REALITY CHECK
Retailers are under pressure to move away from single-use plastic. But could a knee-jerk reaction actually make things worse?
The science behind the headlines. This month: Are compostable plastics any good? Is Betelgeuse about to go supernova? What’s the deal with the Huawei 5G controversy?
Retailers are beginning to switch from single-use plastic to biodegradable, compostable or recyclable alternatives, according to research by environmental think tank Green Alliance. But could these quick fixes cause further harm to the environment? We talk to
Mark Miodownik, a materials scientist who’s leading the Big Compost Experiment. This nationwide citizen science experiment will explore whether homecompostable plastics really do compost in your garden.
HOW DO YOU MAKE BIODEGRADABLE PLASTICS?
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 bag material which is strong, tough and light.
It turns out that most of life also involves long-chain carbon molecules, so you can get these structures from things like corn and starch and so, you basically harvest a crop, use that as your carbon source, and create polymers based on those. These 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, so little bacteria will eat them, and then this is where biodegradable plastics come from.
HOW SHOULD WE DISPOSE OF BIODEGRADABLE AND COMPOSTABLE PLASTIC?
There’s a slight problem with it at the moment. In order to get the properties that we need from plastics, for them to last six months or a year protecting your food, you want it to last a long time without it being eaten by bugs. Otherwise, food would go off in your cupboard.
And you’ve got to remember, these plastics need to survive humid and 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. That makes them less easy for bugs to eat, and that means that their biodegradability requires certain conditions.
So, most biodegradable polymers will only biodegrade at temperatures of 50°C or 60°C, for instance, in the particular conditions of an industrial composter. You might get something like a biodegradable wipe, and it says biodegradable on it, but unless you put that thing in an industrial composter at the right temperature and the right humidity with the right bugs, it will not biodegrade. It will still be in the environment a year later; if you put it in the sea, it will be there for years. So, you really should put it in the general waste bin.
WHAT’S BETTER: BIODEGRADING OR RECYCLING?
If you have a recyclable plastic, then you know where to put it: you put it in the recycling. We have systems in place. And the good thing here is that you’re hanging on to the carbon. But in the case of a biodegradable plastic, having got it from a crop, if you just biodegrade it in an industrial composter then potentially you’re putting the carbon back in the atmosphere. What we really want to do is keep carbon in the system, because we as we know, we’re trying to get rid of carbon dioxide out of the atmosphere. We want everything to be recyclable, and we want to recycle it.
IS THERE ANY VALUE IN SWAPPING SINGLE-USE PLASTIC FOR THESE ‘BIODEGRADABLE’ MATERIALS THAT DON’T BIODEGRADE AND CAN’T BE RECYCLED?
I think there isn’t any value at the moment, because there isn’t any such thing as a sustainable material. Paper’s not sustainable, steel is not sustainable, glass is not sustainable. Things are not sustainable in their own right. Only a
“Most biodegradable polymers will only biodegrade at temperatures of 50°C or 60°C, in the particular conditions of an industrial composter”
system can be sustainable. And what I mean by a system is: someone manufactures something out of steel, you use it on 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 that can be sustainable if you make sure that you’re using the energy properly.
If you then try and do biodegradables, what you’re trying to do is create a system in which the 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.
IS IT WORTHWHILE SWAPPING SINGLE-USE PLASTIC FOR A DIFFERENT SINGLE-USE MATERIAL?
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 another.
So, the truth is that I think that 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 are really a greenwash. They’re sort of placating you, but I think the inherent way to do something about the problem is to change the system.
WHAT’S THE WAY FORWARD?
We’re not going to lose plastic from our lives, because it’s useful. It reduces food waste, it reduces waste of almost everything, and it’s lightweight and tough for transporting goods across the planet and all of that helps reduce CO2 emissions. In our clothes, now, the average piece of clothing is 67 per cent plastic. Our shoes are mostly plastic. Lots of stuff in our lives is all coated with plastic. It’s all vital, but 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 for recycling everything in our lives.
We need to make sure every single plastic in a supermarket is recyclable, and it all goes into one bin and you don’t have to make any head-scratching decisions. And those plastics all get recycled back into new plastics which then get used for more packaging. That is the future.