The Misleading Biodegradability of PLA

Biodegradable PLA

 

The vast majority of FDM (fused deposition modeling) 3D printers primarily consume ABS or PLA filament. ABS, a petroleum based thermoplastic, is a little tougher and bit more flexible than PLA, but also a little more finicky to print with. ABS generally requires a heated bed to reduce warpage, and also emits a potentially troublesome scent as it is extruded. PLA on the other hand, or poly lactic acid, is derived from starchy sources - most often sugarcane or corn starch and has a far more palatable (some note a breakfast waffle-like) scent when extruded.

The marketing writes itself. PLA is a natural, bio based alternative to petroleum laden ABS!  Sounds (and smells) like you could eat it! I'm a hands on guy so I tried a nib, tastes like plastic. The baked out, boiled down, unsweetened truth is that it is indeed, plastic. Marketeers love to tout the biodegradability of the material, and its true, that at some point it will biodegrade. The reality however, is that this process will take several hundred years in a typical landfill. To biodegrade, PLA requires a laundry list of conditions to effectively break down. Specifically - oxygen, a temperature of 140+ degrees, and a 2/3 cocktail of organic substrate. Collectively, these are absent in any scenario outside of industrial composting facilities. This means that PLA plastic will sit in that landfill right alongside ABS and other plastics for a very long time.

When considering the environmental friendliness of a particular product, it is essential to consider the amount of energy used to create that product. For all plastics, the energy required is particularly significant. This dictates that the ultimate waste of that energy is to literally discard it. For this reason, keeping the material in its intended physical form is far more responsible. 

What do we propose? Print responsibly and recycle accordingly. The Filabot, for lack of a better engineered example, is capable of turning your old PLA or ABS prints into fresh filament again so you can indefinitely extend the practical life of the material. Plastic, once it has been industrially produced, is categorically best staying plastic. Giving this plastic renewed purpose is the key, and is ultimately a far more productive future than an impractically slow death in the ground. 

 

 

 


9 comments

  • Karel Lootens

    So the message to all your readers should rather be – dispose of your PLA in the compost bin, so it gets industrially composted and becomes a fully eco-friendly alternative to ABS, no?

    It shouldn’t land on a landfill – it should end in the compost facility.

  • Jim

    > The EU standard EN 13432 mandates: Disintegration [..] composted with biowaste for
    3 months. After this time, the mass [..]

    What is this a mandate for? For being able to say something is “compost-able”, rather than “recyclable”? Surely it wouldn’t mean that you couldn’t say (presumably in fewer words), “is recyclable into biomatter in a proper waste processing facility that uses appropriate shredding technology, pre-treatment, filtering, and long-duration microbial bio-processing”

  • iksea

    I have investigated PLA compostability for work projects in the past and dug into understanding what BPI and Cedar Grove (PNW compost facility) are looking for to certify a polymer or fiber based product to be compostable. The reality is that you may want your PLA 3D prints to compost, but they will not in the commercial facilities because they have too thick of wall sections to degrade in the batch time of the process. Most systems use 12 weeks or so to break down and if the wall sections are too thick, this will not happen. This is what made it hard to come up with compostable forks/spoons initially since you need some thicker sections for strength. Because most 3D prints are much larger/thicker than utensil wall thicknesses, they most likely will not compost in the time allowed and will be screened out with the rest of the contaminates and sent to the landfill. The only way to ensure that composting could happen would be to shred your parts into fine shavings (<.06") before sending to the compost. Another issue would be that the colors and additives are most likely not food safe and would most likely contribute to chemical contamination unless specifically formulated for this purpose. Look up PFAS and BPA chemical contamination of compost from migration from treated paper products. Another toxic mess building up.

    The EU standard EN 13432 mandates:
    Disintegration, namely fragmentation and loss of visibility in the final
    compost – this is measured in a pilot composting test (EN 14045) in
    which specimens of the test material are composted with biowaste for
    3 months. After this time, the mass of test material residues has to
    amount to less than 10% of the original mass.

    https://docs.european-bioplastics.org/publications/bp/EUBP_BP_En_13432.pdf

  • Adam

    PLA can be composted in commercial composting facilities. It is a much more renewable plastic for 3D printing than ABS.

  • Me

    Compare hundreds of years for decomposition of PLA to effectively “never” for ABS. True, PLA may take a while, but it’s still a vast improvement over ABS. And less toxic than ABS if ingested by marine organisms. It’s not perfect, but it’s a step in the right direction.

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