Feedstock Acceptance/Rejection Criteria
A four-parameter feedstock acceptance decision table for a depolymerisation plant — showing Acceptable, Conditional (with price discount), and Rejected thresholds for PET content, PVC contamination, moisture, and colour.
Parameter | Acceptable | Conditional (Price Drop) | Rejected |
PET Content | > 98% | 90% - 97% | < 90% |
PVC Content | 0% | < 0.1% | > 0.1% |
Moisture | < 2% | 2% - 10% (Requires Drying) | > 10% |
Color | Any Color | N/A | Mixed with Rubber |
Beyond definitions
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How to read this table
- Acceptable means the lot is purchased at the agreed specification price.
- Conditional (Price Drop) means the lot can be accepted but triggers a negotiated price reduction to compensate for additional processing cost or yield impact.
- Rejected means the lot is not purchased and must be returned to the supplier or disposed of separately.
- All parameters should be tested on each incoming lot — do not assume a known supplier consistently meets specification without testing.
About this table
The feedstock acceptance process at a depolymerisation plant gate determines the quality of everything that follows — and it must be fast, consistent, and commercially defensible. This table codifies the three-tier decision framework: material that is Acceptable (full purchase price), Conditional (accepted but at a negotiated price reduction to compensate for additional processing cost or yield loss), and Rejected (returned or disposed at supplier's cost).
PET content is the primary value parameter. Above 98% PET content, the material is accepted at full price — losses are minimal and monomer yield is maximised. Between 90–97%, the material is conditionally accepted with a price reduction that reflects the additional pre-treatment and yield loss. Below 90%, the non-PET fraction is large enough to make processing economically unviable — the lot is rejected. PVC content has the strictest rejection threshold of any parameter. Zero PVC is the ideal; below 0.1% is conditionally acceptable because the reactor can tolerate trace levels with additional monitoring. Above 0.1%, the lot is rejected because even that level of PVC can begin to degrade catalyst performance over time, and the risk-reward of accepting it is unfavourable.
Moisture content up to 2% is acceptable without adjustment; 2–10% is conditional because it requires pre-drying before processing — the additional energy cost justifies a price reduction. Above 10%, the cost of drying plus the energy waste is too high relative to the feedstock value. Colour is notable for being the most permissive parameter: colour does not affect the depolymerisation reaction chemistry or monomer yield — one of the key advantages of depolymerisation over mechanical recycling. The one absolute rejection condition for colour is mixing with rubber — rubber does not depolymerise cleanly and creates disposal problems that outweigh any feedstock value.
Key insights
- PVC rejection at 0.1% is a hard operational rule, not a commercial preference — accepting above-spec PVC is not offset by any price discount because catalyst poisoning is irreversible.
- Colour is accepted in any form except when mixed with rubber — depolymerisation's colour-blindness is a structural advantage over mechanical recycling for coloured waste streams.
- Moisture between 2–10% is manageable with on-site drying, but the cost of that drying must be reflected in the conditional price — a well-structured supply contract will specify the pre-drying deduction formula.
- The three-tier structure (Acceptable/Conditional/Rejected) enables consistent gate-level decisions without requiring management escalation for every marginal lot.
Methodology & sources
Thresholds described represent typical operational criteria for depolymerisation (glycolysis/hydrolysis) plants processing PET feedstock as of 2024. Actual thresholds should be set in consultation with your technology licensor and adjusted based on actual catalyst sensitivity data. Price reduction formulas for Conditional material are commercially negotiated and vary between supply agreements.
Related data tables
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