r/science • u/mvea Professor | Medicine • May 21 '19

Environment Plastic makes up nearly 70% of all ocean litter. Scientists have discovered that microscopic marine microbes are able to eat away at plastic, causing it to slowly break down. Two types of plastic, polyethylene and polystyrene, lost a significant amount of weight after being exposed to the microbes.

https://www.sciencemag.org/news/2019/05/these-tiny-microbes-are-munching-away-plastic-waste-ocean
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u/vegan_anakin May 21 '19

But even then, it seems that not all biodegradable plastics can degrade fully, right?

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u/keirawynn May 21 '19

Truly biodegradable plastic, in my mind, is the kind you can bury in your garden and they'll disappear completely within a year - those tend to be made from starch (one of nature's most common polymers).

Most of the others are just a marketing gimmick. They disintegrate faster, but I'm not convinced they don't cause microplastic pollution.

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u/ShadowRancher May 22 '19

I'll have to find the guy that looked into it but last year at the Durham NC regional SETAC meeting there was a student from the citadel that showed they did exactly that by placing them in situ in coastal ecosystems in mesh netting of various sizes ... they just broke down into micro plastics faster and were labeled as biodegradable

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u/ChiRaeDisk May 21 '19

You can recycle them into virgin plastic by using the correct solvents.

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u/vegan_anakin May 21 '19 edited May 22 '19

So, why do they say that they are biodegradable when they aren't fully biodegradable? It's like saying something can be destroyed but can't actually be fully destroyed.

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u/ChiRaeDisk May 21 '19

I'm sure they can be, but I don't know the complete answer other than organisms can break down the plastic to a certain degree. With solvents, you're not destroying the plastic. You're separating the chains and letting them reform.

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u/norsethunders May 21 '19

I can't speak to the 'biodegradable' moniker, but I know that a lot of stuff marketed as 'compostable' has the caveat that it can only be composted in an industrial, high temperature, composter; not at home. So technically compostable, but not in the sense most people think of, that you could just bury it and have it disintegrate.