The global issue of plastic waste has prompted scientists to seek innovative solutions for recycling. Single-use plastics, notorious for their environmental impact, require new methods for efficient and sustainable management. For some common plastics, though, salvation could be at hand, with researchers identifying a common enzyme that can be used to break them down fast.
Researchers at King’s College London have discovered an enzyme used in laundry detergents that can break down PLA plastics within 24 hours, using a little heat as an aid. Normally, this is achieved via composting methods that take weeks or months. This method transforms the plastics back into their original chemical components, offering a rapid and eco-friendly recycling process. The monomers can then be reused for manufacturing new plastic items.
One wonders if this could also be used in another way – perhaps in a multimaterial printer, allowing PLA to be used for supports and then broken down. It’s probably not that necessary, given other degradable materials exist, but it’s something to think about.
This project is a significant leap forward in recycling technology, showcasing the potential for enzymes to revolutionize how we handle plastic waste. It could also be a great way to recycle all those errant deformed Pikachus that keep ending up in your hackerspace’s 3D-printing waste basket. In any case, plastic waste is a problem the world needs to solve, and quickly, because it’s not going anywhere any time soon. Video after the break.
Using PLA as support for a different material works pretty well even if it’s not soluble, PETG for example doesn’t really stick to it, so if you have a dual nozzle it’s worth doing.
I suppose the question will always be the economics of it. They heated it to 90C and used what looks like a very expensive ionic liquid. Hopefully they’ll find a more cost efficient way to do it.
“Mutant 59 The Plastic Eater
Book by Gerry Davis and Kit Pedler
90C wasn’t the conditions I was hoping for for PLA recycling. But utilizing lypase at 90C is its own achievement. Previous attempts are limited to 55C and take many days.
Hmm… maybe they’ll work out a way we can use Fairy non-bio to dissolve failed PLA prints.
:o>
Non-bio is the stuff without the added enzymes
“And so we’ve actually chosen PLA, a class of plastic which is very difficult to recycle with current technologies. This is the plastic that is often found in coffee cups, or cups you get in beer gardens, straws, packaging for food.”
Apparently paper cups with PLA coating are a thing (oddly enough also for hot beverages), but most of the stock footage they use looks a lot like PE. In turn, PLA isn’t what I’d call “difficult to recycle” when you can literally bury it in an industrial compost pile and sit it out. Try that with PE/PP or polyimide. Funny enough, even Bakelite has become bio-degradable in a sense (https://doi.org/10.1021/es060408h).
They key benefit here is that one can turn impregnated paper cups into ionic liquid contaminated paper cups :) So at least the pure, washed PLA packaging is fair game for recycling, which is cool in its own right, albeit somewhat oversold in the video.
Burying it in the ground very specifically isn’t recycling.
It is if you plant corn in the ground and make more PLA from it.
If you could use PLA as a “fertilizer” it certainly would be.
Everything is recycling, maybe just not a human scale.
Exactly
I was going to point out how wasted heat energy, radiated out into space, isn’t recyclable, but, possibly, on the time scale of more than one universe, perhaps it is.
I think the key here is that unlike other methods it actually turns the pla back into it’s original ingredients which in turn can be used to remake more pla of the same quality as the original product. If you recycle pla by melting it down to make new products, it becomes weaker each time. This method doesn’t have those limitations. Now instead of composting it to get rid of it, you can reuse it instead of using up more natural resources.
I totally see your point about it being one of the plastics that is already easier to deal with though. But, I still think it’s a huge step.
I recycle my PLA scrap and convert it back to precursor molecules in a much simpler way: I put it in the woodstove as fuel. It burns very cleanly, with no ash. Just water vapor and CO2 is produced — no fumes, no particulates. Much cleaner than the wood fuel it displaces.
This is not cleaner than wood fuel…it still produces CO2 ( and probably other pollutants). Quantity doesn’t matter.
Better stop exhaling then. You produce a half ton of CO2 per year.
PLA (and PE) are essentially perfect solid fuels. No ash, no soot, no particulates, no smell, no creosote. Much better than wood. And when burned correctly, no hydrocarbons, no nitrogen oxides. Just water and CO2. Food for trees. Perfect recycling.
There is overwhelming evidence that burning plastics creates dioxins and other toxic chemicals. That is the crucial problem with trying to turn plastics into fuel by pyrolysis. None of the companies that have built plants for this method, and want to build more, have been able to solve the problem. That is why there is strong resistance to this technology.
