Plastics are everywhere. They’re in our yogurt cups, grocery bags, shampoo bottles, and even the clingy wrap around last night’s leftovers. And almost all of them are made from a family of plastics called polyolefins — polyethylene and polypropylene. These are the kingpins of single-use trash, produced by the hundreds of millions of tons each year. Yet less than 10% of them are ever recycled.
Why? For one, because they’re built like chemical fortresses. Every bond in a polyolefin chain is a carbon–carbon link, one of the sturdiest in chemistry. They don’t break down easily, which is why these plastics linger in landfills and the environment for decades, slowly fracturing into harmful microplastics.
But another major reason why plastics keep piling up in landfills is that recycling them is a nightmare of sorting. Yogurt cups can’t mingle with milk jugs, and even the tiniest shred of the wrong polymer can ruin an entire batch. That tedious step — sorting mountains of plastic trash by hand or machine — has kept global recycling rates abysmally low.
But now, chemists at Northwestern University and Purdue University say they’ve found a way around the problem: a nickel-based catalyst that can chew through mixed plastic waste without needing to separate it first. Astonishingly, it works even on mixed, dirty waste that includes polyvinyl chloride (PVC), a notorious recycling contaminant
The Problem with Plastic Recycling
“Basically, almost everything in your refrigerator is polyolefin based,” said Yosi Kratish, a research assistant professor at Northwestern and one of the study’s co-leads. “Squeeze bottles for condiments and salad dressings, milk jugs, plastic wrap, trash bags, disposable utensils, juice cartons and much more.”
The numbers are staggering. More than 220 million tons of polyolefins are made each year. A 2023 Nature report pegged global recycling rates for these plastics at less than 10% — and sometimes under 1%. Sorting them is so difficult that most mixed batches go straight into the landfill.
That’s why Tobin Marks, the senior author of the study, wanted something different. “One of the biggest hurdles in plastic recycling has always been the necessity of meticulously sorting plastic waste by type,” Marks said. “Our new catalyst could bypass this costly and labor-intensive step for common polyolefin plastics, making recycling more efficient, practical and economically viable than current strategies.”
A Scalpel Made of Nickel
The new system relies on a single-site organonickel catalyst, anchored to a “superacidic” support of sulfated alumina. In lab experiments, the catalyst turned low-value polyolefins into liquid oils and waxes that could be reused as lubricants, fuels, or even candle wax.
Unlike brute-force methods like pyrolysis — where plastics are baked at 400–700°C until they crack into random goo — this nickel tool works at lower temperatures (around 200°C) and uses hydrogen to carefully break carbon–carbon bonds. The researchers describe it as more scalpel than sledgehammer.
Compared to conventional nickel nanoparticles, the single-site catalyst was far more efficient. In one test, it converted nearly all isotactic polypropylene into liquid hydrocarbons in just 20 minutes, producing “a remarkable iPP conversion of 16.0 g of iPP per gram of catalyst per hour,” the authors of the new study wrote in Nature Chemistry.
Even more impressive: the catalyst could distinguish between different plastics in a mixed pile. It selectively chewed through polypropylene while leaving polyethylene largely intact. That chemical sorting trick has never been seen before in recycling.
When “Unrecyclable” Becomes Recyclable
Then came the real surprise. PVC is a recycling nightmare. Heat it up, and it releases hydrochloric acid that corrodes equipment and poisons catalysts. But when the researchers tossed PVC into the mix, something wild happened. The catalyst didn’t just survive — it worked better.
“Adding PVC to a recycling mixture has always been forbidden,” Kratish said. “But apparently, it makes our process even better. That is crazy. It’s definitely not something anybody expected.”
The team’s data suggest that tiny amounts of hydrochloric acid released by PVC may actually regenerate the acidic support, helping the catalyst keep cutting carbon bonds. Instead of being the plastic that breaks recycling, PVC turned into a strange kind of booster.
The researchers aren’t pretending this is a silver bullet. The catalyst is sensitive to air, and its activity drops after use. But it can be regenerated with a simple aluminum-based treatment, restoring much of its original power.
And most importantly, it’s based on nickel — an Earth-abundant metal — not precious ones like platinum or palladium. That makes scaling up more realistic.
The broader context is clear and still bleak. Global plastic production hit over 400 million tons in 2023 and is expected to nearly triple by 2050. Without breakthroughs, we’re looking at a future buried under plastic.
This nickel catalyst isn’t a complete answer. But it hints at a new way to think about plastic not as indestructible waste, but as a stubborn resource that — if coaxed right — can be broken down and reborn.
