Eli5 why are so few plastics recyclable? Why cant you just melt it down and reuse it like glass?
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So I’m actually a chemical engineer at a polypropylene plant. When we make plastic for customers there’s very specific characteristics of the same polypropylene plastic depending on application. Some plastic it’s okay for it to shatter/fragment on impact – think a rigid plastic tub. Other plastic you want to “bend” or take an impact: ie your car bumper. This plastic – though all polypropylene have different molecular weight distributions, crystallinity, etc that we control during the reactor process (when we take propylene and react with a catalyst = polypropylene). Now you’re left with a bunch of fluffy non uniform plastic with given specs. We then take that, extrude it, add a bunch of additives depending on the customer – customer wants white pellets? Customer wants plastic that’s see through? Cusomter doesn’t care? All different additive packages that get added into the extruder. The extruder then mixes it all up in one gooey mixture, pushes it through holes like play dough and cuts it into perfect little round pellets for our customers to use for whatever application.
Now imagine trying to recycle this plastic. Even with it all being polypropylene, if you mix all this plastic together – car bumpers, pill bottles, etc. it’s very difficult to get a product that have the same specific characteristics that the virgin polymer has. Sorting it to even get close (i.e. all at least the same plastic type) is expensive and way pricier than the virgin stuff and lesser quality. We’re struggling now to get customers to pay the extra premium for our recycled plastic (my company is doing it in specific markets). But to do it we have to find for example a company that recycles just PE (polyethylene). This company does all the sorting for us. We pay them for that plastic. Then we could feed it into an extruder with virgin polymer or whatever and produce something new. This product is pricier than just straight virgin. Our customers aren’t biting yet. It’ll take consumer pushing for certain percentages of recycled plastic in products to incentivize companies to pay the extra dollar for recycled goods.
Not speaking for industry or anything. Just work for a big petrochemical company and this is my unique perspective actively working as a chemical engineering manager at the polypropylene plant.
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