Researchers at King’s College London (KCL) have pioneered a ground-breaking method for degrading and recycling single-use bioplastics. Roar sat down with Dr Alex Brogan to discuss the breakthrough.
Through this new method of recycling products like coffee cups and food containers, the team hopes to achieve a circular economy for bioplastics.
Published in Cell Reports Physical Science, this novel chemical recycling method uses an enzyme commonly found in biological laundry detergents to break down bioplastics into soluble fragments within 24 hours. This is about 84 times faster than the usual 12-week-long industrial composting process used for recycling bioplastic materials. After a further 24 hours at 90°C, the bioplastics break down into monomers – single molecules that form their chemical building blocks. These can then be used to create new products.
Susana Meza Huaman, a PhD researcher on the project, is incredibly excited by its potential applicability.
“For me the whole concept was fascinating! We used chemistry to stabilise a common enzyme at high temperatures and it was able to degrade post-consumer PLA plastic. I was very happy that the enzyme was able to depolymerise the plastic cup I used to drink an iced coffee. Moreover, while analysing the thermostability of the modified enzyme in ionic liquids, I was surprised by the fact that the enzyme looked happier at higher temperatures, it was a good indication that the enzyme would be active at those temperatures.”
Dr Brogan said that targeting polylactic acid (PLA) plastic in particular was an obvious choice. “[Choosing] the target was quite easy… I remember going to a beer festival [a] few years ago and being a little bit wound up by the [fact that] they were so proud of the fact that it was completely carbon neutral. And they’re like, look, we’ve got biodegradable plastic cups! [But] they’re not recyclable and you can’t just put it in your compost bin at home and you know, and they were absolutely gobsmacked by this… You’re almost generating a new problem by trying to have a non-oil-based plastic and replacing it with something that we can’t really deal with.”
PLA plastic is widely used in single-use food containers, cutlery, cups, packaging, and so on. However, these days polyethylene terephthalate (PET) – a slightly more recyclable oil-based plastic – is more commonly used. Brogan worries that this is a step backwards for sustainability.
“Since that beer festival, what I’ve noticed is that… if you actually look at the bottom of cups, a lot of cups these days, it no longer says PLA. It says polyethylene. People have moved back to using oil-based plastics. They’re slightly easier to recycle, but I don’t know, I feel like it’s going backwards. So that’s why we kind of wanted to look at bioplastics, [and] trying to recycle bioplastics in a genuine way.”
When it comes to sustainable resource use, the current landscape is nuanced and messy. Sometimes, the more environmentally friendly choice can be counterintuitive.
“It’s a really complex situation, and my favourite touch point for this is [that] there’s an uproar about using plastic bags for vegetables. The one that comes to mind is, [when] you get peppers in trios in a little plastic bag in the supermarket. It’s always in threes. There was a really interesting study done that showed [that] actually, it’s more efficient to transport peppers in stackable chunks of three like that in a bag than it is to deliver a crate of peppers on their own. And so, in terms of your carbon footprint, it actually makes more sense to package them in the plastic bags, so that then brings you to quite a big problem in terms of balancing the impact on the environment in terms of plastic waste, or the carbon dioxide [output] which is only going to make climate change worse.”
For cutting down plastic use, a delicate balancing act exists—especially when considering single-use food packaging.
“It’s a really fascinating problem because if we were [to just set a] blanket ban on plastic packaging, then the food waste would shoot up [and] we’d have to have less in our supermarkets, which, I think [there] is a balance to be made there. I don’t think we should be demanding so much fresh fruit all the time, but that’s the way [it is]. That’s where we’re at, and there are things that need to be done anyway. So taking that on board, we do need these materials.”
In today’s age, completely eliminating our use of plastics is not always a viable option, but transitioning to bioplastics can help ease the environmental impact. “We can’t phase out plastics. I think too much of modern life and things that people are used to—actually important things [like] medical devices and stuff would just rely on plastics to be around. But we can move to things that don’t require oil.”
One of the biggest difficulties with transitioning to bioplastics is the difficulty involved in recycling them and the drawbacks of their means of production.
The current ways we produce bioplastics are expensive and compete with farming for land use. And mechanical recycling methods are largely inefficient, generating mass amounts of carbon dioxide and failing to produce high-quality reusable materials. In the end, many of these ‘green’ plastics end up in landfills after a single use. This new discovery offers hope that this situation can change.
“The argument against a lot of bioplastics is that they’re not really recyclable which means that you have to make them as virgin materials over and over again, which would require a lot of land. And so being able to make bioplastics more recyclable then should mean that we don’t have to use as much land and we don’t generate as much waste, [which] should make it more attractive.”
Given the complexity and urgency of the situation, a multilateral approach may be necessary to ensure a more sustainable future. “I think [change] needs to be driven by the industry, but they need to be held accountable to make sure that they are using the most sustainable option possible.”
Dr Brogan is optimistic about the potential for the widespread application of his team’s findings. “Being able to introduce a more circular economy for bioplastics or something, that would be [something that we would] very much like to see… [The research] is driven by applications of science and so it seems a bit pointless if you’re driven by applications to then not try and follow that through.”
