Photo: Gaurav Ranjitkar / Pexels
A plastic recycling line starts with two specifications: the waste available and the material a customer will accept. Clean PP production scrap, dirty PE film and used PET bottles need different preparation. Buying a shredder and an extruder does not establish that the resulting pellets will meet an injection moulder or film producer's requirements. Work backwards from that customer's specification, then select the operations needed to achieve it.
Regrind, flakes or pellets: what are you actually selling?
An industrial plastic shredder reduces size; it does not automatically clean or homogenise the material. A cutting granulator produces regrind through a screen. A pelletiser cuts polymer after melt extrusion. Suppliers sometimes use « granulator » loosely, so specify the output form, size distribution, moisture and composition rather than comparing machine names. If your buyer accepts washed flakes, a washing line can be a complete project without pelletising.
| Feedstock | Possible output | Configuration to investigate |
|---|---|---|
| Clean, identified PP or PE production offcuts | Regrind returned to a compatible process | Sorting, metal detection and screened granulation; extrusion only if the downstream process requires it. |
| Contaminated post-consumer PE film | Pellets qualified for a defined application | Preparation, washing, dewatering/drying, film-compatible feeding, filtered and degassed extrusion, pelletising. |
| PET bottles with labels and caps | Washed flakes or rPET pellets | Sorting, size reduction, washing, separation and drying; PET treatment and extrusion if pellets are required. |
Which machines do what?
- Receive, sort and remove unwanted material
- Pre-shred where needed, then granulate
- Wash and separate where required
- Dewater and dry to the next process specification
- Extrude, filter and degas
- Cut, cool and check each output lot
This is one route to extruded pellets, not a compulsory sequence for every waste stream. A pre-shredder makes bulky parts manageable; a knife granulator and screen control regrind size. Washing removes accessible contamination, while separation removes incompatible fractions. Drying prepares the feed for the next operation. Extrusion melts the polymer, melt filtration retains some solid contaminants, degassing removes some volatile compounds, and pelletising forms the final particles.
Herbold: washing, separation and drying components explained
Is washing necessary, and can PE, PP and PET be mixed?
Clean, segregated production scrap may bypass washing if it meets downstream requirements. Soil-laden agricultural film needs appropriate preparation: feeding abrasive dirt into cutting equipment increases wear risk. A melt filter cannot replace polymer sorting, because another polymer may melt and remain in the material. Qualify a proposed mixed-plastic product with its intended customer rather than assuming a general-purpose recycling machine makes all plastics compatible.
PET also requires control of moisture and intrinsic viscosity for the intended processing route. EREMA's bottle-to-bottle documentation distinguishes decontamination, drying and viscosity treatment. Visually clean pellets alone do not establish food-contact suitability: the process, permitted inputs and compliance of the intended use require validation.
EREMA: PET bottle-to-bottle treatment and output requirements
How do you calculate useful throughput?
Illustrative calculation, not an MSR performance claim: processing 120 incoming tonnes per month over 20 eight-hour days gives 160 scheduled hours. At an assumed 75% availability, there are 120 running hours, requiring 1 incoming t/h while operating. An assumed 80% saleable yield gives 96 saleable tonnes/month, or 0.8 t/h during operation. Replace both assumptions with your trial results.
A quoted tonne per hour of wet incoming waste is not the same as a tonne per hour of compliant pellets. Define the weighing basis and verify every stage against the same feedstock. Feeding, washing, drying or filter changes can constrain the whole line even when the shredder has enough capacity. Motor power alone does not establish production.
| Measure | Basis for comparison |
|---|---|
| Useful throughput | Compliant output mass divided by the agreed total period; identify stops and filter changes. |
| Material yield | Compliant product / input on a defined basis; record water, dirt, other polymers and rejects separately. |
| Electricity and water | Whole-line kWh per compliant tonne; make-up water and discharged water, not just recirculation flow. |
| Lot quality | Polymer, moisture, contamination, colour, odour and application properties such as MFR/MFI or PET intrinsic viscosity. |
What should the recycling line quotation include?
Request separate prices for main equipment, conveying, sorting, washing, water circulation/treatment, drying, extrusion, filtration, silos, electrical connection, civil works, freight, installation, commissioning and initial spare parts. State exclusions and customer-supplied services. An advertised standalone plastic recycling machine price cannot establish the cost of an installed line processing your actual feedstock.
Compare cost per accepted tonne: annual investment charges, labour, electricity, water, consumables, maintenance and reject treatment divided by output accepted by customers. Include feedstock purchase and transport where relevant. Test sensitivity to lower pellet prices, lower supply and rejected lots before deciding whether extrusion adds value over selling washed flakes or regrind.
Use the complete project brief for layout, operations and acceptance
What proof should you request before ordering?
- A representative trial using your waste, including realistic moisture and contamination, with output criteria agreed beforehand.
- Weights for every output fraction, lot samples and acceptance of a sample by the intended converter.
- Net throughput, trial duration, whole-line energy, filter changes, cleaning and downtime.
- A layout covering maintenance access, utilities, water, extraction, noise and storage.
- Supply boundaries, site acceptance criteria and prices/lead times for knives, screens and filter elements.
MSR Environnement works with plastics recyclers. Send the polymer identity, photographs and samples, monthly tonnage, moisture, unwanted material and intended product specification. These make an equipment study and comparable trials possible; they do not themselves guarantee yield.
Discuss my plastic recycling line with MSR