Instant Genius - Mark Miodownik: Are biodegradable plastics really better than traditional plastic?

Episode Date: February 17, 2020

You’ve probably bought something from a corner shop and taken it home in a plastic bag that says it’s biodegradable, or eaten takeaway food with a compostable fork. But when you’re done with your bag or your fork, what do you do with them? Can you put them in your food waste bin, your compost heap, or even the recycling bin? To find out, we spoke to materials scientist Professor Mark Miodownik. Mark is leading the Big Compost Experiment, a nationwide citizen science experiment to explore whether home-compostable plastics really do compost in your garden. If you sent us a question for Mark, listen out for his answer towards the end of the episode. If you have a burning science question you want an expert to answer, send them to us on twitter at @sciencefocus, and we may answer them in a future episode. Subscribe to the Science Focus Podcast on these services: Acast, iTunes, Stitcher, RSS, Overcast Let us know what you think of the episode with a review or a comment wherever you listen to your podcasts. Listen to more episodes of the Science Focus Podcast: Solving the plastic problem – Mark Miodownik How can we save our planet? – Sir David Attenborough Chris Lintott: Can members of the public do real science? Dr Erin Macdonald: Is there any science in Star Trek? John Higgs: Are Generation Z our only hope for the future? Mark Lynas: Could leaving nature to its own devices be the key to meeting the UK’s climate goals? Hosted on Acast. See acast.com/privacy for more information. Learn more about your ad choices. Visit podcastchoices.com/adchoices

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Visit name audio.com. to learn more. There isn't any such thing as a sustainable material. You know, people say, this is a sustainable material, that's a sustainable material, and they're wrong. There is no sustainable materials. Paper is not sustainable. Steel is not sustainable.

Glass is not sustainable. Things are not sustainable in their own right. Only a system can be sustainable. And what I mean by a system is someone manufactures something out of steel. You use it like your car or your razor. You then dispose of it. It gets recycled and then it goes back into the system. You're listening to the Science Focus podcast from the BBC Science Focus magazine team,

with the UK's best-selling science and technology monthly, available in print and in several digital formats throughout the world. Find out more at sciencefocus.com or look out for us in your app store. Hello and welcome to the Science Focus podcast. I'm Sarah Rigby, online assistant at BBC Science Focus magazine. You've probably bought something from a corner shop and taken it home in a plastic bag that says it's biodegradable, or eaten takeaway food with a compostable fork. But when you're done with your bag or your fork, what do you do with them? Can you put them in your food waste bin,

your compost heap, or even the recycling bin? To find out, I spoke to materials scientist Professor Mark Mia Dovnik. Mark is leading the big compost experiment, a nationwide citizen science experiment to explore whether home compostable plastics really do compost in your garden. If you sent us a question for Mark, listen out for his answer towards the end of the episode.

And if you have a burning science question you want an expert to answer, send them to us on Twitter at Science Focus and we may answer them in a future episode. So a lot of retailers are now looking to move from single-use plastics towards biodegradable or compostable materials instead. But what makes a material biodegradable or compostable and how can you make that into a material that looks and feels like plastic? Well, plastics are made of long, chain carbon molecules. And so polythene, for instance, is lots of little ethylene molecules linked up. And they create this sort of plastic material, the plastic bag material, which is, you know, strong and tough and light and, you know, does so many great things for us.

And there are lots of these so-called polypropylene, P.T, which is the drinks bottles material, HDPE, which is what you have your milk puddles in. So it's a very important material, but it turns out that most of the of life is also involves long chain carbon molecules.

So you can get you can get these long chain carbon molecules from things like corn and starch and so you basically harvest a crop. You use that as your carbon source and you create polymer

based on those. And it turns out those polymers, which we would call bioplastics, and the bio comes from the fact that we're taking the carbon from a biosource, like a crop residue, potatoes or corn or something like that, those polymers work the same as the ones we derive from petrochemicals. But you can go one stage further, and you can make them sort of tasty to microorganisms, little bacteria will eat them. And this is where biodegrades. radiable plastics come from. So you make something like a plastic, you take it from a source of carbon, which is a crop, let's say, and you make it so that little bugs like to eat it. And so now, potentially, you have like, oh, wow, that sounds great. Isn't that the whole thing sorted?

