With Enzymes, A 'Create the Future' Winner Builds Self-Destructing Plastic

Billy Hurley, Digital Editorial Manager

The world has produced a lot of plastic — more than 8.3 billion metric tons, in fact, according to a 2017 study .

And from that giant mountain of bottles, food wrappers, and grocery bags, over 6 billion tons are left behind as waste.

A team that formed at the University of California, Berkeley aims to make the plastic problem disappear. Led by UC Berkeley Prof. Ting Xu and former UC Berkeley doctoral students Chris DelRe and Aaron Hall, the researchers created a compostable plastic that degrades when triggered by warm water.

The self-destructing plastic, and its inventors, won the Grand Prize of the 2021 Create the Future Design contest  — an annual competition from SAE Media Group that awards the year's best engineering ideas. The 2021 competition, which announced its winners in September, received entries from 55 total countries.

How Biodegradable Plastics Are Getting Better

Biodegradable plastics exist, but they traditionally require some help from the outside. Yeast strains, for example, can excrete enzymes that eat away at the compostable material, but the process is inexact.

"They're sitting on top of this plastic to basically cut this plastic up," Hall told Tech Briefs. "It's kind of like taking a pair of scissors and sticking it in a bowl of noodles and just sort of cutting randomly in there and hoping at the end that you completely degraded this thing away."

In early 2021, the team demonstrated a better idea: embed the enzymes from the very beginning.

The UC Berkeley-led process places polyester-eating enzymes into the plastic as it is made. The enzymes are protected by a simple polymer wrapping — like PPE, says Hall — that prevents the enzyme from untangling and becoming useless.

When exposed to heat and water, the enzyme becomes active, "chomping" the plastic polymer into its building blocks.The platform works with a variety of polymers, including the most common bioplastic polylactic acid (PLA). After degrading, it becomes lactic acid, which can feed the soil microbes in compost.

The enzymes start cutting the plastic up from the inside out, according to Hall, and that leads to a different degradation.

"Instead of sort of randomly cutting, we're now taking one polymer chain at a time — just one of those noodles — and completely destroying it into small molecules," said Hall. "And then we grab the next one and do the same thing. And this happens very, very fast without producing any microplastics."

Hall has since spun-off the team's research and founded the biotech startup Intropic Materials , based in Oakland, CA.

In a Q&A with Tech Briefs below, Hall reflects on his team's "Create the Future" win and offers a vision of the kind of future he imagines when plastic can truly disappear.

Tech Briefs: Now, can you retrofit this self-destructing mechanism, or does this have to kind of be added at the same time as you're building something?

Aaron Hall: Our goal is to scale this up to have this be something that you could drop into the existing infrastructure for the bioplastics, during the same time you would add in things like colors or property modifiers.

Tech Briefs: And where do you envision this kind of plastic being used first?

Aaron Hall: From the technology standpoint we can put this in right at the resin level, so very early in the process.

That's really exciting because it opens a lot of different directions that we could go. One area we can think about: food packaging. That's a huge part of the plastic waste problem: all of our single-use food and personal care. Because those are often very low-value items, it's often hard to justify recycling. If we had a very easy way to either compost these items away or degrade them in a really simple infrastructure, I think that could be a really big benefit.

There's also the opportunity to look at more high-end applications like 3D printing.

Tech Briefs: Why do we have so many plastics and plastic products in the first place, do you think?

Aaron Hall: Plastics are kind of these miracle materials. They're very lightweight, they have incredible properties. We save a lot of energy on shipping compared to putting in something like glass or metal. But the end of life for plastic really a challenge, right? It's not so easy to collect those lightweight low-cost items and turn them back into something that you get value out of.

We haven't had plastics for that long, and so I think there's really a reckoning right now: We're asking, “How can we get the best of the plastics that we had but also address this end-of-life consideration?”

Can we think about the end of life, right at the beginning? Bioplastics offer a promise to actually do that.

Tech Briefs: Why has addressing the plastic problem with bioplastics been such a challenge?

Aaron Hall: The goal is that we would source bioplastics from renewable sources and then, at the end of their life, they could be composted and turned back into soil and returned to the Earth and used in a cyclical fashion.

That's beautiful, but it's not that straightforward to do for a variety of reasons. There just isn't enough infrastructure yet to really do that composting.

Another reason: There's a lot of cynicism and distrust. There needs to be a strong demonstration that these plastics do fully break down, that they don't produce microplastics, that they're compatible with the infrastructure, and that the infrastructure is available.

Where I see us being able to really help with that missing piece is by being extremely rigorous with the science, to prove out that this does fully degrade away, completely down to benign small molecules – not micro plastics, not something that's going to ruin the environment.

Tech Briefs: What kind of infrastructure does your process require?

Aaron Hall: Our materials degrade in compost or in warm-water baths. With the warm-water bath degradation, we can think about very simple infrastructure that could degrade the plastics in these warm-water tanks and then collect those degraded products and send them back to be turned into fresh-quality plastic, which I think is another very exciting opportunity because, of course, compost is not going to catch on everywhere. There are some places where it’s just not realistic. Maybe there are land constraints or cultural restraints. These hot water baths are an exciting opportunity that we can explore.

Tech Briefs: How do you trigger this self-destruction?

Aaron Hall: Once the enzymes are embedded inside the plastics, we can expose them to water and heat.

It's not sufficient to just have one or the other; you do need both. In our preliminary studies, we’ve shown that 50 to 60 degrees Celsius is suitable for that.

In terms of water, it's either submersion into a water bath or submersion in a compost-type, wet-soil environment. We're now expanding and looking further at potential degradation environments, and exploring what would happen in a home-compost type of environment, and what would happen possibly in the landfill.

Tech Briefs: Because we have so many entries in such a range of technology areas, I often find that the grand prize winner is kind of a reflection of high-priority challenges that we're facing in the world. How does your technology reflect that kind of challenge?

Aaron Hall: There were a lot of really phenomenal entries, and it was a huge honor to be chosen as the grand prize winner. Societally, I think we're facing some questions about our environment. We've seen the climate-change reports coming out. There's a lot of evocative imagery being shown of waste, and especially a lot of plastic building up in in the ocean and in the environment.

I think the pandemic has played a role in elevating some of those concerns too, with people being at home. E-commerce is growing at the insane rate that it is, and people are receiving so many packages and seeing all the plastic, and learning that we can't just ship this off somewhere else, to offload this burden to some other country on to some other community.

We really need solutions that address the challenges holistically and that consider the end of life from the very beginning of the process. While we do that, we also recognize that people and consumers don’t necessarily want to give up all of the convenience and the benefits of modern society.

That’s a tension: I need to do better by the Earth, but also I don't want to give up my meals on the go. I don't want to give up durable, robust packaging. Not everyone wants to go back to farmsteading and homesteading.

We need better materials that maintain the quality and at the same time have a better end of life. And I think that's what we're chasing at Intropic. When I was at Berkeley and we were working on the project there, that something that was definitely at the front of mind: Can we take advantage of all of the benefits that we had while delivering more sustainable, bio-inspired designs?

What do you think? Share your questions and comments below.

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