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How This Chemical Engineer Is Hacking Plastic Production To Promote Sustainability

A recycling plant worker sorts enormous piles of plastic bottles.
Koji Sasahara/AP
A plastic recycling company worker sorts out plastic bottles collected for processing at Tokyo Petbottle Recycle Co., Ltd, in Tokyo.

The products many of us purchase on a regular basis — the water bottles, clothes and, perhaps especially in the era of COVID, take-out containers from our local restaurants — are often plastic, disposable and bound to outlive us for generations. But the enormous amount of plastic waste that humans leave behind is a logistical and ecological nightmare, and experts say potential solutions must be approached from multiple angles, both for the planet’s sake and for our own.

Chemical engineer Paul Dauenhauer of the University of Minnesota has dedicated his career to revolutionizing the materials we rely on most. He’s worked to derive crucial “chemical building blocks” from renewable resources that can be used to manufacture existing products, as well as create entirely new alternatives.

Unlike materials like fallen leaves or animal waste, which decompose easily with help from microbes, the plastics we use today can’t break down as well. And they pose another environmental threat because of the way fossil fuels, whose derivatives are used to create many consumer products, including plastics, are extracted from the earth.

Dauenhauer, who was named a 2020 MacArthur fellow, has used biomass — like wood and plants — to engineer renewable chemicals that are essential to the production of widely-used materials from plastics to rubber-based products. Isoprene, for example, is a “monomer” chemical that can be strung together to create polymers like the substance used to make car tires. Dauenhauer has derived isoprene from biomass that’s considered a “drop-in replacement” because it’s identical to one that can also be derived from fossil fuels, and offers the exact same performance.

Swapping in these more sustainable alternatives can help reduce our reliance on oil and gas, the extraction of which is a major source of pollution with a hefty environmental impact.

But this work doesn’t stop with replacements. Dauenhauer and his colleagues are also invested in determining how to engineer materials so that they can biodegrade more quickly, be broken down and recycled multiple times or have more convenient properties than the ones we use today.

“There’s an opportunity here to not only solve environmental problems, but to create new, better products,” he said.

A primary challenge is making these alternatives both as useful and as cost-effective as the fossil fuel-based materials they seek to replace. That’s crucial, Dauenhauer emphasized, in order to capture the interest of both consumers and the companies responsible for manufacturing and selling our most-used products.

The only ideas for renewable materials “that are really going to have significant impact are the ones” that are cost competitive, Dauenhauer said. That marks the difference between technology that could have a meaningful impact on the world versus something that’s “more of just a scientific project,” he added.

Dauenhauer spoke to the PBS NewsHour about the major challenges we face when it comes to fully pivoting away from fossil fuels, and how he and his colleagues are working to engineer sustainable solutions that benefit consumers, manufacturers and our planet.

This interview has been condensed and edited for clarity.

You’ve characterized our unsustainable reliance on fossil fuels as “a race against time.” Can you describe what we’re up against here in terms of environmental impact?
The basis for the modern economy, a lot of it is energy and materials. And those come from fossil fuels like petroleum and natural gas. Think about the electricity that we use every day, but also fuels in our car and materials like plastic for clothing, cars, food packaging, metals, medical supplies. The problem is that they’re all contributing to environmental problems. And that could be climate change, of course, with CO2 emissions and methane emissions, but also plastic waste, which gets into the oceans, the rivers, the soil and our drinking water. And so all of these are a big problem that accumulate over time. And we need new technologies that can address this, essentially before they accumulate to the point where they’re disastrous.

The thing with fossil fuels is there’s an enormous supply. The problem is not that we’re going to run out of fossil fuels, it’s that we’re going to create too much of an environmental problem long before we would run out of fossil fuels. And so we need to actually find a way to transition and leave fossil fuels in the ground, which is difficult because the economics of fossil fuels are so low-cost that it’s hard to say, “We’re going to switch to something else.”

How does the carbon chain work now, and how is it being reimagined?
Society has the same approach for everything, whether it’s energy or materials. We take something from one place, we use it and then we throw it away someplace else. For fuels and energy, we take it out of the ground, we use it and the waste goes into the atmosphere. For plastic, it comes out of the ground, we use it and it goes into a landfill or it might go into the environment.

The idea of a circular economy, though, is that we take carbon from the same place we put it at the end of its life. So for recycling plastics, that means we trap it — maybe in your recycling bin — but that has enough value that we can reuse it. And so it just keeps going in a circle, and that carbon never goes anywhere.

Biomass fits into the closed cycle because all the carbon in it comes from the atmosphere. Let’s say you make a biofuel, for example. That carbon goes into the atmosphere, but then the next year, it pulls just as much carbon dioxide back into the ground — into the plant material itself. So it’s a net-zero emitter in that closed cycle.

People talk about pulling CO2 out of the air and then converting it into different things. Essentially, that is what a plant does. It’s really good at pulling CO2 out of the air by photosynthesis and capturing it — it’s a little CO2-capturing biological device. We don’t have to invent that, nature already invented it. We just have to figure out what to do with it once it’s in solid, plant-like form.

What are some of the main barriers when it comes to transitioning away from fossil fuels?
I think scaling up renewable, sustainable technology cost effectively is the No. 1 challenge. I mean, the benefits of electricity and power and materials are just too great, right? They give an enormously high quality of life. Nobody wants to go back to an age where we don’t have access to these things, nor should we. They have a huge benefit for humanity. But to replace them with something sustainable, we have to do that in a way that doesn’t change the cost dramatically or or even at all. And that’s really the challenge.

