Recyclate procurement: specification is part of the supply strategy

The most useful specification change is to describe what the material must do in the buyer's process, rather than only what it is.

A buyer's process has a window: a range of material characteristics within which it runs reliably and produces acceptable output. Melt flow, for instance, affects how a material behaves in extrusion or moulding; the buyer's equipment and product design tolerate a range, and material outside that range causes problems, sometimes immediately and sometimes intermittently. Specifying the window, rather than a nominal value, tells the supplier what the material must achieve and tells the buyer which out-of-window batches are usable.

The window should be established from the buyer's own process — what the equipment can handle, what the product requires, what the operator can manage — rather than adopted from a general specification. A wide window accepts more material and reduces constraints on supply; a narrow window reduces the risk of processing problems but limits the sources available. That trade-off is a commercial decision and it should be made deliberately.

Several characteristics belong in the specification alongside the process window. Colour and its consistency matter where appearance is part of the product and where the buyer cannot adjust. Contamination limits must be stated with the method by which they are measured, because a limit without a method is not enforceable. Moisture content matters for processes where water causes defects or requires drying energy. Odour can be critical for some applications and irrelevant for others.

Test method is the field most often omitted and most consequential. Two laboratories following different methods can report different results for the same material, and a specification that does not state its method cannot be verified. The method should be agreed, and it should be one the buyer can reproduce.

Virgin material is manufactured to a specification, and batches are consistent because the process is controlled. Recyclate comes from a variable input, and even a well-run process produces batches that vary within a range.

That variability is managed in three ways, and all three belong in the supply strategy. The first is specification: stating the range the buyer can accept, so that the supplier knows what to produce and the buyer knows what to reject. The second is testing: checking that batches are within the range, at a frequency that balances the cost of testing against the risk of an out-of-range batch reaching production. The third is the supplier relationship: working with a supplier who understands the buyer's process and can adjust before shipping material the buyer cannot use.

The third is the most valuable and the hardest to establish, and it takes time. A supplier who understands the buyer's process can hold material, blend batches or flag a change before it causes a problem. A transactional relationship in which material is bought and rejected on arrival wastes the buyer's time and the supplier's material, and it produces no learning on either side.

Recyclate supply changes more often than virgin supply, because the input to the recycling process changes. What a supplier can produce depends on what they can obtain, and a change in their feedstock is a change in the material the buyer receives.

That makes change control part of the specification rather than part of good practice. The agreement should establish what the supplier must notify, and what constitutes a change requiring the buyer's requalification. A change of feedstock source, a change of process, a change in the supplier's own supplier — each can change the material, and the buyer should know before it arrives rather than after it has been processed into product.

Requalification is what follows: a defined process by which the buyer assesses the changed material before accepting it into normal supply. It may be as light as a specification check or as substantial as a production trial, depending on the change and the application. The important thing is that the process exists and is applied, rather than being improvised when a problem appears.

One clarification prevents a recurring misconception. Traceability tells you where material came from: which supplier, which batch, which collection source. It is genuinely useful, and it is not a statement about quality.

Material can be fully traceable and still fail to meet a specification, because traceability records provenance and not performance. Conversely, material with incomplete records may perform perfectly. A buyer who treats traceability documentation as evidence of suitability has substituted one kind of assurance for another, and the substitution shows up the first time a traceable batch fails.

Quality is established by testing against the specification for the specific application, and by qualification of the material for that application. It is application-specific, which means the same material may be perfectly suitable for one use and unsuitable for another. Qualification should therefore be against the application — the product, the process and the requirements — rather than against a general grade, and it should be renewed when the application or the material changes.