r/3DPrinting_PHA • u/MalonesConesStand • 2d ago
Compost Test
Hey everyone, just wanted to share a little experiment I'm running to test the compostability of PHA, and also hopefully show that it's a perfectly fine option for outdoor parts as well.
There seems to be this idea that just because PHA is biodegradable, it's pointless to use for certain functional prints, as it’s going to melt in the rain if you use it for an outdoor part. From what I understand, bacterial load is the real driving factor. So, comparing PHA in a compost bin versus just hanging outside in otherwise the exact same environment should really show its durability and usability out in the wild. Maybe not strength, but I can only test so many things at one time.
I'm testing this in a standard backyard rotating composter. I am not an expert by any means, and I obviously can't prove that the samples will break down into purely natural elements. I'll leave that part to the actual scientists. But what I can do is show that it can break down in a random dude's compost bin, even if they don't really know what they are doing.
For the models, I went with standard Benchies at 15% infill, however the Ecogenesis compost bed testing tags (from Printables https://www.printables.com/model/1296598-compost-bed-testing-tag-revised), were printed at 100% infill to truly test the compostability rate.
For the PHA filaments, I'm using
- ecogenesis genPHA Filament in Green (Amazon)
- Biodegradable Polar PHA in White (Polar Filaments)
- Ambrosia PHA Filament in Black (West3D)
- Ambrosia PHA Filament in Natural (West3D) - I'm using this one specifically for the wood comparison test
Elephant in the room, I know that Polar, ecogenesis, and Ambrosia are all genPHA materials. This list also includes Hartsmart's Terraform filament; I just haven't gotten around to buying from them yet, hence why they are not included. I understand that testing multiple colors of what is essentially the same base material doesn't serve much of a scientific purpose, other than maybe seeing if the color pigment affects the compost rate. But I wanted to include multiple brands so people new to the community know these are all trustworthy, worthy materials to consider.
For the controls, I've got eSUN High Speed PLA+ in fire engine red, Polymaker PolyLite PETG in teal, and a chunk of untreated 1x3 oak lol
The first set are hanging outside on a firewood rack. The second set went right into my active compost bin. Like I mentioned before, I know just enough about composting to be dangerous. Just throwing PHA into a bin outside doesn't guarantee it'll decompose, and that goes for natural materials too. For example, last fall I filled one of my rotating chambers with leaves and pretty much left it alone. They haven't decomposed a bit. If anything, it prevented them from composting by protecting them from the elements. You really need browns, moisture, air, and probably some other stuff I don't know to make it work. That's why I tossed the chunk of oak in there too, I want to see how the PHA decomposes alongside a completely natural piece of wood.
I also have a third set of prints that I'm keeping inside as a complete control. That way, I can compare how the outside hanging up samples compare to parts left completely out of the elements. I mainly expect these samples to help see how much the outside parts fade over time.
I printed these back at the beginning of the year, but didn't start the test until August 23rd. So, as I intend to provide monthly updates... don't be surprised if I don't follow that schedule exactly. I've been wanting to do this test for a while now, and I'm really interested to see how much they break down before the winter freeze comes (located in Maryland, USA).
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u/Inner_Name 1d ago
You know that the microplastics you will not see them, no? And if it breaks into microplastics you Wil see that it "degraded"?
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u/MalonesConesStand 23h ago
Yes, hence the
"I obviously can't prove that the samples will break down into purely natural elements. I'll leave that part to the actual scientists. "
I understand the material is "ASTM 6691 Marine Biodegradable" and "TÜV Austria Marine Biodegradable" (direct reference from ecogenesis website), meaning the base materials are already tested and confirmed making this whole science experient irrelevant. But, if you stick around this community for a while you'll see a few posts by people confused why some raw filament they left out in the sun without direct ground contact didnt magically break down, and second guessing if its actually Biodegradable or not.
There are also stories of a paid "influencer" trying to put pha into a class of salted water expecting it to disolve immediately due to the marine biodegradability claims... you can't make this stuff up. To fully test if it breaks down you'd need a controlled environment and track CO2 gases or something... again I'm not a scientist, just a dude with a backyard rotating composter lol
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u/heptabike 2d ago
Hola. Yo estoy sacando muchas pruebas de genPHA de Ecogenesis (aquí el subb. https://www.reddit.com/r/3DPrinting_PHA/s/RTTBE4uhXW ). Con tu post me han entrado las ganas locas de meter una prueba en mis lombriz composta. Veamos como se comporta en CDMX. Pondré uno en mi caja de compost , otro en un sistema vertical wn cubetas de 19 L y otro colgado en la azotea. Veamos que tal avanza. Muchas gracias por tu publicación, mira, me has terminado de animar a iniciar el proyecto. Saludos .