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Plastics are a problem. They are made with petroleum, are rarely recycled, and turn into microplastics over time—an increasingly intractable global environmental and health concern.��

Current bio-based alternatives have yet to see widespread adoption for a number of reasons. Carson Bruns, associate professor (ATLAS Institute, Mechanical Engineering), aims to change all that with a new line of research in his��Emergent Nanotechnology Lab focused on turning agricultural materials into bio-based plastics that can be more easily recycled, composted or even used as fertilizer.

Bruns was recently awarded a��2025 Research & Innovation Seed Grant from CU 51��ý’s Research and Innovation Office for this work.��

We discussed the thinking behind this research and possible applications (interview lightly edited for clarity):��

What are the challenges with bio-based plastics?

The biggest challenge that everybody is dealing with in sustainable plastics right now is that the current options for bio-based and compostable plastics are not actually very good. They don't compete with the oil-based plastics in terms of how tough and flexible they are, so people don't like to use them as much because they crack and they're brittle.

And in reality, you cannot throw such plastics onto your backyard compost pile. They need special conditions to properly break down. You need a composting facility that heats the compost up to 60°C and it has all these fans and equipment to circulate it, and even then, it still doesn't work that well. [Note: This is one of the reasons why A1 Organics, 51��ý, Colorado’s main composting partner, stopped accepting these biodegradable plastics.]

Bruns and his team have partnered with��Merritt R. Turetsky, Director of Arctic Security; Professor, Ecology, for key elements of this research.

How did the collaboration with professor Turetsky come about?

We've been working on sustainable alternative materials to oil-based plastics for almost the whole time I've been at CU. But the collaboration with Professor Turetsky came when we started trying to characterize the biodegradability of the materials we've been making in the lab.��

We've worked with a number of different things—rubbery materials, hydrogels, elastomers, and adhesives [as] alternatives to oil-based rubbers and adhesives. If you want to characterize how biodegradable something is, there are different types of experiments you can do. We approached professor Turetsky to get her advice on how we could go about doing that.

Over the last two semesters, we've had an undergraduate student named Roan Gerrald. He did his honors thesis on this work with advice from professor Turetsky and��Aseem Visal, my graduate student. He's done our first compostability experiments on some of the plastic alternative materials that we've already made that are not the ones we proposed in this project, but ones that we have in the lab.

Carson Bruns

What materials are you testing to make these new polymers?

The recipe is [a key] innovation. In general, what you do when you're trying to make a sustainable plastic is you buy some very high-purity materials from a chemical supplier and that makes your science easy to do because you know exactly what you have.

Just buying this molecule in a gallon drum is economically not at all competitive with petroleum. So how do we make something that is cost-competitive?��

The idea is to try to recover these molecules as starting materials from waste so that they're not so expensive. You're a potato chip or french fry manufacturer, and you have to wash all of your vegetables, or even at intermediate stages you're soaking them in water or washing them with water, and then that water waste goes somewhere. But it has valuable stuff in it like starches and proteins from the vegetables. So we'd like to recover those valuable substances from the wastewater.

You're using these different materials that happen to be fertilizers in themselves.

The problem with using carbon for plastic is that even if it is highly recyclable, even if it is compostable, It's still going to turn into carbon dioxide at the end of its life.

We choose elements that plants need so that we avoid the carbon but still maintain compostability or biodegradability. But we can't get rid of the carbon completely—it's more of a carbon minimization than a carbon avoidance or removal in order for it to still behave as a plastic and have that kind of flexibility.

So if we can make a plastic that has not very much carbon, but it has a lot of other stuff that is good for soil, then you can use it as a fertilizer instead of as compost, because agricultural fertilizer doesn't have carbon in it—it has nitrogen and phosphorus and potassium and sulfur and things like that. So let's make our plastics out of that stuff, so that we don't have carbon in the air at the end.

What do you hope to accomplish at the end of the initial 18-month grant?

I hope that we have at least one material that has good properties and that we show fertilizes soil. That's a very ambitious goal to have in 18 months, but we're going to try.

What sorts of products might be possible with this plastic alternative?

We want to make packaging plastics, something that you could cover your steak with at the grocery store or something like Styrofoam. But these are soft and flexible, and because of that they're a little bit harder to make from these low-carbon elements.��

So I would predict that it will be harder for us to make those things, but if we can make the kind of flexible, more stretchy ones, then we can look to things like packaging, plastic bags, Ziploc bags, Saran Wrap, stuff like that. But if we can [only make] brittle things, then it's gonna be more like forks and cups and plates.

How might this research come to life in the real world?

Maybe in the future if it worked really well, there could be a reuse or recycling stream where you put it in your mixed-stream recycling and then they sort it and send it to somebody who is going to turn it into fertilizer.��

But the other option is that you throw it in your at-home compost and it can degrade there and that would be great, too.