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Chain of Custody Models Compared
Four custody models, all standardised, all legitimate — and they mean very different things about what is physically in the product a customer is holding.
Chain of custody models determine what a recycled or certified content claim physically means. Identity preserved and segregated guarantee the material is present; controlled blending guarantees a ratio; mass balance guarantees only that an equivalent quantity entered the system somewhere upstream.
What this gives you
The four chain-of-custody models compared, what each lets you claim, and which one a verifier will accept for the recycled-content figure you want to publish.
Key takeaways
- All four models are legitimate and standardised — the failure is publishing one as though it were another.
- Mass balance permits a claim on a product containing none of the certified material.
- The model chosen determines cost, and cost is usually why the weaker model was selected.
- A passport should record the model alongside the percentage, or the percentage is uninterpretable.
A recycled content figure looks like a physical fact about an object. It is usually an accounting statement about a system, and which of the two it is depends entirely on the chain of custody model behind it.
ISO 22095 standardises the models. Understanding them is the difference between publishing a defensible claim and publishing one that collapses the first time a journalist or a competitor asks how it was calculated.
The four models
They form a spectrum from physical certainty to accounting equivalence, with cost falling as certainty does.
| Model | Is the material in this product? | Cost to operate | Typical use |
|---|---|---|---|
| Identity preserved | Yes, and from one identified source | Highest | Single-origin provenance claims |
| Segregated | Yes, from certified sources, kept apart | High | Certified timber, organic fibres |
| Controlled blending | Partly, at a declared ratio | Moderate | Blended fibres, board products |
| Mass balance | Not necessarily | Lowest | Chemical recycling, bulk polymers |
The fourth row is the one that causes trouble. Under mass balance, a producer takes in a proportion of certified feedstock, mixes it with uncertified material in a process where separation is impractical, and allocates the certified claim to a corresponding proportion of output. The molecules in any given product may be entirely uncertified.
Why mass balance exists
It is easy to present mass balance as a loophole. It is more accurately a response to a genuine physical constraint, and dismissing it removes the only viable route for several material streams.
Chemical recycling of plastics feeds recovered material into a cracker alongside virgin feedstock. The outputs are molecularly identical and cannot be separated. Requiring segregation would mean building a parallel plant, which for most polymers is not economic and would simply stop the recycled material entering the system at all.
What goes wrong in practice
The recurring failure is not choosing mass balance. It is choosing mass balance for cost reasons and then describing the result in the vocabulary of segregation.
- "Made with 30 % recycled content" applied to a mass balance allocation. The phrasing asserts physical presence the model does not support.
- A percentage with no model stated, which a downstream customer will assume is segregated because that is the intuitive reading.
- Aggregating models — averaging a segregated figure from one supplier with a mass balance figure from another produces a number describing nothing.
- Losing the model in transmission, where the supplier declared it correctly and it was dropped when the value was copied into a product master.
The last of these is the most common and the most preventable. The model is usually stated on the certificate and then discarded at the first system boundary because the receiving field only accepts a number.
How to record it in a passport
The requirement is simple to state and requires a data model that anticipates it: the percentage and the model travel together as one value, and the certificate reference travels with both.
The scheme and certificate the claim rests on.
Different targets are written against each.
Identity preserved, segregated, blended or mass balance.
Meaningless on its own, and the only part usually published.
A product master with a single numeric field for recycled content cannot represent this, which is why the fix is usually a schema change rather than a policy one.
What auditors actually check
Scheme audits of a mass balance operation concentrate on the accounting rather than the product, which surprises companies expecting a materials inspection.
The questions are whether certified input actually entered the system in the quantity claimed, whether the conversion factor applied to that input is justified by process yield, and whether output allocations sum to no more than the input allows. Over-allocation is the failure that ends certifications, and it usually arises from an optimistic yield assumption rather than deliberate inflation.
For a downstream buyer, that means the useful question to a supplier is not whether they hold a certificate but what conversion factor they apply and who verified it.
Choosing a model deliberately
The right approach is to decide what claim you want to make, then select the cheapest model that supports it, rather than selecting on cost and describing whatever results.
If the claim is about this specific product containing this specific material, segregation or identity preservation is required and should be budgeted. If the claim is about supporting recycled material entering the economy, mass balance is appropriate, cheaper, and entirely defensible provided the language matches.
The commercial risk sits almost entirely in the mismatch. A mass balance claim described accurately attracts no criticism; the same claim described as physical content is the one that becomes a case study in greenwashing enforcement.
Frequently asked questions
What is mass balance in simple terms?
A bookkeeping approach in which certified and uncertified material are mixed in a process where separation is impractical, and the certified claim is allocated to a corresponding proportion of output. The specific product carrying the claim may contain none of the certified material.
Is mass balance greenwashing?
Not inherently. It is a standardised model that allows recycled material to enter processes where segregation is physically impractical, such as chemical recycling. It becomes misleading when a mass balance allocation is described in language implying the material is physically present in the product.
Which model should we use?
Decide the claim first, then choose the cheapest model that supports it. A claim about this product containing this material requires segregation or identity preservation. A claim about supporting recycled material entering the economy is properly served by mass balance at considerably lower cost.
Can we average recycled content across suppliers?
Only within the same model. Averaging a segregated figure from one supplier with a mass balance figure from another produces a number that describes nothing and cannot be defended. Where models differ, the components have to be reported separately rather than combined.
How do we record this in a product passport?
As a composite value: the percentage, the chain of custody model, whether the content is pre- or post-consumer, and the certificate reference. A single numeric field cannot represent the claim, which is why this usually requires a schema change rather than a policy decision.
What standard governs chain of custody?
ISO 22095 defines the models and their requirements, and individual certification schemes implement them with sector-specific rules. Referring to the scheme alone is insufficient, because most schemes permit more than one model and the choice materially changes what the claim means.
Does the model affect producer responsibility fees?
It can, where a scheme’s eco-modulation rewards recycled content and specifies which models qualify. Some schemes accept mass balance and others require physical presence, so the model chosen for a material can change the fee outcome in one market while making no difference in another.
Sources
- Regulation (EU) 2024/1781 establishing a framework for ecodesign requirements — EUR-Lex, European Union, 2024-06
- Directive 2008/98/EC on waste (Waste Framework Directive) — EUR-Lex, European Union, 2008-11
Continue reading
- Getting data out of deep-tier suppliersHow custody evidence is obtained from the tiers that actually hold it.
- Getting fibre composition data rightA worked example where the custody model changes what the number means.
- Verifiable Credentials explainedHow a custody certificate becomes a claim software can check.
- Supply chain traceabilityCustody transfers recorded as events against the product record.