Recycling Breakthrough Set to Transform the Plastic Waste Landscape

By David J. CrossAug 17 2023Reviewed by Bethan Davies

Since the 1950s, humans have produced around 8.3 billion tons of plastic waste, which has had a colossal impact on the planet, with only around 9% of all plastic waste being recycled globally.¹

Image Credit: University of Wisconsin-Madison (UW-Maddison)

Plastic waste continues to accumulate and can be found almost anywhere on earth, across all six continents and in the oceans, from the highest mountain to the deepest marine trench; plastic waste has even infiltrated the food chain as microplastics have recently been detected in the human body.

To combat this, researchers at the University of Wisconsin-Madison (UW-Maddison) have developed a method that can convert low-value plastic waste into high-value chemicals. The team believes this method could have a transformative effect on the plastic waste landscape.

Published in the journal Science, the team describes the homogenous hydroformylation catalysis process, which recovers compounds known as olefins, the building blocks of most polymers in use today. The projections made by the team suggest that this method could lower greenhouse gases by up to 60% compared to conventional production methods for high-value oxygenated chemicals.²

We’re really excited about the implications of this technology… It’s a platform technology to upgrade plastic waste using hydroformylation chemistry.

Professor George Huber, Director of the Department of Energy-funded Center for the Chemical Upcycling of Waste Plastics

The Challenge of Plastic Recycling

Despite the implementation of certain mitigation strategies, such as new recycling methods and the ban on single-use plastics in 120 countries, the plastic problem continues to mount. The amount of plastic in the environment is verging on catastrophic, with much of it ending up in landfill. There is now estimated to be between 75  to 199 million tons of plastic waste in global seas and oceans and an additional 109 million tons in rivers.¹

Current methods used for recycling and converting single-use plastics into reusable materials and compounds are marred by high costs and sustainability issues. In order to extract olefins from pyrolysis oils, energy-intensive processes such as steam cracking require extreme heat and temperatures to be effective.

Around 85% of low-value plastic waste in the US is sent off to landfill sites, with only 5-6% of all municipal waste being recycled at all. This is despite an increase in domestic recycling methods. The US also ships off large volumes of plastic waste to other countries. Despite all of this, low-value plastic products such as food packaging, grocery bags, plastic straws and stirrers, and PET bottles still litter the country’s landscape.³

Pioneering Hydroformylation Catalysis

The homogenous hydroformylation catalysis method developed by the UW-Maddison team was a collaborative effort as Huber brought in the expertise of other departments. Clark Landis, chair of the Department of Chemistry and leader in the field of hydroformylation, saw the potential in applying the technique to pyrolysis oils.

Elsewhere, Professor Manos Mavrikakis in the chemical and biological engineering department applied state-of-the-art modeling techniques, which delivered new insight at the molecular level. Professor Victor Zavala also helped to analyze the viable economics of the technique when examining the life cycle of plastic waste.

The team projects that this method would have a significant impact on the recycling industry as it is both more sustainable and offers attractive economic benefits to recycling companies.

Currently, these companies don’t have a really good approach to upgrade the pyrolysis oil… In this case, we can get high-value alcohols worth $1,200 to $6,000 per ton from waste plastics, which are only worth about $100 per ton. In addition, this process uses existing technology and techniques. It’s relatively easy to scale up.

Houqian Li, Postdoctoral Researcher

Environmental Benefits and Sustainability for the Future

With the onus on the potential to radically change the recycling industry, the team has also been clear to stress that their method would reduce greenhouse gas emissions, making it a more environmentally compatible recycling technique.

By creating new and useful products from methods that practice what they preach, the UW-Maddison team feels as though they can introduce some real paradigm-shifting change in the recycling industry. This could also usher in a new wave of sustainability measures for the future, offering policymakers more ways to deal with plastic pollution.

There are so many different products and so many routes we can pursue with this platform technology… There’s a huge market for the products we’re making. I think it really could change the plastic recycling industry.

Professor George Huber, Director of the Department of Energy-funded Center for the Chemical Upcycling of Waste Plastics

The team will now focus its efforts on fine-tuning the process and seeing what other potential gains can be made. They will also attempt to unlock other catalyst and plastic waste combinations to create a wider range of reusable materials.⁴

References and Further Reading

1. (2023) Plastic pollution is growing relentlessly as waste management ... - OECD. Available at: https://www.oecd.org/environment/plastic-pollution-is-growing-relentlessly-as-waste-management-and-recycling-fall-short.htm (Accessed: 17 August 2023).

2. Li, H. et al. (2023) ‘Hydroformylation of pyrolysis oils to aldehydes and alcohols from polyolefin waste’, Science, 381(6658), pp. 660–666. Available at: https://www.science.org/doi/full/10.1126/science.adh1853.

3. Visual feature: Beat plastic pollution (2023) UNEP. Available at: https://www.unep.org/interactives/beat-plastic-pollution/?gclid=CjwKCAjwivemBhBhEiwAJxNWN_D (Accessed: 17 August 2023).

4. Daley, J. (2023) New Recycling Process could find markets for ‘junk’ plastic waste, News. Available at: https://news.wisc.edu/new-recycling-process-could-find-markets-for-junk-plastic-waste/. (Accessed: 17 August 2023).

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