Big Compost Experiment on BBC Radio 4’s Inside Science

Adam Rutherford
Here on Inside Science we’re helping to launch a new citizen science project about the wonderful rich fruity and essential substance you can produce by doing not that much at all. It is compost. I visited architect Danielle Perkiss and Mark Miodownik, material scientist at UCL, both dirt-loving compost enthusiasts.

Mark Miodownik
So we’re on my roof in Central London. We can see the Tate, we can see St Pauls and there’s two compost bins next to me, these are my composts, they’ve been here for 20 years and all my food waste and my family’s food waste has been through these composts.

Adam Rutherford
OK so these are standard plastic compost bins. Sort of Dalek sized — actually they look a bit like Daleks.

Mark Miodownik
Black polypropylene. And I have to say this is one of the things that gives me the most joy in the world. It sounds ridiculous, I know, to say this but the fact that you put food waste into them, and here is one here, and then... look at that. I mean, that is biodiverse if you ever saw it. There’s tons of creatures in there eating away at apples and onions and all the bits that we've thrown out and they will turn into earth. I mean, I really find this alchemy.

Adam Rutherford
This is really active. There’s a lot of insect life

Mark Miodownik
And of course there’s fungus.

Adam Rutherford
And this is a sign of a healthy compost.

Mark Miodownik
It is a miracle. It never ceases to please me that you can take everyday household waste, food waste, put it in there and six months later out comes earth, and the earth is out here in these pots. This is actually earth from this compost which I cleared out. The basil, the salad, the tomatoes, it all comes from this, so it is just so wonderful, I find. I’m not trying to be smug about this, I just love it. But now, these days, things are coming through our door, and I’m going to show you one, which makes me wonder what I should do with this compost and here it is. I've got... it's a membership magazine. It’s in what looks like a polythene wrapper but it isn’t polythene because it says “I’m 100% compostable” and then it says how can you dispose of this, and it says in a well maintained compost heap. Well I have one of those, so presumably I should take this off here and put it in there. But… as a material scientist, I worry about that, because they haven’t told me what this material is, there are some directions on it, but it’s confusing, isn’t it? And then I look around and I see loads of things that say ‘biodegradable’ or ‘biodegradable packaging’, ‘this is not a plastic’ — what is it then? They don’t tell you. And that’s when I got in touch with Danielle Purkiss, here, who I’d like to introduce, who is an architect and a materials researcher. And we decided to put together a study. Let’s get the whole of the public involved in trying to understand whether the stuff that comes through our door that says ‘compostable’ is actually compostable.

Adam Rutherford
This is the Big Compost Experiment, Danielle, and it’s not just wrappers from junk mail that comes through our doors. Everything needs to be biodegradable these days. We buy things because they’re biodegradable, but I guess the question is: how biodegradable is it?

Danielle Perkiss
Well that’s one of the really important questions that we start off with in the survey: how do you feel about biodegradables and do you think that they’re actually better for using in society or should we throw them away or should we put them in our composters or not. Because it’s quite confusing, as Mark’s suggesting. A lot of the information that comes on the packaging, it’s not regulated yet. From my point of view, I recently started to keep a wormery at home, and it’s an indoor wormery. I also wanted to know what kind of issues there are around keeping things like a compost heap or a wormery when you have very little space — I live in a small council flat in North London. So yes, it’s been very interesting trying to look at the idea of ‘what is compost and composting’.

Adam Rutherford
Is one of the ideas that... well... we all assume that things being biodegradable is beneficial to the environment and therefore we should do it more, but I guess that’s the end of that moment of revelation. And you say it’s not regulated so companies can say “this is biodegradable” and therefore everyone’s happy with that, but actually that might not be… well it might be partially true.

Danielle Perkiss
The issue with biodegradables and compostables is essentially how long it takes that thing to break down and what it breaks down into. And because plastics are engineered, designed materials there’s a sort of level of complexity to what these things might then break up into and that’s the question we want to know: how long does it take the piece of biodegradable plastic or compostable plastic to actually break down; what conditions are needed for it to break down sufficiently; and whether or not it breaks down quick enough for it either to not cause an extra pollution problem if it’s released into the environment, for instance, and also to find out what the subsequent effect might be on the environment of your compost heap, so therefore where you put your compost afterwards. So we know that compost is used for things like feeding and enriching the soil for plants that you eat, or things that you might not eat, but there again we need to know more about that. So that’s why we need to gather some useful data about what the impacts are, of this material.

Adam Rutherford
So where I live, and I think this is relatively common in big cities, we collect our food compostables, and that gets collected once a week with the bins. We’re not even sure what bag to use in our kitchen caddy, though, because some of them fall apart after four days, some of them seem to be like plastic bags, and some of them are paper.

Mark Miodownik
Yes, it’s actually a problem for the people who deal with the collection of that food waste, because that is collected and sent to an industrial anaerobic digester to get biogas, so it’s a very eco thing to do, to collect your food waste. But the problem is that if you put you biodegradable plastics in there they will remove them at that place, and they’ll burn them, or put them into landfill. And the reason is because those digesters can’t take those plastics, even if they’re biodegradable plastics.

Adam Rutherford
So the assumption that anything that says biodegradable on the packaging… they all have to be treated differently.

Mark Miodownik
They all have to be treated differently and that's part of the thing we’re trying to discover with this. So even if you don’t have a compost at home but you put your stuff into food waste we still want to hear from you, because we want to know what your opinion is about these things and what you think you should do and shouldn’t do.

Adam Rutherford
OK so it’s called the Big Compost Experiment — plug the pluggables — what do people need to do to get involved?

Mark Miodownik
It’s called the Big Compost Experiment. You search for that, on the web, and you will find our website. It’s very simple, it will only take you one or two minutes to fill out the survey, and then it invites you to take part in the experiment, which you have to take one or two items of biodegradable plastics that say on them ‘home-compostable’. Pop them into your compost, take some photos just to show us what you’re doing, and then we’ll send you an email when it’s ready for you to have a look at what’s left.

Adam Rutherford
And there’s a hashtag so we can look at everyone’s juicy compost.

Mark Miodownik
Hashtag #BigCompostExperiment

Adam Rutherford
Yep — #BigCompostExperiment that was Mark Miodownik and Danielle Perkiss. Do get involved. We’ll be tracking this brilliant citizen science project as it begins to rot, degrade, smell and eventually turn into something utterly beautiful and terribly important.