Feedstock Quality Parameters & Business Impact
Six feedstock quality parameters that determine depolymerisation plant profitability — polymer purity, moisture content, PVC contamination, bulk density, ash/dirt content, and organic residue — with ideal ranges and business consequences.
Parameter | Ideal Range | Impact on Business |
Purity (Polymer %) | > 95% | Higher purity means less waste "sludge" to dispose of and higher monomer yield. |
Moisture Content | < 2% | High moisture wastes energy (evaporation) and can cause "foaming" inside the reactor. |
PVC Contamination | < 0.1% | Anything higher will corrode your reactor walls and "poison" your chemical catalyst. |
Bulk Density | 250 – 400 kg/m^3 | Heavily compressed (baled) waste reduces transport costs and fits better in the feeder. |
Ash/Dirt Content | < 1% | Sand and grit act like sandpaper, wearing down your pumps and valves. |
Organic Residue | < 0.5% | Food or sugar residue chars at high heat, turning your final product "brown." |
Beyond definitions
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How to read this table
- Each row is one quality parameter; Ideal Range is the specification to purchase to; Impact on Business describes what happens if the spec is not met.
- PVC Contamination has the most severe consequence (catalyst poisoning) — it is the deal-breaker parameter that should be tested on every incoming lot.
- Bulk Density is the only parameter where higher is better — denser feedstock means lower transport cost and better reactor feeding.
About this table
In a depolymerisation plant, feedstock quality is not just a technical concern — every deviation from specification has a direct commercial consequence. This table connects each of six key quality parameters to its ideal range and the specific business impact of running below that standard, giving operators and procurement managers a clear picture of what they are buying when they accept a feedstock lot.
Purity (polymer percentage) above 95% is the baseline target. Higher purity means less waste sludge to dispose of after the reaction and higher monomer yield per tonne of feedstock — both of which directly improve revenue per tonne processed. Every percentage point of purity below 95% effectively transfers value from monomer output to disposal cost. Moisture content below 2% is required because excess water wastes energy (it must be evaporated inside the reactor, consuming heat without producing product) and can cause foaming that disrupts reaction control and produces low-quality crude monomer. Most incoming waste streams — especially post-consumer textiles and mixed bales — need pre-drying investment to meet this spec.
PVC contamination below 0.1% is the strictest specification because PVC releases hydrochloric acid during depolymerisation reaction temperatures, poisoning the catalyst and corroding the reactor. Bulk density of 250–400 kg/m³ is the target for efficient reactor feeding — heavily compressed (baled) waste fills the feeder efficiently and reduces transport cost per tonne. Loose or uncrushed waste below 200 kg/m³ is expensive to transport and difficult to feed continuously. Ash and dirt content below 1% protects pumps and valves from abrasive wear — sand and grit in the feedstock act mechanically on seals and impellers. Organic residue (food, sugar, biowaste) below 0.5% prevents charring inside the reactor at high temperatures, which would discolour the monomer product and require additional purification steps.
Key insights
- PVC contamination above 0.1% poisons the catalyst and corrodes reactor walls — it is the highest-risk quality parameter and should be tested on every incoming load, not only on sampled lots.
- Moisture above 2% wastes energy on evaporation and causes reactor foaming — pre-drying is an operating investment that pays back through yield improvement and reduced purification cost.
- Bulk density of 250–400 kg/m³ (typical for compressed bales) reduces transport cost per tonne and enables consistent reactor feeding — accepting loose, uncompressed feedstock inflates both logistics and operational costs.
- Organic residue above 0.5% causes char formation that discolours the monomer output — even a small brownish tint in the monomer can disqualify it from food-grade or textile-grade markets.
Methodology & sources
Quality parameter ranges are based on typical depolymerisation (glycolysis, hydrolysis) process specifications for PET and related polymers as of 2024. Actual specifications vary with reaction chemistry and target monomer purity grade. All incoming feedstock lots should be sampled and tested against these parameters before purchase authorisation — post-delivery price adjustments for off-spec material are common in feedstock supply agreements but poor quality still incurs processing cost.
Related data tables
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.
Feedstock Cost vs. Yield by Type
A comparison of four PET-type feedstocks for depolymerisation — clear bottles, coloured PET, polyester textiles, and multi-layer packaging — showing estimated yield percentage, cost profile, and the reason for yield loss in each case.
Maximum Contamination Tolerance Levels
Maximum contamination tolerance levels and technical solutions for four key contaminants in depolymerisation feedstock — PVC content, moisture, other polymers, and ash/dirt — the go/no-go specifications for feedstock acceptance.