There are just thousands of ideas out there for renewable materials and sustainable electricity. But the only ones that are really going to have a significant impact are the ones that can be engineered in a way that they’re cost competitive. We use that as the benchmark for [answering questions like] Is this technology actually going to have impact or is it more of just a scientific project?

What is catalysis, and why is it so important to your research?
Catalysis is a technology that lets you turn one molecule into another. It’s a very old field, over 100 years old. And we use things like metals and metal oxides and other solid particles — frequently nanoparticles — that allow the molecules to stick to a surface and then convert. And we design the surface such that the molecules convert the way we want. So it fits into this idea of the bio economy and the circular economy by finding the chemistries and process technology that let us do this most efficiently.

So I start with a plant, and about two-thirds of plants are actually sugars. So cellulose and hemicellulose are two of the biggest components of plants, lignin being the third one. But I can pull that out and make sugars out of it. And once I have it as a sugar, I can put it in water and it dissolves. And so from there, I can do the chemistry using our catalysts. And once I make a molecule from the sugar, that would be used to make a material that’s called a monomer.

Now, those monomers that I make, a polymer researcher will take those and link them together like beads on a chain — like a pearl necklace, conceptually. And then once he gets that big molecule, that becomes the solid polymer. And that’s the material that people use. So I work on the part of making the monomer. And for some of these materials, once we have the monomer, we know how to make existing materials. For new monomers and new polymers, I partner with people that do polymer chemistry and they design the new materials from the chemicals I make.

Does the approach of engineering drop-in replacements versus creating entirely new materials have more merit than the other?
It’s going to be a mix of both. Some of the key polymers and plastics we use right now, [two big ones being] polyethylene and polypropylene, are really, really cheap to get, and they have very good properties for what we use them for. There’s no way in 100 years we’re not going to be using those materials. So for that application, we need to find a way to use it at the end of its life and keep it out of the environment.

For other applications, like maybe for clothing, we can find new polymers. Those are places where designing the molecules could make better properties that maybe make the fabric softer or more comfortable than conventional polyester. So I think it’s gonna be a mix of both. No one solution is going to work for everything.

If you look at anything as a renewable recycling logo No. 1, that’s P.E.T. plastic, that’s a polyester. And we use that all sorts of places for clothing, for soda bottles, for car parts — it has really great properties. And so we can make that renewably, but it’ll still have the same issues of what we do with it at the end of its life. What we need is not just the ability to make new materials, but also something to do with them after we’re done with them. Can we recycle them in a way that keeps their properties just as good, even if we’ve used them 50 times or 100 times or a 1,000 times?

I’m from Minnesota, and so the one thing I care about in winter is, do the [plastics we use] get brittle in winter? There is an opportunity to make better materials that have better properties and that’s one of them, that they don’t crack or break during the winter, but they’re also recyclable or biodegradable or both.

Isoprene is a common compound used in the production rubber that’s typically derived from fossil fuels, but you’ve been able to derive it from biomass. Is that isoprene identical to the kind that’s made from fossil fuels?
Isoprene is a drop-in replacement. So you could buy isoprene that’s made from fossil fuels or you could buy isoprene that’s made from a renewable process and you wouldn’t know the difference unless somebody told you. It’s a very specific molecule. So that, in theory, would let you make the exact same product you get right now. You could buy a car tire made from renewable isoprene or fossil-derived isoprene, and it would be the same tire.

So even if chemical replacements like isoprene are sustainably derived, can they still create the same environmental issues as the chemicals they’re replacing?
Making something renewably derived doesn’t solve all the problems if there are other problems with the product. Like car tires, what do you do with a car tire at the end of its life? If you source the exact same chemicals renewably, it only solves part of the problem, which is the sourcing. It doesn’t solve the end-of-life problem. If some chemicals have environmental problems, sourcing them renewably — if it’s the exact same chemical — will still have the same problem. So there are cases where you would like to have a new polymer entirely. And there are cases where that’s probably not going to be feasible and we need to find another solution, like car tires. We need to find an end-of-life technology for that because the current performance is basically a safety issue. You don’t want to change the performance of the car tire.

Is it possible to engineer products that use chemicals derived from biomass in a way that could make them more sustainable?
Let’s say we make the same molecules from biomass that we use right now. You could still restructure the polymers in a slightly different way or add in other components that help them break apart. I’m part of the Center for Sustainable Polymers where I work on the feedstock side. But other people work on redesigning the polymers in a way that makes them maybe more recyclable, or more biodegradable, or both, using the existing materials we have right now. So is it possible to make a car tire that could be easier to use at the end of life without changing its performance? Could you make food packaging keep its really good barrier properties that keep your food fresh but also make it biodegradable, and not a significant difference so that the consumer doesn’t doesn’t mind it?

We’re trying to find the lowest economic barriers to find sustainable solutions. And replacing entire polymer generations and technologies is not economically viable. So are there other ways to kind of hack these technologies and build in sustainability in a way that doesn’t require a complete revamp? Absolutely. And because we’re a center, we’re a lot of people working together. We’re sort of technology agnostic. If it’s a new material entirely or if it’s a modification of an existing material, both of those are a fair solution to the problem.