Why can’t we recycle plastic in the same way we do for metal? Melt it and remold it?
In: Technology
Well, for one, polymers degrade when melted, so you can’t just turn a PET water bottle into a new PET water bottle. It won’t have the same properties anymore. You can use post-consumer recycled PET in something *else*, like a CPET microwave dinner tray, but even then you can’t just use all of it, you can only use a small percentage of it. EDIT: That “something else” can, in fact, be a new bottle, but it will almost certainly be mixed with virgin material and won’t be 100% recycled.
For two, you can’t mix types of plastics, which means that either consumers have to be exceptional at separating their types of plastic (by which I mean the cap *and* ring on your water bottle has to be separated since they’re probably PP while the bottle itself is PET) or we have to have people sort through garbage bags full of recycling to separate it, which adds a hell of a lot to the cost. There’s also the fact that most plastics have some additives in them, for one reason or another, and plastics with certain additives can’t be mixed with others.
For three, any contaminants (adhesives from stickers, residue from food or drink, etc) have to be washed off to the point where they’re as close to completely gone as possible, which is basically impossible and also adds a ton of labor, again increasing the cost dramatically. (This is also true for paper/cardboard – STOP RECYCLING YOUR GREASY PIZZA BOXES, THEY CAN’T BE RECYCLED IF THERE’S FOOD OR GREASE STUCK TO THEM. *Edit: This may not be true, I’m not sure – my city explicitly says not to recycle pizza boxes with grease on them, but YMMV. Maybe someone with more experience in recycling, or paper/cardboard, can chime in on this one.*)
For four, not all plastics are thermoplastics – thermosetting polymers cannot be melted down, they’ll just burn up and release a ton of pollutants into the air. And obviously you can’t mix thermoplastic polymers and thermosetting polymers.
And for five, it’s largely just not feasible to *use* post-consumer recycled plastics because it’s 1) extremely expensive to buy and 2) can be extremely difficult to work into your existing process while maintaining quality and matching the needed performance without using so little that it’s basically irrelevant. You’re paying through the nose to use a tiny amount of the stuff you bought, just to be able to put a label on your product that says “Contains post-consumer recycled material!”
Basically, plastic recycling – while it *is* done to some extent – is ***much*** more limited than the public has been led to believe, and in an amount of cases that would shock the average person, is outright impossible. I guarantee that 80-90% of the plastic items people put in their recycling bin actually end up in a landfill or incinerated because they can’t actually be recycled for a myriad of reasons.
Source: I work in QA at a plastics manufacturer.
This is a great question and one that more people should be asking:)
It start with the fact that not all plastics are the same, there’s all types that can’t be mixed together.
So first off we need a better recycling system. For instance one where you would get money for the plastic waste you turn in. Like you get money for metals you recycle.
Another thing is that with metals, because of the price difference it is neatly sorted. You’ll get a lot more money for copper then for mild steel for instance.
Now to be able to do this we should get better at identifying plastics. You could start by learning how to identify the different types by looking at the recycling triangles!
they should be on every plastic part you have and they can help you id the plastic.
Now, you should also know that not all types of plastic are easily or even cleanly recyclable. But for the ones that are, yes we could melt them and remold them but, like you couldn’t melt copper and steel together, you cannot melt HDPE and PA together:)
If you’re interested in all this be sure to check out Dave Hakkens and the project ‘precious plastic’!
(HDPE is one of my favorites bc you can actually, safely, recycle that in your own oven:)
Not all plastic melts. “Thermoplastic” ones melt when heated, but “thermosetting” ones are made strong by complicated bonds that don’t break down with heat. They will catch fire first.
This is a partial answer, naturally.
Latest Answers