Yeah, so it does sound great. So now you've got this material which, you know, it didn't take fossil fuels to produce it and should be able to, you know, sounds like you can just drop it in your food, waste burn or stick it in your compost heap and then it'll just degrade but that's not quite true is it? No, there's a slight problem with it at the moment and that's not to say that in the future we're going to be able to sort it out but at the moment in order to get the properties that we need from plastics, i.e. for them to last let's say six months or a year protecting your food from, you know, imagine a crisp packet made of them for instance. You know, you want it to last a long time without being eaten by bugs. Otherwise, it would go off in your cupboard or it would go off while being

sent on a truck somewhere. And you've got to remember, these things have got to survive humid environments, hot environments. And so in order to get the plastics to be as good as that, you often have to do things chemically to them. And that makes them less easy for bugs to eat. And that means that their biodegradability requires certain conditions for it to happen. So most of the biodegradable polymers will only really biodegrade at temperatures of 50 or 60 degrees, for instance, in particular conditions of what's called an industrial compost. So you might get something like a biodegradable wipe, and it says biodegradable on it. But unless you put that thing in an industrial compost at the right temperature,

the right humility with the right bugs, it will not biodegrade. It'll still be in the environment. A year later, if you put it in the sea, it'll be there for years. Right. So if I go out and buy a coffee

and get that coffee in a biodegradable cup and I'm walking around town drinking it, what do I do with that cup? Well, you need to get it to an industrial composter, but there are not very many of them around and you don't see bins saying industrial composting. So you're forced to think, well, I'll either put it in the recycling, because it sounds like it's a sort of a green thing, so maybe recycling.

But the problem with that is it will contaminate the recycling. It's not meant to be recycled, and it won't be. So you really should put it in the bin, which is general waste bin. And the problem with the general waste bin for that item is that it will go to landfill. And in landfill, you might think, oh, great, well, it'll buy the grade there. But as I said before, it doesn't have the right. conditions in landfill either, so it'll be there for years, maybe decades. We know when we go back to landfill sites from 30, 40 years ago and dig them up, that there is still newspapers that

you can read. And I mean, clearly newspaper and paper is biodegradable, but it doesn't biodegrade under those conditions. Wow, that's quite surprising. So in a sense, these biodegradable cups then are less good for the environment than, say, if you had a recyclable plastic? Well, exactly. If you have a recyclable plastic, then you know where to put it. You put it in recycling. We have systems in place. I know there's been lots of TV programs about the scandals about that. But the truth is that UK does have systems recycling and is doing more and more in this area. And now the public outcry is making that even more. So you can support recycling and it does get recycled by using recyclable plastics.

And the good thing here is that you're hanging on to the carbon. So having got it from, let's say, a crop, if actually you just biodegrade it in industrial composting, and potentially you're putting the carbon back in the atmosphere. And what we really want to do is keep carbon in the system because as we know, as we know, we're trying to get rid of carbon dioxide out of the atmosphere. So recycling, in my view, really is the thing that most of these replacements, you know, for containers and packaging should be. We want everything to be recyclable,

and we want to recycle it. There are a few things you might think shouldn't be or difficult, and so biodegradable plastics, you can imagine, you know, having a place, and one of them you may already have seen, which is something called home compostable, biodegradable plastics. Now, you get these sometimes in newspaper wrappings

or membership magazines, and it says home compostable. And what that is, is they usually, the plastics themselves are not mechanically, usually very strong, but it's okay because they do the job they need to do. And then you have them at home, and then you'll encourage to put them in your home compost if you have one. But it's not clear to us, so I run a research group called the Plastic Waste Innovation Hub at UCL, and it's not clear to us that the people who are selling those home compostable plastics know whether they really will

compost in every single type of home compost. Because if you think about it, it's a very difficult thing to do because you imagine you're in the north of Scotland. You know, the temperature and humidity up there is so different from the south of England. And how do you make sure that these things biodegrade completely in someone's compost? It's very hard to do it, I mean, to really guarantee it. So we've started something called the big compost experiment. It's the citizen science experiment.

