9

So they say PLA is biodegradable. But I still don't know how much biodegradable.

I live in a flat and we have composting trash can in the courtyard. However if I throw PLA in there and it does not decompose, neighbors are gonna be pissed since many of them are intending to use the soil for their balcony flowers.

So can I really compost PLA, or does "biodegradable" just mean it falls apart eventually, eg. in years? And if it decomposes, is it safe to use for plants?

Tomáš Zato
  • 512
  • 6
  • 22

3 Answers3

7

This question has been asked on just about every forum out there. Here's one example from filabot.com .

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 [Fahrenheit -- ed note], and a 2/3 cocktail of organic substrate. Collectively, these are absent in any scenario outside of industrial composting facilities.

I found similar comments -- tho' with perhaps slightly lower temperatures elsewhere.

Trish
  • 20,169
  • 10
  • 43
  • 92
Carl Witthoft
  • 3,008
  • 1
  • 9
  • 15
2

TL;DR - No... well, yes you can, but it won't decompose in your lifetime.

Addressing this question fully - from the point of composting, rather than landfill:

  • From Wikipedia - PLA - End of life:

    Composting: PLA is biodegradable under industrial composting conditions, starting with chemical hydrolysis process, followed by microbial digestion, to ultimately degrade the PLA. Under industrial composting conditions (58 °C), PLA can partly (about half) decompose into water and carbon dioxide in 60 days, after which the remainder decomposes much more slowly, with the rate depending on the material's degree of crystallinity. Environments without the necessary conditions will see very slow decomposition akin to that of non-bioplastics, not fully decomposing for hundreds or thousands of years.

  • According to Is PLA filament actually biodegradable?:

    It takes 80 years to biodegrade naturally. Although, how they actually know that for sure, seeing as PLA (for 3D Printing at least) hasn't been around for 80 years yet, is unclear.

In addition, PLA can only be recycled at plants that have separate facilities that deal with PLA (as bio-plastics interfere with the recycling of other plastics if combined), and (as an aside) the fumes from PLA are not as harmless as many people think, due to the (up to 40%) additives.

So, PLA is not such a "happy" plastic as many people are led to believe by the marketing folks...

Greenonline
  • 5,831
  • 7
  • 30
  • 60
  • I don't think the existing answers are accurate and would like to see more information in the form of actual test results. There's a great deal of misinformation out there about plastics taking hundreds or thousands of years to break down, which seems to be at odds with easily made observations about what happens to things like plastic cups left outside for a few months to a few years. There's also the matter of structure and whether it's crushed/shredded, think objects to begin with, or a thick object with high infill. – R.. GitHub STOP HELPING ICE Jul 17 '21 at 03:01
  • 1
    @R..GitHubSTOPHELPINGICE Regarding where those plastic cups go to: [The big problem of microplastics](https://www.nottingham.ac.uk/connectonline/research/2018/the-big-problem-of-microplastics.aspx). – Andrew Morton Jul 17 '21 at 19:55
  • Also worth Noting: CNC kitchen's experiments of 2021 – Trish May 25 '22 at 07:52
0

PLA products will take up to 6 months to degrade in commercial composting facility. In home composting facility, it may take longer time.

Source: http://www.biogreenchoice.com/category_s/1866.htm

Dampmaskin
  • 202
  • 1
  • 3
  • 5
    Based on the way they treat grammar, I have doubts about reliability of that site: *How is unique about PLA and how it is different than regular plastic?* – Tomáš Zato Feb 15 '17 at 15:13
  • 1
    Based on tests conducted by several groups, the claim is simply wrong. – Trish May 25 '22 at 07:21