How to Compost Biodegradable Plastic
Question
March 9, 2025
I 3D print lots of PLA (Polylactic Acid), a compostable organic polymer, but have so far found no practical way to compost my PLA waste. "For PLA to compost properly, it needs to reach hydrolysis conditions to break the long plastic chains into shorter units microbes can digest, which means getting it heated to the glass point (around 55C) in the presence of water for an extended time." I don't imagine you have a solution for this, but others printing PLA out there might constitute enough demand to warrant a solution. Have you had any other inquiries on this?
Answer(s)
Answer by JH: Interesting question. What I’m reading about PLA composting is that the process you describe must be precise in order to completely break down the PLA fragments and that even an industrial composting operation may fail to fully decompose the fragments which would then end up in the soil. For this reason it doesn’t appear to be within our mission of teaching backyard composting to address PLA composting.
Fortunately there are numerous resources online about PLA composting for someone wanting to do so. And there is evidently a new type of PLA that is more readily compostable being a combination of PLA and thermoplastic starch. Read more about this at
Answer by JZ: In addition to what JH has sent you: Decomposition of any organic material is dependent on the action of microbial enzymes on the substrate in the presence of air, moisture and time. Just a thought, you might do your own experiment with heavy-duty inoculation. For example, use separate compost bin. Add 4” or more of moistened finished compost to the bottom, then "sprinkle" some pieces of the polymer to the top, then cover that with another 4" of moisturized compost. Maintain 50% moisture in the bin in all seasons. Then keep a record of how this process evolves in the bin over time. I think that you will need to be quite patient for a result. This would be a cold/static composting process. If you choose to due a hot process setup, then you would follow the hot process guidelines. Does that help?