Anyone can join. if you Google that term, big compost experiment. And you can join in to do this experiment. You know, take a piece of home compostable plastic that you might have received or got in your hands and put it in your compost and send us the photo and the website shows you how to do this. And then we are, you know, as a nation,

can do this experiment and see if these home compostable biodegradable plastics really do do that. So members of the public can get involved and figure out how well these plastics could biodegrade in their own garden? Yes, exactly. And here's the other thing. I know that many people don't compost, and they might think it's an old foie thing to do. Usually, I mean, in my experience, the people who compost are the people who are keen gardeners, because you need compost to garden. You need fresh, you know, soil, and that's how you get it is from your compost. But I have to say, having been someone who's composted for 20 years, it's such a miraculous system because it's one of the few sustainable systems we have. You put things in like peelings and food waste and leaves. out of the bottom of it comes lovely earth and all the work is done for you and it's quite miraculous and I think knowing about that system if you're not if people out there are not

already composting I think do join in because not only will you help us understand the problem of biodegradable plastics or whether they're good or bad but you will also I think get a huge amount personally out of it yeah so home compostable plastics do sound like a great solution for people who have access to a garden where they can have their own compost pile. But especially as the population increases, there are going to be more and more people living in, say, flats without necessarily access to a garden. So how could we address that to make sure everyone has access to a compost garden? Would we be able to say, give everyone access to an industrial composter? Or do you think there's another solution that would be more suitable? Yeah. So I think this is all to play for.

And I think, again, this is why we all need a citizen to engage with this, because there's a lot at stake here. What we don't want is to go down a route that's going to cause more environmental harm. And potentially, that's the case at the moment because we're not really thinking about this clearly. It turns out that of a person's normal been at home, 50% of it is food waste. And that's really problematic, not just because of the food waste, but I mean, everyone has potato peelings and of this, that and the other. So everyone's going to have some food waste. I'm not sort of trying to to say to people they're wasting food, but it's still a lot of your bin. And that goes, as it currently does at the moment, to a hole in the ground, landfill. What happens to that is it then ends up in,

as I say, in these conditions that are not good for biodegrading. And in fact, it mostly creates methane, which is 28 times more potent greenhouse gas than common dioxide. So one of the big ambitions of the government and everyone should be to get all of that food waste out of that bin and to be composted. So there's an ambition for the government and for all of us, essentially to separate your waste. The most important separations you can do are the recyclables go in one place. The food waste should go in a composting bin and the rest should go somewhere else. Now, what you do with that composting bin, as I say, you're really helping everyone and climate change. If you can do this, you use my, well, I live in a flat. What do I do with it? And I think that's a really just

thing, you should be asking for someone to collect this or participating in a communal compost scheme and they do exist. And as I said before, there is something really wonderful about participating and you're also doing something really great to mitigate climate change. Okay, great. So if we have these biodegradable or compostable plastic materials which aren't necessarily biodegradable or compostable and they can't be recycled, As they are at the minute, is there any real value in us having them at all?

I mean, I think there isn't any value at the moment because we don't have, there isn't any such thing as a sustainable material. You know, people say, this is a sustainable material, that's a sustainable material, and they're wrong. There is no sustainable materials. You can't paper is not sustainable. Steel is not sustainable. Glass is not sustainable.

But things are not sustainable in their own right. Only a system can be sustainable. And what I mean by a system is someone manufactures something out of steel, you use it, like your car or your razor, you then dispose of it, it gets recycled, and then it goes back into the system. That's a system,

and that can be sustainable if you can make sure that you're using the energy properly. Paper's the same. There is a recycling system for paper, and paper goes back into recycled paper. But plastics, you know, the way to deal with plastics

is to have a system, and the recycling is the system. If you then try and say, well, we're going to do biodegradables, what you're trying to do is create a system in which the atmosphere CO2 plays a part, and it seems to me that we're already problematically dealing with CO2 in the atmosphere. So this is a difficult system to become sustainable, in my view.

