Enzymatic degradation, recycling, and upcycling of movable crosslinked polymers | Hacker News Reader

Enzymatic degradation, recycling, and upcycling of movable crosslinked polymers

cell.com

36 pointsPaulHoule9 comments

A biologist once told me "enzymatic degradation of PET is like the fusion power of biotechnology".

There already are enzymes that degrade PET. Some of them are engineered, some are naturally sourced from fungi (maybe also bacteria)

The challenge for wider adoption of this tech (as in most things in biology) is the upscale. The cost of collecting, cleaning the feedstock, producing the enzymes and essentially running the bio-factory is much higher than the output material, which in the case of PET hydrolysis is terephthalic acid (TPA) and ethylene glycol.

Even when considering that the monomers can be polymerized back to PET and complete the cycle, but the price of PET is so cheap, that this is still economically inviable.

As in always N years away, for a certain constant N?

I think so, yes.

All schemes for chemical plastic recycling are challenged by the fact that plastic monomers and other chemicals you might get from breaking down plastics (say in a disordered process such as pyrolysis) are worth about 50 cents a pound.

You cannot afford $50 of enzymes to make 50 cents of product but it's likely to be like that. Chemical recycling of polystyrene has been technically practical since the 1970s but the cost of bringing all that bulky styrofoam to one place defeats the economics.

Landfill disposal is a few cents per pound, any subsidy has to be huge to move the needle.

If I'm reading this right, they were able to build a certain kind of polyurethane that is easier for enzymes to break down. Neat, but won't do much to help recycle any plastic that has already been manufactured, I'm afraid.

My understanding is that we have a lot of such "compostable" materials. However, they don't have as good properties as "plastic" and so they aren't visibly replacing them. Once we manage to get similar in structure and costs then it's a good start to replace.

If we could 1) create plastics from plant materials 2) recycle them using the techniques in the paper above 3) build in a limited lifetime so that plastics don't sit around forever and 4)have usable plastics that don't need plasticizers that mess with living organisms then plastic has a future. Otherwise we need a different material.

A journal reaching top of Hackernews? What is this?

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