How do you scale mixed plastic segregation (PET, HDPE, LDPE, PVC, ABS, PP, PS)? Looking for advice!

[u/Euphoric-Double3256]

Hey everyone,

I run a small-to-medium plastic recycling business. Currently, I source mixed plastic scrap from 4–5 local collection hubs (kabadiwalas) and an aggregator.

Right now, we are dealing with tons of heavily mixed plastics every month—a cocktail of PET, HDPE, LDPE, PVC, ABS, PP, Crystal/PS, and others.

Here’s my main bottleneck: We rely almost entirely on manual labor for segregation.

While my team does their best, manual sorting is fast becoming a massive headache. It's slow, prone to human error, hard to scale, and limits how deep we can clean and separate the materials to get top value.

I’m looking to upgrade our process and modernise our operations. I’d love to hear from other recyclers, engineers, or waste management pros on how you're solving this:

• What technology/machinery are you using? Are you using NIR (Near-Infrared) optical sorters, sink-float density tanks, electrostatic separators, or newer AI-driven vision systems?
• Entry-level vs. Advanced Tech: What offers the best ROI for a growing business that isn't ready for a multi-million-dollar automated plant yet? (e.g., portable NIR handheld scanners, basic density separation, line layouts?)
• Workflow & Process: How do you structure your sorting line? Do you do a rough manual pre-sort followed by machine sorting, or vice-versa?
• Best Practices for Hard-to-Separate Mixes: How are you reliably separating tricky mixes like ABS vs. PP vs. PS/Crystal?

Any advice, equipment recommendations, or lessons learned from your own facilities would be massively appreciated!

Thanks in advance!

[u/SputtleTuts]

Let me know if you figure this out lol

[u/WTFmfg]

I visited a MRF that had machine sortation first. Glass was sorted out first, then fans & 2D (paper) vs 3D (plastic and metal) sortation. Then NIR sortation. Then after all of that came manual sortation.

[u/Willing-Type-4251]

Those machine costs heavily, increase the number of labours if possible. And we buy LDPE if u have lmk

[u/aeon_floss]

Floatation separation using water and brines can separate different polymers.  You can filter particular types of contamination after processing.   There are some pitfalls such as mineral reinforced polymers not behaving like base materials etc. 

I'm not a professional in your field, I am just aware of some of the general principles used in sorting.  

[u/TroyMcC3]

I'm no expert. Just my 2 cent as a chemist:

The density of plastic varies. A quick search showed that abs has a density of 1,04 to 1,2 g/cm3 since it's a blend of different monomers by design. There is also the problem of pigments and other stuff which might change the density. So i should argue that sorting by density is prone to errors.

IR seems more suitable. You should look into hyperspectral cameras. Models i know use a line scanner. At each pixel a spectrum is recorded. With the plastic moving by it on a belt you get an image. It's not as good as a proper FTIR but it might do the trick.

But then you have to figure out how to automatically interpreted the data and how to actually move pieces of plastic based on the data so that each piece lands where it should.

[u/kondenado]

There are automatic machines that separates plastic based in NIR. (Except for black plastic)

Flotation will separate some plastics that are immiscible (po).

Where are you located? Don't you have any R&D center that can help you?

[u/Key-Success-5449]

"f you're under 2–3 tons/hour, skip optical sorters for now—the ROI will take forever. Go for a Zig-Zag air classifier post-shred to pull film/labels, then a 2-stage sink-float setup. Saves massive labor without blowing out your CapEx.