Scientists break down plastic using a simple, inexpensive catalyst and air

Of course there are always reasons. But as long as the costs of recycling are not borne by businesses doing the packaging, the business will always go with the 1 cent cheaper option, even if it makes recycling 100 times harder.

So what might square this circle is to develop several materials that all can be broken down/recycled by a common process.

Far easier said than done, I'm sure. But someone has to say it before it can happen.

This is actually one of the use cases the authors discuss in their paper. Sending mixed plastics through this process to extract the PET/PBT containing bits, and send the rest along their way.

When the team tested the process on real-world materials like plastic bottles, shirts and mixed plastic waste, it proved just as effective. It even broke down colored plastics into pure, colorless TPA.

-- the article

so that's good I guess

Only in some ways. Mostly it’s due to use case and desired characteristics of the container, one of which can be cost. As another poster noted, different products need different packaging solutions.

"Because money" always boils down to "because it requires a lot of resources".

It's not about random pieces of paper with numbers.

Among other problems, plastics release methane and c02 as they decompose in landfills, so it's not as cut and dried a solution as you imply.

That was always my impression, and after that you can always build a park on top!

The temperature at which burning polymers completely eliminates particulates and CO is very close to the temperature that NOx starts to form.

Source: I did a bunch of research on rocket mass heaters (think rocket stove, not missile engine) when I built one.

The reference: https://en.m.wikipedia.org/wiki/Amager_Bakke

Mixed plastic is definitely impressive, but how is it separated? I imagine a lot of it must be done by hand? And then washed with water? Seems both labor intensive and energy intensive

Apparently 95% of the test sample can be recovered. If its dirty and mixed, how much can TPA can be recovered and is the sludge chemically inert and landfillable?

Always seemed like greenwashing to care about the straw in the drink that’s on a plastic cup with a plastic lid from the beans shipped in a plastic bag and render the experience of trying to drink it as tedious as possible.

Yes PET (#1) and HDPE (#2) are the two easiest plastics to recycle and the most commonly recycled

But fabrics are the best way of putting super hard to track microplastics in water and in the air. We drink them and inhale them

This is contrast to the pyrolysis-based "chemical recycling of plastics" which makes a mix of petrochemicals similar to what you find in the BTX stage of a petrochemical factories [1], especially for condensation polymers like PET. That is, this process produces fairly pure Terephthalic acid [2] and Acetaldehyde [3] and the first of those could be recycled into more PET.

The thing is BTX chemicals and other precursors of mass produced plastics cost about 50 cents a pound which makes it hard for any kind of recycling process to be competitive.

[1] https://en.wikipedia.org/wiki/BTX_(chemistry)

[2] https://en.wikipedia.org/wiki/Terephthalic_acid

[3] https://en.wikipedia.org/wiki/Acetaldehyde

That's within the range of a kitchen oven. The biggest problem is that plastic is so cheap that even that relatively modest energy use may make it uneconomic compared to virgin TPA, especially if you have to clean the inputs thoroughly first.

The authors' claim is that it is cheaper than other catalytic methods that have been explored/invented to depolymerize PET into TPA monomers. These qualitative cost estimates are based on the reaction conditions (temperature, solvent, other reactants (in this case, humid air)) and the unit operations involved in the downstream separation processes that isolate the TPA product from unreacted PET. The largest hurdle that precludes widespread deployment of technologies for PET recycling, as well as those for most other plastics, occurs (way) upstream of the reaction and separation train. The highest cost is related to collecting and sorting used PET bottles and TPA-derived textiles.

Mechanical recycling or any flavor of chemical recycling (pyrolysis, hydrolysis, etc.) all suffer from the same hurdle. If the target product of the recycling process is a TPA-derived plastic (be it for clothing or soda bottles), then mechanical recycling is usually cheaper, since it produces a product that only needs to be reshaped and remolded to give shirts or jugs. Chemical recycling converts PET into its constitutive monomers, and to (re)produce a TPA-derived plastic from the monomers requires a not inexpensive (re)polymerization step, in addition to reshaping and remolding.

Chemists, even highly regarded ones like Tobin Marks, are less interested in "solving" the PET recycling issue and more interested in the fundamental chemistry involved in chemical recycling. Issues of Green Chemistry (or blurbs in phys.org) are not the appropriate reading materials to get insight into costs, scale-up, etc.. Very few, if any, academic journals are focused on such matters, and rightly so, in my opinion.

Yeah, these are pizza oven temperatures. The temperature appears to be just above the melting point for PET. It is also in the liquid phase for PBT, PEN and PEF.

I think most recycling methods for PET require melting anyway.

4 hours sounds like a lot of factory space to generate a substantial flow of output.

> Finding it also odd that biodegradable plastics and safer alternatives are going quiet.

They tend not to be a good solution to anything.

There are a couple of ways of making degradable plastic. One is to add something to their manufacture so they break down into shorter chains which their supporters tell you will then further break down. These are generally referred to as OXO degradable.

Another is to use bio based plastics such as PLA or cellulose. These both have poor performance compares to oil based plastics.

All of these also require industrial composting where they add no nutrition to the compost, effectively just bulking it out. They [generally] do not break down when littered or even placed in a domestic compost heap.

There is also a problem because these plastics are virtually impossible to sort from recyclable plastics so if they get in each other waste stream the whole batch can be rendered contaminated and useless.

Incalculable mountains aren't a real environmental problem. People just believe that for some reason. We can just leave them there forever. The actual environmental value in recycling is reducing the CO2 emissions from making new plastic by reducing production of new plastic. I don't know if biodegradable plastic actually helps at all or just placates the people worried about the fake problem of incalculable mountains.

Biodegradable plastics suffer from either being hard to degraded or hard to use without degrading. It's a difficult conundrum

Short answer: yes.

All industrial processes recycle heat extensively. Heck even distillation based desalination isn't that inefficient because you do in fact recover the heat.

Well let's truly hope that its not that much expensive