Beyond bottles: Addressing the Challenge of Forgotten Plastics

By Mary Hoff

From brushing our teeth first thing in the morning to putting our head on the pillow at night, plastics are part of pretty much everything we do. They not only make life more pleasant, in some cases, they literally keep us alive. But they also have serious downsides. For one thing, they’re made from fossil fuels, which contribute to climate change. And their durability means they pollute land, water, and—in minute quantities—even the insides of our bodies.

Efforts to address the plastics problem often focus on everyday plastic objects such as bottles and bags. But plastics also permeate our lives in more subtle ways. Three MnDRIVE seed grant projects are working to solve challenges related to less conspicuous plastics—two in partnership with companies looking for ways to use plastics more responsibly.

Sticky Problem

In his previous job with a water treatment company that worked with paper recycling plants, Steve Severtson became aware of a sticky problem: pressure-sensitive adhesives like those used on envelopes and postage stamps were notorious for gumming up mixed office waste recycling. Part of his job was to look at ways to undo the damage in preparation for making recycled paper—an important task, with the market for the adhesives growing 5 percent per year. But then he thought, “Why not move upstream and work with adhesive companies to solve the problem before it occurs?”

Today, Severtson, a professor of bioproducts and biosystems engineering, is working to do just that. He’s developing adhesive polymers that function like—and are partly made of—traditional adhesives but include bio-based materials. As part of that effort, he’s interested in figuring out ways to break them down when their useful life is over, so they avoid sullying the environment and recycling equipment. 

Fortunately, as part of an interdisciplinary department, Severtson is office neighbors with Jiwei Zhang, a geneticist with his finger on the pulse of fungi—the world’s preeminent biodegraders. He also happens to have a former colleague, Mike Nowak, who now works at H.B. Fuller. Bringing all of the pieces together, he and Zhang received a MnDRIVE seed grant to explore strategies for biodegrading adhesives.

Led by Jesus Castano, a postdoc in Zhang’s lab, the research team is using the MnDRIVE grant to assess the ability of various fungi to break down bio-based adhesives Severtson is developing. H.B. Fuller is providing in-kind support.

“We have found some interesting strains that degrade the adhesives we are studying,” Castano says. The next step: taking a closer look at how the sticky stuff disintegrates and testing the various candidates’ performance in a natural environment.

“Our hope is that ultimately, over two to three years, we have something that’s commercializable, that’s going to impact the industry,” Severtson says. “We’ve had some pretty good results so far. We’ll see how this goes.”

Corralling Microplastics

Everywhere we look, we see plastics. It turns out they’re pretty much everywhere we can’t look, too. Microscopic bits of plastic, many worn from larger objects and carried long distances by wind and water, have been found in beverages, food, even ice above the Arctic Circle. Threats to the health of humans and other living things are unknown but likely.

Partnering with the sportswear manufacturer Adidas and civil, environmental, and geo-engineering assistant professor Boya Xiong, mechanical engineering associate professor Cari Dutcher and graduate student Vishal Panwar are looking for an environmentally friendly way to capture microplastics from wastewater and water being treated for human consumption. Their goal: to identify biologically sustainable substances that attract and combine with microplastics the way a magnet attracts iron filings. 

Flocculants like synthetic polymers have long been used to remove larger contaminant particles from water destined for our taps. But conventional flocculants can break down in the environment into harmful chemicals that would also require treatment for removal. Dutcher and Panwar are exploring the use of a naturally abundant protein found in seeds of Moringa oleifera (drumstick tree) extracted by the Boya Xiong group for flocculating microplastics. Specifically, they’re looking at how much microplastic the protein can capture, how quickly the flocs can grow, and how durable they are over time.

In preliminary studies, Panwar has found that the crude extracts and purified protein from seeds can indeed capture microparticles made of polystyrene and polyethylene, plastics commonly used for packaging and disposable tableware. The next step is to test this on a larger scale in the laboratory using samples Adidas provides.

“Success for me would look like if we can prove that the biopolymers can have a better efficiency in removing these microplastics than the traditional biopolymer,” Panwar says. Eventually, the goal would be to use environmentally benign substitutes in water treatment systems, where they can remove microplastics without themselves becoming a contamination issue while also matching the efficiency of conventional synthetic polymers.

A Chip off the Old Rink

Enjoying an early-season visit to a Twin Cities lake last spring, Merck Professor of Chemistry Lee Penn was dismayed to see the bottom littered with paint chips from a hockey rink that provided winter recreation just a few months earlier. The scene made Penn realize that paint, which often contains plastics, could be a source of microplastics in lakes and streams. That’s a problem not only because microplastics themselves can move into fish and other organisms that live in surface waters—and even into you and me if they serve as a source of drinking water—but also because the microplastics can absorb other harmful contaminants and bring them along for the ride.

With the help of a MnDRIVE seed grant, Penn, graduate student Ari Companaro, and an undergraduate will dig into the potential of paint to contribute microplastics pollution to Minnesota waterways. Part of the exploration will involve looking at the paints used on objects such as hockey rinks, boats, and docks that could shed chips into waterways. Next, they’ll investigate whether the paints contain plastics. If they do, they’ll explore whether and how the plastics interact with titanium dioxide, a chemical that’s often used to whiten and brighten paint.

“Titanium dioxide can act as a catalyst for reactions that result in the degradation of organics, plastic materials, and so on,” Penn says. “That’s potentially a good thing with respect to microplastics, but we also have to think about the impact of that titanium dioxide on the environment. It’s definitely a complicated scenario.”

Though the threat from microplastics in paints pales in scale compared with that from other sources such as single-use bottles, Penn hopes the research will provide insights that might be used to better understand the role paint plays in the microplastics problem—and what we might do about it.

“It’s like soap,” Penn says. “When we started to learn that triclosan is a problematic molecule, we said, ‘Wash your hands, but not with triclosan.’ We might say, ‘Paint your boat, but with these kinds of products, not these.”

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