There are many harmful chemicals in plastics beyond the hydrocarbons. Burning and pyrolysis does not destroy them, they just release them to the environment. You are doing harm by burning plastic in your wood stove.
There is no good way to deal with the plastic that is collected for recycling. Much of it is sent to landfills. Much more of it is burned in cement kilns, but that might become illegal when enough of us realize that burning and pyrolysis of plastics to get rid of it is a big mistake.
PLA is a particular “plastic”, not plastic in general. What may apply to many constituents of the class, may not apply to the particular member. Your argument would be a lot more convincing if you would stick to the topic, i.e. PLA, and provided some data to support your contention.
This is outdated knowledge. Look up the Amager Bakke incineration plant, we can scrub dioxins now.
The Persistent Organic Pollutants popularly lumped in as ‘dioxins’ are those with halogens (e.g. chlorine, fluorine, bromine…) in the chemical makeup: that’s what makes them persistent and pollutant. There are no halogens in PLA or PE.
Many other plastics (PVC, PTFE…) DO contain halogens and have the potential to create POPs. Don’t burn those.
Other plastics like polystyrene and ABS also don’t contain halogens, but are less easy to burn completely outside of a dedicated incinerator, so can produce carbon monoxide, soot and other incomplete combustion products. Don’t burn those either.
Burning wood creates dioxins.
Especially when burned rich and cool. Like a campfire.
Those produced by hickory wood are particularly tasty.
But doesn’t fit the narrative.
“Dioxins” comprise a large family of compounds, only a few of which (basically the halogenated ones) are persistent in the environment and considered “bad”. The dioxins produced by burning wood aren’t on that list. Still, don’t huff them on purpose.
When you burn PE you put fossil carbon into the air. No different than burning coal. Burning PLA puts last years carbon back into the air. No net increase in CO2
If we’re going by greenhouse gas, composting produces as much CO2 along with methane. Unlikely that any recycling process will fail to produce Co2 since the polymer is a product of reduction.
Came here to post this. Waste plastic is infinitely more useful as fuel than as a low-grade feedstock to make new plastic worse. Reverse logistics will never be practical and recycling is a feel-good scam. Just give up and burn it, and be done with it.
Valid point – but there’s a subtle difference here. Depending on the manufacturing process and the origin of the origin of the original feedstock used to make said pla, burning it can and should have a far smaller overall environmental footprint than doing the same with a polymer derived from a petroleum feedstock.
PLA and PE will both, technically, burn and produce the same combustion products that can be reabsorbed by the atmosphere. However, the carbon in the PLA came from this current atmosphere/climate system, whereas that from the PE did not.
True, but the fundamental issue of atmospheric pollution is the human population, not the particular technology we use. With few enough people, anything we burn will just get absorbed by the environment and turned into biomass. If we’re exceeding that limit, tweaking our tech to make adjustments is really just kicking the can down the road. See also: the Jevons paradox.
What if we’re burning the population for fuel?
You first.
Fire is kind of small, start with feet.
@HaHa
Never understood why people get personally offended at the idea that maybe infinite growth is bad. Like I didn’t shoot your dog, man. Calm down.
Never understood why people who advocate for fewer people don’t lead by example.
‘Infinite growth’ is an old, often derped, commie strawman. Do better. Do you really want to be associated with ‘those chanting morons’?
First time I’ve heard “reverse logistics” to describe this. It’s a good phrase. Oh and ignore the trolls downthread who pretend they can’t tell the difference between population strategy and genocide :-)
It doesn’t seem to burn easily. Do you shred it and/or mix it with wood?
Both PLA and PE melt at low temps and behave like melted candle wax or lamp oil. If you’re just burning in a plain woodstove it does need something to wick it, and a decent heat and flame already to melt it and ignite it. Cardboard works, as does other kindling, logs, or coals. Cinder and ash will too, but the stove needs to be hot for that. Once melted and lit, the energy content is high, and it burns hot and clean. Thin pieces like filament ends and brim offcuts I just throw in with the paper & kindling at the start of a burn.
The trouble is, most waste plastic in need of recycling is NOT PLA. Bottles, bags, hard clear packaging… none of these are PLA. And PLA in need of recycling can just be melted and then cast in to printing reels, industrial scale printing pellets, or finished objects. All this enzyme does is threaten to disssolve 3d printed items if it ever gets integrated in to the DNA of some geneticlly modified microbe which then goes rogue in a “grey goo” scenario, albeit one which only grey goo’s PLA objects.
