Biodegrading plastic

04 December 2018

Question

Biodegradable plastics for wrappers etc is seen as a way to reduce rubbish and a good thing. I'm wondering what chemicals end up going into the soil as the plastics break down. Is biodegradable plastic all good news?

Answer

Chris put Stephen's question to chemist Ljiljana Fruk...

Ljiljana - Yeah. So people are actually still working on all kinds of polymers and biodegradable polymers are a big thing. And there are lots of procedures out there to turn some of the natural polymers like cellulose is a natural polymer, or chitin - present in the shell of shellfish and in insects - is also a polymer that has been used to make some biodegradable polymers as well.

But I would like to point out here that maybe the biggest problem when we think about plastics is not design of biodegradable plastics in itself, because the industry and also the applications of the plastic. The industry will always look for processes which are cheaper and for now we have plastics and polymers which are way cheaper than biodegradable plastics. So maybe instead of also only focusing on biodegradable plastics, we also need to focus on finding the ways how do we recycle the plastics that we already have out there in the environment and how can we reuse it for something else? And I think this is more a question of the policy than the science.

Chris -  And this question about when these things break down, what they break down into?

Ljiljana - Yeah well the problem is - OK biodegradable plastics that will all depend on what is it made of? And so polylactic acid for example is biodegradable, so it wouldn't be as terrible as one would imagine. But you would still have a very persisting big parts of plastics which might end up in the stomachs of animals and then go through the system. We are still not out there that we could definitely find the biodegradable replacement for the plastic that already exists.

Chris - It's a good point though isn't something that in this era we need to focus on finding things that we know will not just rob Peter to pay Paul, because it's easy to brush this particular plastic waste under the carpet isn't it? And say “well it's biodegradable now” but you know what it turns into is pretty important.

Ljiljana - Exactly so I think more focus should be done first on how do we deal with plastic waste and replace types of plastic that are already there. We are not just going to stop making them. And the second thing, could we may be taking cues from the real bio-polymers like as I said so cellulose and chitin which have natural mechanisms of breaking down. So I think this will be the direction that science will focus in the future and it's focusing now as well.

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