Yeah, absolutely. And so as a lot of retailers are taking on these biodegradable and compostable materials, some others are swapping single-use plastic for other single-use materials like paper, or glass, but they're still single-use materials. So would you say there's any value in swapping plastic for something else that, again, will just be used once? Well, again, you've got this problem. There is a system for paper recycling, but if it's contaminated with food, it won't be recycled. And actually, paper uses more energy and water in general than plastics.

So you're potentially making the water issues worse and climate change worse by swapping one single use material for the other. And I think this is also true of glass. So the truth is that I think people are so alarmed with plastic and disgusted about the pollution. And they're right to be disgusted. But what we don't want are these knee-jerk reactions, which really are greenwash. They're sort of placating people. Or we're doing something about the problem. but I think the inherent way to do something about the problem is to change the system,

and we need systems change, and it sounds abstract, and I think that's part of the problem. It's very hard to see systems change. But definitely we don't, I think, want to continue doing single-use-anything. Okay, so what sort of system changes would we need to put in place to get rid of single-use materials as much as possible? So one of the things we need is reuse to come back more in our lives

because if you reuse a container many, many times, then you reduce the amount of energy required to make it and also you minimize the pollution associated with it. So things like coffee cups, for instance. At the moment, there's a real problem with them because they're mostly disposable single use and we don't really have a system for dealing with that and putting those cups and making new cups out of them. So in my view, we should stop using them and we should go to reuse.

Now, it used to be that you went into a cafe and you bought a coffee and you couldn't get a takeaway coffee cup because it just no one expected to be able to do that. You sat in the cafe and you drank your coffee. But now we've kind of got used the idea that actually you do go into a coffee shop and buy tea or coffee or hot chocolate. whatever, and you then walk away with it. And so we've got this challenge in society to create a reuse system for coffee and drinks that allows people that freedom of movement. I don't want to stop them doing it. But isn't about that then item just gets disposed on.

And how would that work? I think it's actually doable. I think we just need to think more communally about cups and a cup system that might be standardized across a whole community. you might prepare deposit so that, you know, you've paid some money for it. And then you get the money back when you give the cut back. It doesn't seem too difficult to me these days with digital, you know, credit cards and so on. You know, I think it's doable and it's much better system.

Yeah. So I do quite a bit of cooking. And so I have a fair few cooking things which are made of silicon, reusable silicon, so things like reusable silicon piping bags or like a silicon spoon as opposed to a plastic spoon or things like that or cake tin liners or cupcake cases that are made of silicon instead of paper. So you can use them over and over again, but then thinking about it, I have no idea what you do with silicon at the end of its life. So what do you think about using sort of flexible silicon materials for these sorts of purposes?

Yeah. So I think reuse is better because when you look, when you think, when you think of, about the crisis that we face environmentally at the moment, the biggest one is climate change. And you reusing those items many times, the CO2 emissions of that, depending on how many times you reuse them, but let's say it's 20 or 30 or 40 times, and maybe up to 100 or 200, you know, then you're really, really getting the, we all as a society are benefiting from you doing that. So the problem is with reuse, if you only use them a few times, let's say five or six times. And then the energy involved in making them in the first place doesn't outweigh

disposables. But then, of course, everything comes to the end of its life at some point. And you need to have an, you know, I was talking about a system. And what is the system for recycling silicone rubber? You may ask, answer, there isn't one. So, I mean, the best scenario is it will be, it will be incinerated if they end up there and create a little bit of energy for the society. but the car, you know, it's not a good scenario really. So we need to start moving towards not just things that are reused many times, but at the end of their life, they also have a system for recycling. This is a much bigger problem than just your, I mean, it's great that you're doing that,

but if you think about most of the things in your life, how many of them are, is there a recycling route for? You know, not that many. I mean, clothes are not really recycled very much. much because they're mixed fibres and that's a real problem. Phones, furniture. I mean, most of it, there's a reuse market, which is great. So selling things secondhand, buying things second hand,

that's really good for the environment. And it's probably the way forward for those things. But we also really need to change all of our systems and probably change the way design happens. We should never really make something. We should never be allowed to sell something unless you can prove that at the end of its life, there is a system for collection and remaking.

