Some thoughts, potential solutions, and a bit of education
Good stuff, and an interesting perspective. Based on what I've studied with chemcycling, I think we'll be seeing a lot of policies in the near future (especially within the EU) that will help the economics. Policies like requiring a minimum % of recycled plastic can help the economics of chemcycling drastically as the recycled plastic should command a hefty premium.
I think we'll also see PS chemcycling become more used. I believe Indaver P2C + INEOS Styrolution is starting to test PS chemcycling, and the literature seems to suggest that pyrolysis is quite effective in obtaining the styrene monomer (50%+ yield i think), with contamination/separation remaining a huge challenge. What's great about PS compared to PE/PP is that you don't have to go via the long-chain HC → steam cracking route, whose heavy footprint really makes PE/PP chemcycling hardly environmentally beneficial.
But yeah I think none of this will be possible without policies on companies to design inherently recyclable plastics -- none of the paper-plastic films or multi-compositional plastics. It's frustrating how much contamination from paper, organic materials, metals are in everything, and that's nothing the consumer can do really...
This is a nice summary, Tony.
I think there is a lot of promise in PET-to-monomers technology (i.e., regenerate TPA and EG) which can generally deal with contaminants pretty well (filtration) but is of course more energy-intensive than conventional processes. For other commodity polymers, there's not much you can do, and for stuff like PE, PP, or PS you either mechanically recycle it until it has no value, or pyrolyze it to oils / waxes, or burn it to generate energy.
There's lots of work going on in academia related to chemical recycling, but from what I can tell, it is focused in inventing new polymers that are more tractable. Some of the ideas are quite clever, but I don't actually think this approach is a good solution to the problem, at its current scale.
One of the really big and often overlooked issues (which you touch on) is the complexity of the waste stream. Caps, liners, multi-layer packaging, pigments, additives, etc. are a big barrier (no pun intended) to any type of recycling. This can create some interesting conundrums. Our family likes to buy frozen vegetables and fruit (think broccoli, mango pieces, etc.) and we find that we waste a lot less food that way. But the stand-up pouches they come in are multi-layer (I believe PET and PE) and not recyclable here.
Even simple things like printed labels or dyes can be a problem. The common green pigment used in plastics is Pigment Green 7, which is perchlorinated copper phthalocyanine. It's more than 50% chlorine by weight. What do you do with it?
At the end of the day the old saw "reduce, reuse., recycle" still has a lot of merit. I think effort expended on redesign for reduction and reuse of polymer materials would have a lot more value to society than effort expended on recycling. But that's my two cents....
Tony -- This does a brilliant job of explaining the process issues in language that is accessible to lay people. Thanks for doing this!