Innovative plastic waste recycling process converts polyethylene and polypropylene into chemical building blocks, enabling a circular economy

Scientists at the University of California, Berkeley, have developed an innovative chemical process that can effectively convert plastic waste into valuable chemical building blocks for the production of new plastic products. This catalytic process enables the breakdown of dominant types of plastic in waste—polyethylene and polypropylene—into their basic chemical components, significantly bringing us closer to a circular economy for plastics.

The process uses two key catalysts: sodium on alumina and tungsten oxide on silica. The first catalyst breaks down the polymers, leaving one end with a reactive double bond, while the second catalyst uses this bond to add carbon and create a propylene molecule. Propylene is one of the basic ingredients for producing new polymers, allowing the reuse of plastic waste without the need for new fossil fuels.

This new process offers numerous advantages over previous methods. First and foremost, it eliminates the need for complex and expensive catalysts that were used in earlier research. Replacing these catalysts with cheaper, solid catalysts allows for a continuous process, meaning the catalysts can be reused, reducing costs and increasing efficiency. This technology also avoids the need for hydrogen removal to form a double bond in polymers, which was a key step in earlier plastic degradation methods.

Applying this method could have a significant impact on reducing global plastic waste, which today largely ends up in landfills, oceans, or is incinerated, further contributing to greenhouse gas emissions. According to estimates, about two-thirds of post-consumer plastic waste consists of polyethylene and polypropylene, and most of this waste is currently recycled into low-value products such as flower pots and plastic cutlery.

One of the key innovations of this process is its ability to break down plastic at the molecular level, allowing for the production of products of the same quality as those made from new, unused material. This process potentially enables the production of new plastic products without compromising quality, which is a crucial step toward a more sustainable approach to plastic waste management.

Additionally, the new method is significantly more resistant to contaminants that could reduce the efficiency of degradation. While small amounts of impurities such as PET and PVC can reduce efficiency, most impurities have no significant impact, meaning the process can operate effectively even with less clean plastic waste. This is crucial for the commercialization and broader application of the technology.

Scientists believe that this technology could lead to the creation of commercial plants for breaking down plastic into building blocks for new materials, which could significantly reduce reliance on fossil fuels and the amount of plastic that ends up in the environment.

This project was funded by the U.S. Department of Energy, and the research results will be published in the scientific journal Science. Along with Professor John Hartwig, who led the research, the work involved doctoral students Richard J. Conk, Jules Stahler, Jake Shi, Natalie Lefton, and John Brunn, as well as researchers from Lawrence Berkeley National Laboratory.