That would be quite a radical change in the system. It is a radical change, but I just don't see any other way forward. We have got used to this idea that there's a big hole in the ground somewhere we can put things into, and it just isn't. And so basically that everyone's designed things with no end of use, end of life in mind. So I'm looking at my table here and there's a monitor, a screen, which we've got liquid crystals in it and it's got a glass front and it's got loads of electronics in it. And almost none of that will end up back being made into a screen again. There's a loudspeaker, there's a keyboard, there's a fan. You know, it really saddens me that we've, you know, and I think we'll look back on this time with kind of complete incomprehension.

how could we make things, this amount of incredible stuff, and not think, well, what are we going to do at the end of its life? But that is what we've ended up doing. Yeah, absolutely. So now I'd like to move on to some questions that people have sent into us on Twitter. So I'd like to thank everyone who sent in a question. So first of all, Natalie Dyer asks, what are the resulting carbon emissions from the creation of compostable and biodegradable plastics

compared to regular plastics? Yes, so we've been doing a life cycle analysis, so-called. This is how you, this is how, it's not just the carbon emissions, but it's also amount of water you use and other things, other environmental things. And bioplastics and biodegradable plastics come out usually quite well out of this. They're not, you know, it requires energy and it requires water to make these. But it is quite good compared to the petrochemical. the only problem comes when you look at how they're actually used in practice.

Because often their mechanical properties are poorer, which basically means you use more of them in order to make up for the fact they're not as strong or as tough. And then when you factor the extra weight in, then they start to get worse. I know it sounds really kind of subtle, but it is just kind of one of those things. As soon as you start talking about millions of these things, and we are, we are talking about growth in a sector that's going to be huge hundreds of millions of tons, then you really should worry about this. The really good side of it is if you can make bioplastics not biodegradable, okay, you can make them like normal polymers that can be recycled. So you can make a bioversion

of polypropylene and you can make a bio version of polypropylene. And then they're fully recyclable. So you keep the carbon in the system. And then you really gain. So that, to me, That's the way forward. We should be using crops and crop residues to make our plastics in the future, not oil. We should be leaving oil in the ground. And then we should be recycling it so we don't emit more CO2 afterwards. Oh, I see. Thank you. Lillia Gibbons asks, if you have limited funds, what's one eco-switch that could make the most impact on the earth? Wow, okay, limited funds. I mean, the only unambiguously, environmentally good thing to do at the moment, given that we don't have very many systems that are sustainable, is to reduce your consumption of everything.

Because if you reduce your consumption of everything, you are definitely doing the environment good. And actually, in a way, it doesn't cost you any money to do that. Could even save you some money. Yes. So I would say things like, if you took three flights last year, take one flight this year. If you bought 10 items of clothes last year, set yourself the target of only buying five this year. Just set yourself some targets that are clearly less than last years and you are doing a real favour to everyone.

And that's something that anyone could get involved with, regardless of how much money they have. agreed. And the other thing I'd say is to compost. And I know I would say it. But if you can get your food waste out of your bin, so it's not ending up in landfill, you are doing all the massive favour. It's not going to become methane. And then if you compost it or you put it into a communal compost or even you give it to your local authority, you are doing everyone a big favour. And that again, I mean, doesn't really cost you any money. Okay. Great. Rosie Mill Group, asks, I'd really like a clearer understanding on what plastics can and can't be recycled. I have regular family disputes over whether a yoghurt pot can go in the recycling.

