Recycling plastic is notoriously frustrating. Sorting different types of plastics, cleaning off food residue, and dealing with contamination often make the process expensive and inefficient.
But a new breakthrough from Northwestern University chemists may change that.
The team has developed a low-cost nickel-based catalyst that can simplify, and perhaps even eliminate, the tedious step of pre-sorting plastic waste.
The new process focuses on polyolefins, a family of plastics that includes polyethylene and polypropylene.
These are the single-use plastics we encounter every day—milk jugs, condiment bottles, snack wrappers, shampoo bottles, and plastic bags.
Polyolefins make up nearly two-thirds of global plastic consumption and are produced at staggering volumes of over 220 million tons each year.
Despite their prevalence, less than 10% of polyolefins are recycled worldwide, mainly because they are chemically stubborn. Their strong carbon–carbon bonds are difficult to break apart, and current recycling techniques are inefficient, energy-hungry, or limited to low-quality products.
With their new nickel catalyst, the Northwestern team offers an elegant solution. The catalyst uses a process called hydrogenolysis, in which hydrogen gas and a catalyst break down plastics into smaller, useful hydrocarbons.
Unlike traditional approaches that rely on costly noble metals like platinum and palladium and require temperatures of 400–700 degrees Celsius, the nickel catalyst operates at much lower temperatures and with far less energy.
It also uses only a fraction of the material compared to previous nickel-based systems, making it far more practical for large-scale recycling.
What makes the catalyst truly impressive is its precision. Instead of indiscriminately breaking down the entire structure of polyolefins, it selectively targets certain bonds, transforming low-value plastics into higher-value oils and waxes. These can be repurposed into fuels, lubricants, and even candles.
The single-site design of the catalyst allows it to act like a surgical scalpel rather than a blunt tool, making the breakdown process more efficient and controlled.
Perhaps the most surprising result came when the team tested the catalyst with plastics contaminated by polyvinyl chloride (PVC). PVC is widely used in pipes, flooring, and medical devices, but it has long been the nemesis of recycling plants because it releases corrosive gases when heated.
Typically, even small amounts of PVC can ruin an entire batch of recyclables. To the researchers’ astonishment, not only did the nickel catalyst survive PVC contamination—it actually worked better. Even with 25% PVC in the mix, the process accelerated rather than slowed down.
This unexpected discovery suggests the catalyst could handle the mixed, messy plastic waste that usually ends up in landfills. Even better, it can be reused multiple times through a simple and inexpensive treatment, making it a sustainable option.
“This could be a game-changer,” says Tobin Marks, senior author of the study.
“If we can recycle plastics without the costly step of sorting, we’ll have a much more efficient and realistic way to deal with the mountains of plastic waste piling up worldwide.”
