Researchers in Worcester Polytechnic Institute's Department of Chemical Engineering and at The University of Akron have published research in Chemical Engineering Journal about a new technology that seeks to solve long-standing challenges in plastic recycling that limit the overwhelming majority of plastics to a single use and contribute to the accumulation of plastic waste.
The problem
Currently, less than 20% of all plastics are recycled. Increasing that number will require solving several problems, including irreversible loss of properties during the recycling process, limited ability to blend plastic mixtures, discoloration, and carryover of toxic chemicals.
Current approaches
Mechanical recycling, which involves physically sorting materials and reprocessing them into materials for new production, is plagued by the aforementioned challenges. One proposed solution to these problems is chemical recycling, which uses heat and catalysts to break down plastics into substances that can be refined to become fuels or processed further for petrochemical production. Unfortunately, chemical recycling in its present form is energy intensive and costly, requiring both breakdown of plastics and the rebuilding of broken chemical bonds.
The new study
A team of researchers from Worcester Polytechnic Institute's Department of Chemical Engineering and The University of Akron partnered with the startup Seauciel to study a third approach proposed by the company, which it calls "aqueous chemi-mechanical recycling." The process relies on properties of water heated beyond its normal boiling point to convert polymers found in plastics into a state at which they can blend with each other at the microscale. Tests of this approach show evidence of microscale mixing after the chemi-mechanical treatment.
Additionally, the research study found chemi-mechanical treatment resulted in 96% reduction of the volatile organic compounds that are partially responsible for "recycled plastic smell" compared with plastics processed using mechanical recycling. In addition, chemi-mechanical recycling removes pigments from polymers to restore recycled material closer to the color of virgin plastic. The researchers found that carefully controlling the amount of time materials are exposed to the high temperatures in this treatment process minimized molecular weight loss of the polymers during processing—a major drawback of mechanical recycling—and used much less energy than chemical recycling.
The research team also reported that the process can deliver recycled plastics at a price similar to virgin-made and has a carbon footprint comparable to mechanical recycling and far smaller than incineration.
The next steps
The team's future work is expected to include scaling the technology while conducting further research to provide a robust physical understanding of the key phenomena. "With continued progress, this new technology could ultimately make single-use plastics a thing of the past," said Michael Timko , William B. Smith Professor of Chemical Engineering and head of the Department of Chemical Engineering at Worcester Polytechnic Institute and one of the authors of the report. "Large quantities of plastics are disposed of in landfills or enter the ocean, causing environmental damage and representing lost potential for material reuse and energy capture."
Additional authors on the report include:
Madison Reed, PhD '25, Department of Chemical Engineering, Worcester Polytechnic Institute
James M. Eagan, assistant professor, The University of Akron
Abhishek Banerjee, PhD '24, The University of Akron
Arsalaan Nisan Pathan, PhD '25, The University of Akron