Where do we need to target first when looking for alternatives? Great question. And we've all had those discussions. Yogurt pots are usually made, if they're ones where you crack them open, you know, part of a four-pack and you get that cracking sound to open them, that's, they're made of polystyrene. and that isn't recycled in this country and the reason it isn't recycling this country because it is recyclable and that word's weird isn't it recyclable but it doesn't get recycled

is because there's just not enough of the material to make it worthwhile you can't make money out of it you make it loss so we have been trying to encourage those manufacturers not to use polystyrene but to use one of the other plastics where there's a lot of it

because the ones that really do get pulled out and I've been to the systems and I've seen it happen is PET, which is drinks, bottles, material. That gets recycled and it's valuable. High density polyethylene, milk bottle material, that gets recycled and ends up in new milk bottles. I've seen the, I've seen, I've been to the plants.

And these, so what we really want to do is get the supermarkets to make all the trays and tubs and all the bottles out of three polymers maximum. And that way those all three of them, it would be very obvious what to do with them for a start because there'll only be three, and they're all recyclable, and they are polypropylene, high-density polyethylene, and PET. All the others are problematic at the moment from an economic perspective. And that's big, yeah, so that, I mean, that's, and they're all really good. So if you want to, say, look for an alternative for your yogurt pots, you could try and look for one that's made of one of those three materials?

I mean, I'm a bit of a saddo, but that is what I do. when I go, I look at the back and you don't look at, it doesn't, you just look at whether it's made of, you know, one of those three polymers. And if it is, you can, you can put it in your recycling. I have to say the other big problem in the UK is that we haven't got the same rules everywhere. And if there's one thing I want the government to do in the next few months is to just mandate that all the UK recycling schemes are the same. because then the supermarkets can then buy, with certainty, no, that they don't have to say, look, you know, they have this weird label that says check locally,

as if that's something you can easily do, which I don't think it is. Okay, thank you. And finally, Jack Bateman asks, some shops are now offering refill stations where you can bring your own reusable containers. But if your plastic container breaks, does it end up being worse for the environment than the thin single-use packaging that you would have had?

Yeah, so that's what I was saying about reuse. That reuse only works if you reuse things a certain number of times because usually the reuse item is cost more energy, it has more mass. It's usually slightly thicker than the single item. Because it needs to last longer. And that costs your energy and CO2 emissions and water and so on. So yes, it's the right question to ask because it's basically how many times you have to reuse something for it to be viable.

And let me just say, you know, something as simple as a cup, you know, your mug of tea at home, you know, ceramic, is that sustainable, you might ask. Well, you know, you have to use that 200 times for it to be better than to use a single-use plastic cup. Wow. Now, I'm sure at home people do use their cups 200 times. But if you're a very clumsy person and you smash your ceramic cup every 10 times, then, you know, then you need to get left. clumsy or have a sponge floor or something. Okay, great, thank you. So to sum up, what is the way forwards with single-use plastics? The way forwards with single-use plastics is that we, you know, I think we, we haven't really

talked about that fact that they reduce food waste. I think, I think the packaging that you see in the supermarket, some of it is just, you know, just to kind of make you feel good about yourself and to buy things that, that little colourful and things like that. But I, but, but, but, we're not going to reduce, we're not going to lose plastic from our lives because it's very useful. It reduces food waste. It reduces weight of almost everything. And it's very lightweight and tough for transporting goods across the planet. And, you know, all of that helps reduce CO2 emissions. So you're going to get plastics into your life. And we need to make sure every single plastic in a supermarket, let's say, is recyclable. And it all goes into one bin and you don't have to

make any head scratching decisions. And that is the future. And that, that is, plastic all get recycled back into new plastics, which then get used for more packaging. I think when you talk about plastics more widely that in our clothes. Now, you know, the average piece of clothing is 67% plastic, right? Our shoes are mostly plastic. You know, lots of stuff in our lives, including the phones, all the electricity that comes into our lives is all coated with plastic. It's all vital, but, you know, we just, we don't have any systems for recycling those yet.

And I think we really seriously fast need to redesign everything so that there are systems recycling everything in our lives. That was material scientist Professor Mark Miodovnik, talking about why a knee-jerk switch from single-use plastic to biodegradable alternatives could actually make things worse. The February issue of BBC Science Focus magazine is out now. In it, we look into the greatest mystery in science, what actually is consciousness? Now we have a message from our sister magazine, BBC Sky at Night.

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