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Comment by wdwvt1 | Hacker News Reader

The exciting thing about this research is that the authors substantially exceeded the normal bar for publishing a scientific article (even one in Nature). They demonstrated industrial feasibility of their proposed enzymatic process by depolymerizing waste PET then repolymerizing it into a useful item (water bottle) that met industry standards for strength/ductility and coloration. I work in microbiology, and seeing research that connects basic biochemistry to actual industrial implementation (at the lab scale) is really impressive. There are pieces of their process that would need to be refined (and the cost of oil would have to rise) for this to be cost competitive with just manufacturing from virgin PET units, but it's a strong foundation. It's much closer to realization than most "researchers discover enzyme that does X and will revolutionize industry Y".

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They're still at lab scale, though. Not pilot plant.

Here's the world's largest PET plastic bottle recycling plant as of 2014.[1] It serves Los Angeles. Plastic bottles go in, and pellets for injection molding of new bottles come out. Along with about 30% trash that came in with the old bottles. If this enzyme is useful, it could become one step in that process. Not clear how much of the cost is in depolymerizing vs. all the other steps required.

Separating bulk recycled materials is pretty much a solved problem technically, but the US was behind in this until shipping unsorted material to China stopped being an option. Robotic sorting is here. The first step was to apply the high-speed vision-based in-fight sorting technology used for fruits and vegetables to recycling. With multispectral imaging, different plastics that look similar to humans can be separated.[2] This isn't experimental; this is what sorts your recycling in most big US cities now. The last 5% of "quality control" sorting, which used to be done in China with cheap labor, is now done with vision-guided robots in the more advanced plants. SF got this last year. At the end of that line, sorted, de-labelled PET bottles are ready for the enzyme or heat processes.

The remaining problems involve cost. It's all do-able.

[1] https://youtu.be/vAr4BZM_Tzk?t=25

[2] https://youtu.be/k2XYA3bXPpo

Wow interesting, thanks for sharing. So should we be trying to recycle plastics again? The news on this changed a lot in the past years. Also there was that whole thing about a bottle cap/ring vs. the bottle itself... do you know what the status is on that?

I think this is already big enough to be the biggest thing about PET for the next few years.

Even if their enzyme is only good enough for 30% round trip efficiency, the benefit of simply doing away with discarded PET is enormous.

Imagine PET having to lay in the garbage dump not for 20-30 years, but for just few month after a day or two in a chemical reactor.

I will add some more comments soon about sorting, and the situation in USA (not going to improve IMHO)

For many applications, it's not necessary to depolymerize PET and repolymerize it. Just grinding it into flakes, cleaning the flakes, melting them down to liquid, and re-casting as pellets is enough.

It doesn't need to be cheaper than virgin PET, it just needs to be cheaper than virgin PET plus the cost of landfill/"recycling". With more countries now refusing to be dumping grounds the cost of getting rid of old bottles stands to rise considerably.

...to the extent that such cost of landfill/recycling is internalized to the producer.

> ...to the extent that such cost of landfill/recycling is internalized to the producer.

It's enough for the costs to be internalized by consumers.

Do you expect a consumer's garbage bill to affect how many and what type of plastic bottles they buy?

> Do you expect a consumer's garbage bill to affect how many and what type of plastic bottles they buy?

Broadly speaking, I think people prefer to spend less money on equivalent goods. So, yes. I do.

I think the effect will probably be less strong than if the entire cost were concentrated at the point of purchase.

I don't mean in the "economics spherical cow" sense, but in the real world.

My garbage company here in Boulder(Western Disposal) determines your fees based on the bin size you have: bigger recycling or trash bins cost more than cheaper ones on an ongoing basis. Compost is free always though.

But really though, there have been weeks where we filled up our bin with lacroixs and beers and I stopped buying canned beverages because of that(for the next 7 days)

That's interesting. Here in Seattle, recycling is free but compost costs money.

They'd have to eat the cost of the more expensive plastic BEFORE their bills would go down, which means it is a decision most consumers will never know to make.

Recycling collection companies will pay them to take the old PET off their hands.

The US is doing more stateside recycling these days, and from this article it sounds like recycling bottles is actually a profitable business.

https://www.theatlantic.com/technology/archive/2015/12/what-...

That was written in 2015.

It is no longer the case https://www.npr.org/2019/08/20/750864036/u-s-recycling-indus...

You may be overestimating the cost of landfills.

Landfill costs (understandably) vary between countries. Got a lot of empty space? Cheap. Crowded? Not cheap at all.

Even in crowded countries, landfill land area is still a tiny percentage.

Its more environmental laws and how strict regulations are about seepage.

Unsorted waste cost is often regulated to be higher than what the immediate costs are. And landfills are banned in a lot of places so the unsorted waste has to be resorted and the uncrecycleable parts incinerated[1].

[1] eg see third column of table 3.1 at https://www.eea.europa.eu/themes/waste/waste-management/muni...

Some European countries have essentially banned landfills; waste must be either exported (expensive, increasingly difficult), recycled (expensive) or burned (expensive, controversial).

It needs to be cheaper than cost of ‘virgin PET’ including the taxes levied on the material itself, technically. I haven’t done the math to incorporate the tax duties of the hydrocarbons used to form non-recycled PET but I assume currently most countries levy no tax whatsoever on PET itself, regardless of source?

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