When we bought the granulator in 2017 I modelled the regrind as a single commodity at a single price. That was wrong in a way that turned out to be worth about $43,000 a year.
What a regrind buyer is actually buying
An extruder making drainage pipe, pallet blocks or agricultural ducting is not buying "recycled plastic". They are buying a feedstock that has to behave predictably in their process, and two properties govern that.
- Colour. Natural — uncoloured HDPE — can be pigmented to whatever the end product needs. Mixed colour can only go into products that are dark or where appearance is irrelevant. That restricts the buyer pool dramatically.
- Melt flow index. How the polymer flows at temperature. An extruder tuned for a narrow MFI band cannot absorb material that varies run to run without re-tuning, and re-tuning costs more than the material saves.
The premiums
| Specification | Relative price | Typical buyer |
|---|---|---|
| Mixed colour, mixed MFI | baseline | Dark products, pallet blocks, filler |
| Mixed colour, consistent MFI | +8% – 12% | Drainage pipe, ducting |
| Natural, mixed MFI | +18% – 22% | Pigmented products, general moulding |
| Natural, consistent MFI | +28% – 34% | Specified extrusion, higher-spec moulding |
| Natural, consistent MFI, certified source | +36% – 42% | Buyers with recycled-content targets to evidence |
Indicative regrind pricing relative to mixed-colour baseline
That bottom row is newer and it is growing. Buyers with recycled-content commitments increasingly need to evidence where the material came from, and an IBC bottle with a documented prior-contents history is unusually well evidenced compared with kerbside stream material.
Why IBC bottles are good feedstock
Three structural advantages over most post-use HDPE.
- Thick wall, single material. An IBC bottle is one polymer with no labels fused to it, no multilayer barrier, no dissimilar closures attached if you strip them first. Kerbside HDPE is none of those things.
- Known history. We know what was in it because we collected the disclosure at intake. A buyer concerned about residual contamination can see the prior-contents record.
- Consistent origin. A batch of bottles from one filler is effectively one resin grade, so MFI consistency within a batch is high before we do anything.
There is a fourth that matters less commercially and more practically: the parts are big. A 275-gallon bottle cuts into large, flat, easily handled sections. Kerbside HDPE arrives as a mixed stream of small awkward shapes with closures and labels attached, and the sorting cost per tonne is an order of magnitude higher.
The contamination reality
Buyers are far less tolerant than I expected. A single polypropylene valve body granulated into a 500 kg batch of HDPE will show up as inclusions in extruded pipe and the batch gets rejected.
| Contaminant | Source | Effect if granulated in |
|---|---|---|
| Polypropylene valve body | Discharge valve | Inclusions, batch rejection |
| EPDM or Viton gasket | Lid and valve seals | Black specks, surface defects |
| Steel strap or fixing | Bottle retention | Equipment damage, metal detection failure |
| Paper or foil label | Filler labelling | Carbonises and discolours |
| Residual product | Incomplete draining | Odour, clumping in the hopper |
Contaminants we remove before granulating, and why
That is why disassembly matters. Shredding a whole tote mixed — which is exactly what a general scrap contractor does — destroys the value of all three streams simultaneously: contaminated plastic, plastic-contaminated steel, and no sorting at all.
A scrap contractor is optimising throughput. We are optimising the material. Those produce different machines and very different prices.
What it did to the payback
We modelled the granulator at a mixed-stream price and got a 4.5-year payback, which I presented as marginal and we approved anyway for traceability reasons. Sorting to colour and MFI pulled it to 3.2 years.
The additional cost of sorting is one person-hour per tonne and a few storage bays. It is the highest-return process change we have made, and we made it by accident — the first natural-only batch happened because a single filler sent us 200 identical units and the bay was full.
If you are disposing of containers
The practical takeaway for anyone holding end-of-life totes: a scrap contractor will pay you shred price for a mixed shred. That is a legitimate transaction and it is roughly a third of what the separated streams are worth.
- Separate the units by prior contents if you can. Same-filler batches are worth more.
- Do not shred. Whole units are worth more than shred because the buyer can disassemble properly.
- Keep the paperwork. Documented origin is now a priced attribute, not just a compliance artefact.
- Ask for the tonnage on a certificate — see diversion reporting.
What happens to each stream is set out on our recycling page.
Written by
Theo Marsh
Materials & reporting
Owns the granulator, the baler and the diversion certificates. Writes the carbon methodology and defends the coefficients.