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Three complaints account for most rejected deliveries of post-consumer recyclate: it smells, the colour has moved since the last batch, and there are gels or unmelted particles in the part. Each of them is usually treated as a supplier failure. Each of them is more often a specification failure, because the contract never said what “acceptable” meant. All three trace back to something the input stream did, and all three could have been settled in advance by a clause naming a reference sample and a test method.
Odour: absorbed, not surface
Polyolefins absorb what they contain. A detergent bottle spends a year holding fragrance and surfactant, and some of that migrates into the polymer wall. Washing removes what is on the surface. It does not remove what is dissolved in the material.
Odour therefore tracks the input stream more than the washing line. Household chemical streams carry fragrance. Food streams carry degradation products from residues. Mixed commercial streams carry whatever they carried. A recycler can reduce odour with devolatilisation during extrusion and with tighter input selection, but cannot eliminate the history of the material.
What to put in the contract: a sensory assessment method, an agreed reference sample, and the panel or scale that will be used to judge it. “Neutral odour” is not a specification, because two people will read it differently and neither reading is testable.
Colour drift: the input mix moved
Batch-to-batch colour variation is the most common complaint and the least avoidable one. A recycler does not choose the colour of the material arriving at the gate. The proportion of blue to green to natural bottles in a bale changes with season, region and collection scheme, and the output shifts with it.
This is also where most money is lost, because colour decides which grade a material can be sold as. At the end of June 2026, grey rHDPE pellets were assessed at 1,111 to 1,121 euros per tonne against 1,705 to 1,715 for natural, delivered duty paid to Northwest Europe. Roughly 600 euros per tonne separates two grades of the same polymer, and the only difference is what the sorter could pull out.
What to put in the contract: a retained reference sample, a measurement geometry, and a tolerance expressed as a colour difference against that reference rather than as an adjective. Agree in advance whether the tolerance applies per batch or as a rolling average across deliveries, because those two readings produce very different rejection rates.
Gels and unmelts: usually another polymer
A gel in film or a hard particle in a moulded part is normally one of three things: a fragment of a different polymer that did not melt at your processing temperature, a piece of over-degraded material that cross-linked, or a filler or label residue that survived washing.
The first is the most common, and it is a sorting question rather than a compounding one. Polypropylene in a polyethylene stream, or a barrier layer from a multilayer pack, behaves as a solid inclusion at PE processing temperatures. No amount of screw configuration fixes material that is not supposed to be there.
What to put in the contract: the melt filtration stage the material passes through and the screen used, plus an agreed method for counting inclusions. Thin film shows every defect and tolerates almost none. A thick-walled crate hides most of them. The specification should say which application it is written for, because a gel count that is unacceptable for film is irrelevant for a pallet.
Turning the complaint into a clause
The pattern behind all three is the same. Post-consumer material is variable by nature, and a specification that pretends otherwise fails at the first seasonal shift in the input stream. A specification that names the variation and sets a tolerance around it survives.
Three questions produce most of the value. Against what reference is this judged? By what method? And is the tolerance per batch or across a period? A supplier who is asked those questions can price the answer. A supplier who is asked for “consistent quality” will quote for the easiest interpretation of it, and the argument arrives later at the goods-in bay.
The grade differences behind these decisions are set out in our introduction to post-consumer recyclate, and the price context in the June 2026 price assessments. For the sourcing picture as a whole, start from our post-consumer recyclate overview.
Frequently asked questions
Why does recycled polyolefin smell?
Because polyolefins absorb substances they hold during service life, such as fragrances and surfactants from household chemical bottles. Washing removes surface residues but not what has migrated into the polymer.
Can a supplier guarantee identical colour between batches?
Not reliably, because the colour mix of incoming material changes with season, region and collection scheme. What can be agreed is a reference sample, a measurement method and a stated tolerance.
What causes gels in recycled film?
Most often a fragment of a different polymer that does not melt at the processing temperature used, and less often over-degraded cross-linked material or filler and label residue that survived washing.
How much does colour affect the price of rHDPE?
Substantially. At the end of June 2026, grey pellets were assessed at 1,111 to 1,121 euros per tonne and natural pellets at 1,705 to 1,715, delivered duty paid to Northwest Europe.
What is the single most useful clause in a PCR specification?
A named reference sample with an agreed test method and a tolerance that states whether it applies per batch or as a rolling average across deliveries.