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Plastic Fest event art
June 22, 2021

The future of recycling involves elephant toothpaste, Skittles and a few smart kids

Written By: Jason Daley

Skittles and mini-marshmallows are not typical laboratory supplies (well, maybe in the lab’s break room). But in April 2021, the treats, along with dry yeast, rubbing alcohol, egg cartons and other household items were the primary equipment for a group of would-be young scientists scattered across Kenosha, Milwaukee, Racine, and Waukesha counties in Wisconsin.

The kitchen-table labs were set up for the virtual Plastic Fest, a 4-H event co-hosted by the Center for Upcycling of Waste Plastic (CUWP), a multi-university research center at the University of Wisconsin-Madison led by George Huber, the Richard L. Antoine Professor in chemical and biological engineering.

The program, which included two hour-long sessions held on two different nights, was designed to introduce the young chemists to some of the emerging concepts behind plastic recycling.

While many people believe that most plastic can be recycled and reused, that is not the case. Only about 9 percent of plastic—even the stuff tossed in the recycling bin—is reused. And even most of that is downcycled into lower-value products. The reason is that plastics can only undergo mechanical recycling a small number of times before they are discarded as the heat and shear of processing conditions cause plastic degradation.

Due to this limitation, the CUWP supports research into chemical methods of recycling plastic, like pyrolysis, in which plastic is broken down into smaller chemicals by melting it in a low-oxygen environment, and solvent-based processing, which can separate multilayer plastics into its original polymers. Those polymers can be reused over and over again without any loss in quality, similar to the way aluminum cans are endlessly recycled.

“I think this research is really accessible for the public, because recycling is something they should be doing every day,” says CUWP education director Andrew Greenberg, a distinguished faculty associate in chemical and biological engineering. “We want the public to gain a better understanding of what gets recycled in Wisconsin and what doesn’t, why it’s recycled and why it’s not, and how researchers are working on solving these issues.”

 Edgard Lebrón-Rodríguez
Edgard Lebrón-Rodríguez

To demonstrate these concepts to younger people, Greenberg made chemical recycling the focus of his one-credit course, Chemical Engineering in the Community, for the 2021 spring semester. In the course, undergraduate and graduate students develop presentations to explain chemical engineering research topics to elementary and middle school students, and the engineers typically give their talks in public at least twice.

In spring 2021, with COVID restrictions still in place, the class met virtually with the goal of giving presentations online for the 4-H event and during an Earth Week celebration sponsored by the local chapter of the American Chemical Society and the Institute for Chemical Education.

One class participant developed a module discussing upcycling, asking the younger students to create new, creative products out of used plastic bottles, CDs, egg cartoons and other items considered trash. Another led students in an exercise to learn about solvents, directing an experiment where the young learners used rubbing alcohol to strip the candy coating off Skittles. The demonstration led to a discussion of STRAP processing, a new solvent-based technique pioneered at UW-Madison that uses solvents to separate multilayer plastics.

Chemical and biological engineering graduate student Edgard Lebrón-Rodríguez created an activity to teach catalysis, which is an important part of accelerating and improving the formation of desired products of chemical recycling processes. Catalysis happens to be the subject of his research.

As an undergraduate in Puerto Rico, Lebrón-Rodríguez participated in several science-based community outreach projects, which he enjoyed. He signed up for the class hoping that practicing communication with younger people would help him become a better mentor, not only to undergraduates in his research group, but also to students attending the UW-Madison Research Experience for Undergraduates program, which he will help lead virtually in summer 2021.

To explain what catalysts are to the 4-H kids, Lebrón-Rodríguez had the students conduct the classic “elephant toothpaste” science experiment, in which dry yeast (the catalyst) added to hydrogen peroxide accelerates its decomposition and creates a massive flood of foam. “It’s a fun and colorful way to show what a catalyst does and gets the students engaged quickly. That’s why I chose it,” he says. “I tried to be open and spark creativity. Together, we would form a hypothesis—like would adding more catalyst make the process faster—then check our results just like a scientist or engineer would.”

During his first presentation, he says he tried to go slow and keep things concise to get the main message across. “It’s a balancing act,” he says. “There’s always a battle between making a presentation longer with more information and the kids getting bored or making the presentation too short and not sparking any creativity or curiosity.”

The second time around, he adjusted his presentation, asking the kids more questions to keep them engaged, curious and more focused on the “fun part,” which also included a lesson in making porous catalysts and molecules out of toothpicks and marshmallows.

Lebrón-Rodríguez explained that catalysts used in industrial processes are usually powders (solids) and chemical plastic processing in particular benefits greatly from porous aluminosilicate materials such as zeolites. “The size of the pores and the acidity emanating from the presence of aluminum allow it to break plastic into smaller chemicals like pyrolysis but with the added benefit of being able control what type of products are formed,” he says.

For the activity, students designed a porous catalysts out of toothpicks and marshmallows by changing catalyst pore size and active sites, which is what Lebrón-Rodríguez does through zeolite synthesis for his research.

Greenberg says ideally the course and presentations will provide a spark of interest to the kids to look more deeply into chemical engineering and recycling. He also hopes the course has benefits for the student presenters. “We want to give students the opportunity to practice their nontechnical communication skills and think about how to present really technical information to people without a technical background,” he says. “That can be especially valuable for undergraduate students moving into professional engineering careers, where they are going to have to work with and explain things to people from nontechnical backgrounds.”