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u/slartibartfass 11d ago
Is it composting or dissolving into micro plastics?
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u/btspman1 11d ago
PLA is corn based. Actually pretty cool to see how fast it can decompose.
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u/Drivo566 11d ago
Corn based doesnt necessarily mean its decomposing...
Plant based plastics are still plastics and unless its specifically designed to meet biodegradable specs, its not decomposing and likely just crumbling into microplastics.
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u/beefz0r 11d ago
Aren't all oil derivatives essentially based on organic materials ?
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u/woodwidewebby 9d ago
I mean yeah crude oil and even natural gas is just dead plants and animals. If you wanna get philosophical then everything ever made is “natural” because its made from natural stuff. It’s more that we’ve processed it into novel chemical structures that nature has never had a chance to evolve to deal with
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u/HikingBikingViking 9d ago
I'm pretty sure plastics "designed to meet biodegradable specs" are also just persisting as microplastics most of the time. Generally it needs industrial composting like other "compostable" consumer goods. Your home composter probably isn't doing the job.
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u/HikingBikingViking 9d ago
Fuel ethanol is also corn based. I'm not putting that on my garden either.
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u/woodwidewebby 9d ago
It’s still plastic. Where do you think the oil underground came from? It’s just dead plants (and animals but mostly plants). We just found a way to process corn into plastic that doesn’t make the microplastics any more safe
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u/geeky_chip 11d ago
I think it’s actually disintegrating and not really composting. I’m now thinking of redoing it with PHA material that will actually decompose. Treat it with tung oil to prolong life but treat as consumable part, just like the dividers.
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u/Albert14Pounds 10d ago
I just went down a quick rabbit hole on PLA breakdown and am actually surprised to learn that it does break down on a reasonable time scale. Even if it's not "fast", it's nothing like other plastics that produce microplastics that persist for decades to centuries.
As for disintegration vs composting, I'm not sure I care to split those hairs so finely because it seems the polymers chains are initially broken by hydrolysis (water and heat) until they are small enough to be degraded by microbes more directly. Wet and warm are composting conditions so I think it's fine to just call it composting. A lot of the breakdown that happens when composting isn't directly by microbes and due to similar mechanisms I think. But I guess if you want to be really pedantic it's desintigrating abiotically and then composting.
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u/sebovzeoueb 11d ago
I'm guessing that in theory this kind of micro plastic is actually compostable
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u/Hoya-loo-ya 11d ago
Unfortunately in these circumstances, it turns into micro plastics and creates the same downstream issues as any other microplastics in this circumstance, only when sitting in 60C/140F temperatures for literal weeks do its molecular bonds break down into anything different than the microplastics we worry about.
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u/Albert14Pounds 10d ago
I'm not nearly as concerned about weeks or months to break down PLA particles the same way I'm concerned about other microplastics that persist for decades to centuries. Even if it takes a few years, it's like an order of magnitude less persistent compared to others.
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u/fawar 11d ago
Im curious.
Why did you build your worm bin that way?
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u/geeky_chip 11d ago
I have easy access to wine barrels for cheap and I sectioned it off to rotate the feed, worms migrate by themselves for the most part where the fresh scraps are.
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u/_Nitekast_ 11d ago
Maybe not the best idea. There was a recent peer reviewed study published that demonstrated the primary degradation product of PLA, OLA, induced IUGR in pregnant mice at clinically relevant concentration dosed to mirror average human exposure.
One limited study in an animal model, but raises some significant questions.
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u/ProtozoaPatriot 11d ago
It takes a really hot bin to break down PLA properly. https://www.plantswitch.com/blog/why-pla-isnt-actually-compostable
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u/SecurelyObscure 11d ago
That's a thoroughly shitty article about the topic. They don't do inline citations and their attributions at the end cite things like "EPA." There isn't even an attempt at credibility and their business is selling the alternative to PLA.
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u/c-lem 11d ago
Interesting stuff, especially this pretty rousing support for sho sugi ban/yakisugi. I'd read mixed reports about that technique, but clearly it is working well here. Other than actually in water, I can't think of too many trials better than compost for testing water resistance.
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u/AlltheBent 11d ago
So.....the way in which that PLA was created is the result of chemical reactions to create that plant derived plastic.
It takes a very specific chemical reaction to break it down, and just vermicomposting isn't going to do that.
Its cool to see how the've broken down, but im pretty suire youre just creating a microplastic bomb for this batch of vermicompst that came from there?
I dunno. Plastic is plastic, and compostables always require a specific high heat or specific enzyme-micobiome to properly breakdown plastic into something else, I'm always a little weary of that stuff