Scientists break down plastic using a simple, inexpensive catalyst and air
56 comments
·March 21, 2025piokoch
dwighttk
There are actual reasons different plastics are used in different situations… it’s not just companies saying “ha ha this will be extremely difficult on the recyclers!”
Some plastic needs to be heat resistant, some, it doesn’t matter. Some plastic needs to be easy to tear, some needs to resist tearing. Some plastic needs to be flexible, some needs to be stiff.
Easily removable labels often fall off before they are actively removed.
Restaurants probably tried only paper and their customers complained when the food soaked through and/or the container collapsed.
asah
Dumb q: could one stay the catalyst on everything, let the PET break down, then separate from the other polymers?
mbreese
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.
bschwindHN
Very good questions, but the answer is disappointing:
because money
mc32
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.
nervousvarun
That's an important point you're making here...Can you expand on that with an example? A specific use of plastic as a container that gives the desired characteristics...specifically where those characteristics could not be met by another (if expense isn't a consideration) material?
If there are less toxic materials that could "do the job" but are more expensive then it really is about money no?
lxmorj
Wouldn't (fully) burning all single-use plastics effectively make them no more long-lived and problematic than burning crude oil at sea? I know that's a low bar, but it seems like at least you're getting two uses out of them at that point...
Mashimo
And if you produce heat / energy from burning it, you can technically call it recycling :)
Put some filters on top of the power plant exhausts and it's clean enough to build a ski slope on top of it.
Synaesthesia
A lot of plastics are incinerated. I think it has to be at a high temperature. Of course this does emit carbon dioxide.
culi
What percentage is actually broken down into monomers? How much microplastic waste is left behind. Given the reliance on "ambient air" I imagine it's not 100%.
Regardless, I'm excited to hear about progress on solving the plastic waste crisis. It seems better than the current alternatives the article presents:
> "The U.S. is the number one plastic polluter per capita, and we only recycle 5% of those plastics," said Northwestern's Yosi Kratish, the study's co-corresponding author. "There is a dire need for better technologies that can process different types of plastic waste. Most of the technologies that we have today melt down plastic bottles and downcycle them into lower-quality products.
ac29
> What percentage is actually broken down into monomers?
"In just four hours, 94% of the possible TPA was recovered."
stosssik
A promising approach—especially if it proves as simple and low-cost at scale. It’s obviously not going to "disrupt" the plastics industry overnight, but it could offer a valuable local alternative, particularly in regions dealing with massive plastic waste imports. The real question is whether this kind of tech can evolve outside of patent lock-in and centralized exploitation models.
Synaesthesia
This is a realm where government regulations can really make a big difference. China banned single-use plastics. A lot of plastic use is really unnecessary.
thrance
And Trump reverted the ban on plastic straws. One step forward, three steps backwards...
culi
This is great but PET (symbol #1) is one of the few plastics that ARE recyclable. I wonder if any of these techniques can be used to solve the non-recyclable plastic problems
math
Aduro’s tech works with hard to recycle, dirty, mixed plastic. Search for Eric Appelman interview on YouTube for more info. Some of the retail investor coverage is cringeworthy, but my take is the tech is likely as good as described (disclosure: I’m an investor).
aitchnyu
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?
math
Results will vary a lot with all the parameters (of which there are many). They don’t disclose all the detail but I know they have done thousands of tests across the parameters space. I know they believe they can process sludge produced from other processes.. The industry generally is very opaque, I think for competitive reasons and also because it’s so complex/nuanced.
iwontberude
Not infinitely so, maybe this is used on old PET
voidUpdate
This is cool! Can't wait to never hear about it again
wolfi1
there is also the possibility to recycle pet-bottles into food grade bottles again using just mechanical means, I know at least two European companies who provide such machines
PaulHoule
I've seen 100% recycled PET bottles for Coca-Cola products in the US
https://www.cnn.com/2024/03/19/food/coca-cola-new-bottles/in...
and Pepsi is selling 100% post-consumer bottles in some EU countries
https://www.pepsico.com/our-stories/press-release/pepsico-co...
