The Trienens Institute Store Pillar
Jan 15, 2025 10:43 AM
One of the Trienens Institute Six Pillars of Decarbonization, the Store pillar aims to facilitate the large-scale deployment of renewable energy sources in the energy grid
The Trienens Institute Recycle Pillar
Giving new life to plastic
Julianne Beck | January 27, 2025
Over the course of a century, a discarded mattress could slowly decompose in a landfill, or it could be upcycled for use in new mattresses. It is the latter vision that drives the work of Northwestern researchers who are focused on solving the plastic pollution crisis.
Demand is skyrocketing for all forms of plastic, from a candy box to the tires on a car. In one year, 100 pounds of plastic are produced per person on the planet. That’s 800 billion pounds total. Yet less than 10% of plastic waste is recycled.
“It’s a sizeable issue and almost all of that ends up going into the waste stream or ends up lost in the environment,” explained John Torkelson, Walter P. Murphy Professor of Chemical and Biological Engineering and Materials Science and Engineering.
In addition, the vast majority of plastic items are currently derived from fossil fuels. To create new plastic, those fossil fuels go through energy-intensive processes to refine the chemicals that are transitioned into plastic. Those processes release carbon dioxide (CO2) into the atmosphere.
As part of the Paula M. Trienens Institute Recycle pillar, Northwestern is leading the creation of advanced polymers and processing methods for materials that will help solve the plastics pollution crisis and create a viable circular economic model at scale. The pillar is one of Trienens Institute's Six Pillars of Decarbonization aimed at leading interdisciplinary research in decarbonization.
Torkelson serves as co-chair of the Recycle pillar alongside William Dichtel, the Robert L. Letsinger Professor of Chemistry.
“We will all benefit from collectively doing this better,” said Dichtel. “Every human on this planet will benefit from plastic ultimately transforming to a more circular and sustainable use.”
Through the Recycle pillar, they aim to develop ways to recycle both CO2 and existing plastic materials into new plastic products over-and-over again.
Northwestern has a longstanding history of research in the field that extends back nearly a half-century. “We have a lot of great people in departments that might be central to these issues in terms of chemical engineering, chemistry, materials science, and engineering,” said Torkelson. “The researchers have come with somewhat different backgrounds and are experts who have interest in these topics.”
As the field picks up steam with growing awareness and interest, research is accelerating.
“There’s a culture of innovation here. This is a great place to be working on these kinds of projects…The successes are happening right now,” said Dichtel.
Breaking Down Plastic
All plastic is not equal. There are two main classes, thermoplastic and thermosets, which are then further categorized based on their chemical composition. They cannot be mixed when recycled, unlike materials such as glass or aluminum.
Single use grocery bags and water bottles are made of the most common class of plastic, called thermoplastic. They are built with chemical structures that allow flow at high temperatures and remolding into new products. However, there are limits to how many times they can be recycled before they degrade and become unusable.
In Torkelson’s laboratory, research into upcycling some of the most common types of thermoplastic has been developing. “We can take materials that are not valuable and actually upcycle them for reuse in a way that is actually of higher value,” said Torkelson. In particular, “we have been successful in terms of upcycling things like polyethylene and polypropylene,” two of the most common types of thermoplastic, into cross-linked network materials that in the past would have been called thermosets and could not be reprocessed. “We found ways to reprocess these multiple times and it’s just a one-step process.” Partnership is critical to scaling up such discoveries for real-world applications. Torkelson’s collaboration with DOW, a materials science company, has supported this work. “We’ve been able to do things with materials now that people thought were just hopeless,” said Torkelson.
Mattresses, insulation, and upholstery often include the other class of plastics, called thermosets. This class of plastic has more complex structures that were designed to endure indefinitely. A large subset of thermosets is called polyurethane’s—a category of great interest to Northwestern researchers.
“We have been working on recycling plastics that were never designed to be recycled at all,” said Dichtel, who’s successes in recent years have included the discovery of a catalyst to recycle polyurethane, followed by his discovery of a process to recycle polyurethane foam directly back into polyurethane foam for new uses. “We’ve been working on this problem for several years, and over the course of that time we’ve taken more and more steps toward it being practical.”
Dichtel and his team partner with BASF, an international chemical company, to continue to build these processes. Looking forward, “we actually see ways to take waste foam materials and use that as a starting material that could filter into many different products,” said Dichtel.
Additional discoveries have emerged at Northwestern, including a catalyst to recycle fishing nets and other items made from nylon-6, a common and durable thermoplastic, by Tobin Marks, Vladimir N. Ipatieff Professor of Catalytic Chemistry and Chemical and Biological Engineering.
Across the board, energy is saved when plastic is recycled as compared to producing new plastic, while fewer items wind up in landfills and circulate through the environment as microplastics. In the future, “the ultimate societal metric here will be what percentage of plastics are taken back through a cycle that is not landfilling or incinerating,” said Dichtel.
Rebuilding Plastic
An emerging area of research involves using carbon dioxide as a feedstock for new forms of plastic. “What we want to do is to find a way to reduce or control the level of CO2, and if you can put it into a useful material that is not then going to return that into the atmosphere for a long time, you can contribute to a solution to the [climate] problem,” said Torkelson, who believes solutions from all corners can come together to make a significant difference when it comes to the climate.
The work of this pillar integrates with the other Trienens Institute Pillars of Decarbonization. “All of these pillars are the major societal challenges that we need to advance so that our modern lives can be less carbon centric,” explained Dichtel. “It’s the materials that we use, it’s the energy that we generate, it’s connected to water, it’s connected to food, it’s across all of modern society—how we can make what we need and how do we live our lives in the most sustainable way possible.”