A diverse scientific team from government, academia, and industry collaborate to identify new ways to reduce the environmental impact of polyurethane, one of the most widely used but little recycled plastic materials.
Polyurethane is one of the most widely used plastic materials in the world, but it is frequently overlooked in our daily lives. However, whether you’re at home, at work, or in your car, it’s never far away, with common end uses ranging from mattresses and furniture cushioning to building insulation, car parts, and even shoe soles.
However, as with other plastics that are largely unrecycled, polyurethane’s widespread use is raising concerns about its environmental impact. Researchers from the U.S. Department of Energy’s (DOE) Argonne National Laboratory, Northwestern University, and The Dow Chemical Company collaborated to conduct the first comprehensive assessment of “Material Flows of Polyurethane in the United States” to better understand the opportunities for recovering polyurethane for recycling and replacing the chemicals used in its production with plant-based alternatives. The findings were published recently in the journal Environmental Science & Technology.
Plastics are extremely useful and have numerous societal benefits. If we got rid of plastics, we’d have to deal with a slew of other issues that could end up causing more environmental damage than the plastics themselves. As a result, we must continue to look for ways to intervene in the current system and improve things.
Jennifer Dunn
“The goal was to understand how linear versus circular our use of polyurethanes is in the United States,” said co-author Jennifer Dunn, associate director of Northwestern’s Center for Engineering Sustainability and Resilience and a member of the Institute for Sustainability and Energy’s Program on Plastics, Ecosystems, and Public Health (ISEN). “We also wanted to see if there are opportunities to enhance circularity and increase the bio-based content of polyurethanes.”
A linear economy is one in which raw materials are used to manufacture products that are then typically discarded at the end of their lives. Those same materials are recovered and reused in a circular economy. This reduces the need to extract additional natural resources, such as fossil fuels, while also reducing waste sent to landfills.
Dunn, an associate professor of chemical and biological engineering at Northwestern’s McCormick School of Engineering, said that while researchers expected to find a large linear system for polyurethanes, “from the starting materials to the end of life, it was just blatantly linear.”
According to co-author Troy Hawkins, who leads the Fuels and Products Group in Argonne’s Systems Assessment Center, the study highlighted a number of complexities that affect how and when polyurethanes can be recovered and recycled.
“Polyurethanes come in a variety of forms, from rigid to flexible, and each of these applications looks and acts differently. Polyurethane use has grown rapidly over the last 50 years, and many applications are long-lasting. So what is going in now may not be used for another 10, 20, or 30 years. In addition, there is a problem with the concentration of polyurethane in various applications. For example, an adhesive or sealant is much more difficult to separate and recover than a mattress or carpet padding” he stated.
Furthermore, polyurethane supply chains have long been known to involve toxic materials known as diisocyanates, and the study identified how and where they are used. “Having this complete picture allows us to see opportunities for recovering and recycling polyurethane, as well as replacing some of the polyurethane production inputs that have environmental and safety concerns with safer, low carbon bio-based chemicals for the first time,” Hawkins said.
The involvement of Dow was one of the study’s distinguishing features, according to Dunn, because it allowed the researchers to incorporate detailed data and technical insight based on actual industry practices.
“Dow was an important part of this research. The Dow co-authors’ experience grounded the analysis in real-world knowledge of how polyurethanes are made and used “She stated. “They’re also keen on increasing the circularity of their systems and remaining at the forefront of best practices for incorporating cleaner materials.”
Hawkins stated that there was also a strong collaboration between Argonne and Northwestern, with each bringing a wide range of capabilities and resources that had been built up over time. “It really provided synergies and an opportunity that we would not have had individually,” he said. “It also allowed us to include new elements that we don’t normally track in life cycle assessments.”
It took about a year to complete the project. It was sponsored by the DOE Bioenergy Technologies Office within the Office of Energy Efficiency and Renewable Energy and managed by ISEN as part of a three-year collaborative initiative called Responsible Innovation for Highly Recyclable Plastics.
Dunn stated that the team would use the findings to help guide the development of new chemistries that could lead to more recyclable, bio-based polyurethanes in the future. “If we want to design a circular economy, we and other researchers will need to keep contributing to this body of knowledge about these supply chains,” she said. “We need to understand the current state of affairs if we’re going to develop cost-effective technologies and produce recycled plastic materials that perform as well as or better than what we’re used to.”
Hawkins added that the ultimate goal is not to eliminate plastics, but rather to ensure that they are used responsibly and sustainably. “Plastics are extremely useful and have numerous societal benefits. If we got rid of plastics, we’d have to deal with a slew of other issues that could end up causing more environmental damage than the plastics themselves” he stated. “As a result, we must continue to look for ways to intervene in the current system and improve things.”
