, procurement comparisons, and increasingly into regulatory reporting. When the declared carbon doesn’t match the physical product, everyone downstream inherits the error — usually without knowing it.
Then I ran the same 40 through Lodestellar
This was the part I actually wanted to test. Manual review works, but it doesn’t scale, and the whole point of building automated EPD quality checks is that they should hold up against an expert doing the same work by hand.
Lodestellar caught the exact same problematic EPDs I did. Every single one. No misses. No false alarms.
That’s the result that matters. Not because biogenic carbon is the hardest check in an EPD — it isn’t. But precisely because it’s easy to get wrong and easy to verify, it’s a clean benchmark: if a tool can match a manual expert review on a check like this, across 40 real published documents from three programme operators, the tool is doing something useful.
What this means if you work with EPDs
If you develop EPDs: this is the kind of issue that is cheap to fix before submission and expensive to fix after. A biogenic carbon mismatch found during verification means back-and-forth, delays, and rework. Found after publication, it means a correction — or a published document that doesn’t hold up to scrutiny.
If you verify EPDs: 11 in 40 slipped through somewhere. Verifiers are working under real time pressure, and a systematic pre-check on the mechanical, physically-anchored parts of an EPD frees attention for the judgment calls that actually need a human.
If you use EPDs: published and verified does not automatically mean the numbers reconcile. It’s worth knowing which documents you can lean on.
The practical takeaway
If you’re creating, checking, or verifying EPDs, run them through Lodestellar before publication. A review costs €7 and takes about an hour.
Worst case: everything checks out and you’ve spent 7 euros confirming it. Best case: you catch something before it becomes a case study.
Eleven of forty had issues. This is probably worth checking before publication.
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