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Comment by amluto | Hacker News Reader

If this works on a feedstock of mixed, dirty plastics, I can imagine it actually being economical.

Imagine throwing a bunch of waste plastic in a reactor. Some is PET. Some is HDPE. Some is polycarbonate. Some is polystyrene. Some is other random polymers. Some is “compostable” material, and some is probably a horrible mix of plant fiber and fluoropolymers. Some is bamboo that got mixed in by accident, and there’s also some bits of food and crayons and other debris in there. Add a mix of enzymes and apply the right temperature, humidity, etc.

Out comes a mix of valuable monomers, various contaminants, and the enzymes that survived the process. And a whole lot of unreacted feedstock that simply wasn’t the right feedstock.

If you can separate the valuables out of the output mix, then maybe this whole enterprise pays for itself.

Otherwise actually obtaining a clean stream of PET to recycle seems potentially challenging.

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What you are describing could be the starting point for a processing plant that mimicks a digestive system. Plastics are moved via peristalsis through a series of physical and chemical incubators, extracting elemental substances through membranes along the way. Out comes the unusable, uhm, ash, that needs to be discarded.

https://en.m.wikipedia.org/wiki/Anaerobic_digestion

Many other countries have no problems at all separating plastics. If you want it done well in America you probably just need to add a small refundable deposit to every recyclable container. But much bigger than the inflated to nothing 5 cents of soda containers.

Even well sorted plastics will still have food scraps attached, except in locations where it makes environmental sense to have people wash it first.

The issue is that recycling plastics uses quite a lot of energy in itself, so it quickly becomes a net-negative over not recycling with current technologies, especially if you use a lot of tap water and generate a lot of wastewater cleaning it.

Yeah, unfortunately that energy is currently, like plastics made from fossil fuels, so the same people paid to tell you recycling uses too much energy are the same people telling you that renewables don't work. It's almost like they want people to use more of the fossil fuels they sell.

Because it is an enzyme, it will have a relatively high specificity of action (it will not act on a different target) and as it decomposes the stuff in a nice clean molecule[0], this should work. Except of course if you pour in the mix something neutralizing the enzyme.

At the end, you always need to separate, the process engineers will have to figure out what is the best method (washing, crystallization, distillation or direct reaction to build longer polymer chains, ...).

[0]: https://www.chemeo.com/cid/54-117-2/Terephthalic-acid

This already exists, though with a different process: https://www.powerhouseenergy.co.uk/

We can just ship these enzymes in bacteria into garbage dumps and that plastic island in the ocean. Could be a one time cost

Enzymes do not reproduce

I think the reference to bacteria was suggesting bacteria that produce the enzyme, though that isn't clear from the post. Of course there's a lot involved in creating a viable bacterium that can survive in the wild on plastics than just making one produce this enzyme though.

The powerline isolation, it has been eaten, the good thing, anyone can cook such a thing up. so its a minority veto voting on progress world we are now in today.

That’s proper stuff from nightmares. Imagine a bacterium so viable, it gets out of control and reproduces massively, because there is so much tasty plastics everywhere. Say goodbye to the modern world.

Bacteria eat wood already and we still use it, what's the problem?

That we didn’t engineer those bacteria to be massively effective in a short amount of time.

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