New plastic upcycling tech can potentially cut 3 million cars’ worth of greenhouse gases

Researchers have developed a breakthrough upcycling process that can help transform polyethylene (PE)—the most widely used plastic in the world— into polypropylene, which is one of the top 5 most common plastic types in the world.
“Today unfortunately a major fraction of PE is not recycled and accumulates in landfills. The fraction that is collected is recycled in the form of energy through combustion. This recycling approach is not really sustainable,” said Damien Guironnet to over an email. Guironnet is a professor of chemical and biomolecular engineering at the University of Illinois Urbana-Champaign and co-lead author of the research article published in the Journal of the American Chemical Society on Friday.
According to the researchers’ preliminary analysis, if just 20 per cent of the world’s PE plastic production could be recovered and converted using this method, it could reduce as much greenhouse gas emissions as taking three million cars off the road.

The researchers developed a proof-of-concept for upcycling PE plastic—a reactor that creates a flow of propylene, which can be turned into PP using current technology. The reactor does this cutting PE molecules many times into small pieces of propylene molecules. The process begins when a catalyst removes hydrogen from the PE chain, creating a location where a reaction can happen.
After this, a second catalyst splits the chain in two before finally, a third catalyst moves the reaction up the PE chain so that the process can be repeated the first catalyst. When the process is complete, 95 per cent of the finished product is propylene. The other 5 per cent is butene, a chemical that has many uses in the plastic production, gasoline and rubber manufacturing industries.
A similar process has been documented in a research article published in the journal Science on Thursday. According to the researchers, the research team that authored the Science article used a process that is more energy intensive.
Guironnet is confident that the technology is scalable and can be adapted to current industry needs but the research faces a few obstacles before it can be applied at a large enough scale. “The biggest challenge is the catalyst stability. To scale up such a process we will need to identify catalysts that are extremely robust. PE waste always comes with impurities. To remain scalable, we would need to find catalysts that remain unaffected these impurities,” explained Guironnet.
If the researchers manage to find a stable enough catalyst, then the PE that is being upcycled does not need to be as pure but if the catalyst is sensitive, that would mean that the PE has to be cleaned, which will make the solution more expensive.