Those clear beverage containers are an ideal case for mechanical recycling. This company
makes polyester fiber from recycled PET. I have a few garmets made from it and my impression is that the fabric feel is nicer than average.
culi
Yes PET (#1) and HDPE (#2) are the two easiest plastics to recycle and the most commonly recycled
culopatin
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
null
kikokikokiko
Well, they used a "simple, inexpensive catalyst" and then HEATED the plastic/catalyst mysture. Nowhere in the article it gives you an estimate of the final cost of the process.
kibibu
The journal article is open access. https://pubs.rsc.org/en/content/articlelanding/2025/gc/d4gc0...
> Catalytic amounts of AC/MoO2 selectively convert waste PET into its monomer, terephthalic acid (TPA), within 4 h at 265 °C with yields as high as 94% under 1 atm air.
I'm not a chemist so don't know if you can find a way to calculate the cost, but the authors claim that it's cheaper than current methods.
The bigger deal imo is that it recovers PET monomers from mixed plastics, which means avoiding manufacturing more plastic.
PaulHoule
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)
culi
> about 50 cents a pound which makes it hard for any kind of recycling process to be competitive.
We've had almost a century of subsidization of the oil industry. The gov't needs to play a bigger similar role if the recycling industry is ever gonna be able to compete
We need a tax on the full lifecycle cost of plastics so we can stop treating waste as an economic externality
jandrese
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.
roughly
In fairness, that’s mostly because current plastic production externalizes the cost of everything about the lifecycle before and after manufacturing and use.
alhw
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.
projektfu
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.
baranul
Keep seeing these "possible breakthroughs" in breaking down plastic waste, but no concrete time frames on expanding to scale nor real world costs. Meanwhile, the mountains of plastic continues.
Finding it also odd that biodegradable plastics and safer alternatives are going quiet. As if the new scheme is to keep fossil fuel companies rolling, with the promise that one day a solution to get rid of incalculable mountains of plastic will be found. Don't worry, feel free to plastic pollute, because one day there will be a solution.
m463
I wonder if processes like this can recycle the heat?
Kind of like fresh air exchange into a heated house where new air in gets heated exchanging with old air out
IAmBroom
Yes. I can break down plastics that way, using ordinary tap water.
Actually, the tap water is optional.
And instead of monomers, the end product is carbon - which is even more recyclable!
kylehotchkiss
I was expecting a much more complicated catalyst!
whynotnowplz
Why don't we throw all our trash into a volcano?
gsf_emergency_2
Because historically, volcanos are thought to prefer high value offerings like live human beings
dinkblam
or golden rings of power
01HNNWZ0MV43FF
It's expensive to get the trucks there. Some toxic landfills like Florida don't even have any volcanoes: https://osm4wiki.toolforge.org/cgi-bin/wiki/wiki-osm.pl?proj...
There is no such a thing like "plastic". The article is about PET - polyethylene terephthalate, there are hundreds other "plastics", which different chemical propensities. The problem is not actual act of recycling, but figuring out what a given piece is made of. PET is popular - 70% of all bottles are made of it, but there are those 30%, so the most expensive part - sorting - has to be carried anyway. Plus we target only bottles.
Recycling is a great example of the rule "Privatizing Profits and Socializing Losses". Business is packing their stuff in whatever they want and then citizens, authorities has to deal with the wastes business produced.
Why we can't force to use for bottles/packaging a single type of plastic? Why we can't force easily removable labels on the bottles (the glue that is used to stick half plastic/half paper labels is a deal breaker for simple recycling), I think only in Japan this is mandatory. Why we allow making packages (especially for take-away food from pseudo-paper (which is a paper with plastic coating), which is not recyclable at all and, in fact, is much worst than plastic, but business claims that "now we are eco, see, we use paper for packaging)?
Why we allow to use for packaging whatever business wants? Why the cost and effort of the recycling has to be on people and local governments?