Heat the enzyme and your collection of 3D prints remain safe. And don’t let a bacteria form a biofilm over your stuff, a little bit of dish soap puts a stop to that quickly.
Long term, we’ll probably throw all that other mixed plastic crap into a steam cracker and make syngas or just straight pyrolysis of waste plastic in an industrial incinerator. Probably only thing for the extremely dirty plastic we find in the ocean, it’s shedding microplastic so badly at that point that doing much other than stuffing it into a steam chamber or incinerator is asking for trouble.
Headline from 2065: “Bioplastics leading cause of microplastics in environment”.
Lets not kid ourselves, plastic is plastic. It’s used in 99% of all products made today. The only way we can safely reduce the amount of plastic in the environment, IS TO NOT USE IT.
That will never happen though…so enjoy all the health and ecological disasters until you die from plastic related health complications.
“Plastic is plastic”. By that logic, “bacteria are bacteria” and all hazardous to human health, so we must all live in a glass bell jar to keep them out, after we have laboriously removed them from our digestive tract. Water is water, so any water you see, you will be able to drink, so pee into a glass, because it’s water.
We live in a world where, if we have access to the comment section on Hackaday, we likely have access to a considerable portion of the knowledge laboriously collected by human beings over the last 4 or 5 millennia. There are even sites that condense what’s out there into nifty bite-size pieces to summarize it into something a 12 year old can learn. There is certainly enough information out there to help you understand what “plastics” are and why we bother to use them at all. For example reducing transport weight of food being shipped (reducing fuel consumption), increasing the time before food spoils (reducing fuel and fertilizer consumption, making more food available for the 8 billion people on the planet reducing starvation and improving nutrition for even the poorest people). I could write more, but the info is already out there, ready for you to educate yourself.
He’s kind of right, though. Sure you could take the big-brain nuanced approach and talk about all the different types of thermoplastic resins and their various properties and why they’re not *all* bad. But then five seconds later someone’s going to figure out how to make some cheap and indestructible fluoropolymer and we’ll all be making clothes out of it and choking the whales. Never underestimate the destructive power of good intentions. Also, if we need to optimize our food production so hard that people will starve if we put milk in glass bottles, maybe we should consider cutting back on reproduction for a generation or two. Just saying.
Not really. What differentiates “plastic” from many of the biologically produced polymers that are already out there?
You know, like lignin on trees? Oh dear, there’s particles of wood in my drinking water! Says nobody.
>What differentiates “plastic” from many of the biologically produced polymers that are already out there?
Millions of years of evolution adapting us to those polymers.
No plastic? So back to whale bone and ivory?
Or better materials, like metal, wood, or glass.
Whale taste better than crude oil
Problem with today is not that we do not have solutions like these. I am friends with a nan that has a plant that turns plastic back into oil/fuel. Its an amazing system that continuously can be fed plastic and once heated the methane released is used to continue to maintain the required heat. A true solution. Yet.. those in government leadership positions do not want solutions like this and the one in article. Contracts of particular parties paid to take plastic and incinerate it has a controlling say where plastic waste goes. Thus greed and corruption is the problem, not plastic.. and our governments seem too ignorant or weak to change this.
What about the plastic used to clean dirty dishes that slowly breaks as we use them?
It’s gratifying to see people figuring out how to recover monomers rather than grinding and re-melting ad nauseam. There was another project that figured out how to do it with cyanoacrylates (which is already done in the production of super glue, these guys mainly figured out how to give the polymer better material properties to try and compete with materials like polystyrene). ( https://www.science.org/doi/10.1126/sciadv.adg2295 )
Well, that’s great!
But I wish some effort was going into ways to break down or recycle other filament types. In particular, ones which do not go to mush in a hot car. Or maybe ones where the filament on the spool doesn’t turn brittle like uncooked spaghetti if you keep it too long before printing.
PLA kind of sucks!
That’ll be the next steps. I think PLA is perfect target since it’s popular for 3D printing. Maybe nylon should be next, it’s common in manufacturing already and slowly coming to 3D printing. Or PET used in pop bottles, it is notoriously difficult recycling.
I’d be very interested in this for making molds. Right now, I’m having some trouble with using PVB and trying to burn it out. If I can dissolve PLA, it might be cheaper to make molds and means I don’t have problems. With burning it out.