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Bio-degradable plastic is a scam. https://www.nationalgeographic.com/environment/2019/04/biodegradable-shopping-bags-buried-for-three-years-dont-degrade/ https

Bio-degradable plastic is a scam. https://www.nationalgeographic.com/environment/2019/04/biodegradable-shopping-bags-buried-for-three-years-dont-degrade/ https://www.nationalgeographic.com/environment/2019/04/biode... https://theconversation.com/when-biodegradable-plastic-is-not-biodegradable-116368 https://theconversation.com/when-biodegradable-plastic-is-no... https://www.theguardian.com/environment/2016/may/23/biodegradable-plastic-false-solution-for-ocean-waste-problem https://www.theguardian.com/environment/2016/may/23/biodegra...

frazbin 6y ago
Here's the problem: Take a biodegradable bag and grind it up into dust, then sprinkle it on the ground-- no problem. Bacteria in the soil will eat it and turn it into biomass and gas. Do the same with a plastic bag, and the tiny bits of plastic will just stick around, and plants grown in that soil will be contaminated by plastic per the study. These bags aren't breaking down quickly simply because they are big. Decomposition is like any other kind of eating; you keep breaking the stuff down into smaller bits until it's gas and biomass. But with plastic, where biodegradation can't happen, the tiny bits (nanoplastics) accumulate. Fun fact about nanoplastics: we can't reliably measure them! We can make a reference solution and apply it to arabidopsis, but we can't count nanoplastic particles in wastewater. I'm told they can be as small as a protein molecule.
- markdown 6y ago
  > I'm told they can be as small as a protein molecule. Sounds about right given that we've just learnt that plants can take up plastic though their roots: https://www.nature.com/articles/s41565-020-0707-4 https://www.nature.com/articles/s41565-020-0707-4
hristov 6y ago
There are established standards for compostable plastics (ASTM D6400 in the US and EN 13432 in the EU). The products of the company I mentioned above comply with those standards as well as many other products I am sure. So if you are looking at a biodegradable product, you should check whether it complies with the above standards. It is better to look for "compostable" as that implies compliance with those standards (at least if sold in the US or EU). The standards have been criticized because they assume an industrial or municipal composting environment (which mostly differs from normal environments due to relatively high temperatures). So even if you have a compostable plastic it is better to put it in a compost bin and have your municipality compost it in an industrial manner. But the compostable plastic under those standards will degrade under normal environments too it will just take longer. Even in your article, the compostable bag disappeared in the underwater test and disintegrated in the open air test. It only survived the under ground test, probably because of lack of oxygen. So in summary compostable plastics should be composted and not just tossed away anywhere. But even if they are tossed away at random places they will degrade much sooner than actual plastics and thus present much less of a problem for the environment.
- everdrive 6y ago
  But you haven't answered the most important question here: is this plastic actually biodegrading, or is it just breaking up into plastic dust?

frazbin 6y ago

Here's the problem: Take a biodegradable bag and grind it up into dust, then sprinkle it on the ground-- no problem. Bacteria in the soil will eat it and turn it into biomass and gas. Do the same with a plastic bag, and the tiny bits of plastic will just stick around, and plants grown in that soil will be contaminated by plastic per the study. These bags aren't breaking down quickly simply because they are big. Decomposition is like any other kind of eating; you keep breaking the stuff down into smaller bits until it's gas and biomass. But with plastic, where biodegradation can't happen, the tiny bits (nanoplastics) accumulate. Fun fact about nanoplastics: we can't reliably measure them! We can make a reference solution and apply it to arabidopsis, but we can't count nanoplastic particles in wastewater. I'm told they can be as small as a protein molecule.

markdown 6y ago
> I'm told they can be as small as a protein molecule. Sounds about right given that we've just learnt that plants can take up plastic though their roots: https://www.nature.com/articles/s41565-020-0707-4 https://www.nature.com/articles/s41565-020-0707-4

hristov 6y ago

There are established standards for compostable plastics (ASTM D6400 in the US and EN 13432 in the EU). The products of the company I mentioned above comply with those standards as well as many other products I am sure. So if you are looking at a biodegradable product, you should check whether it complies with the above standards. It is better to look for "compostable" as that implies compliance with those standards (at least if sold in the US or EU). The standards have been criticized because they assume an industrial or municipal composting environment (which mostly differs from normal environments due to relatively high temperatures). So even if you have a compostable plastic it is better to put it in a compost bin and have your municipality compost it in an industrial manner. But the compostable plastic under those standards will degrade under normal environments too it will just take longer. Even in your article, the compostable bag disappeared in the underwater test and disintegrated in the open air test. It only survived the under ground test, probably because of lack of oxygen. So in summary compostable plastics should be composted and not just tossed away anywhere. But even if they are tossed away at random places they will degrade much sooner than actual plastics and thus present much less of a problem for the environment.

everdrive 6y ago
But you haven't answered the most important question here: is this plastic actually biodegrading, or is it just breaking up into plastic dust?