Some plastics are notoriously difficult to break down and recycle: think nylon textiles and polyurethane foams. Researchers have now developed solar-powered reactor transforms the waste plastic into clean hydrogen fuel and useful industrial chemicals.
Detailed in the journal Joule, the method relies on acid from spent car batteries, offering a route to tackle two waste streams at once. And it could be a cheaper, more sustainable alternative to current chemical-based recycling methods, the University of Cambridge team said in a press release.
The lead-acid batteries used in conventional cars contain hazardous sulfuric acid. At the end of their lives, consumers in most US states are required to return the batteries to a retailer or take them to a hazardous waste facility. These facilities recycle the toxic lead and the corrosive acid.
Chemist Erwin Reisner and his colleagues collected this discarded acid in a technique called solar-driven acid photoreforming. Acid hydrolysis is a well-established industrial process in which acids such as sulfuric acid are used as a catalyst to break molecular bonds and convert starches into smaller simple sugars.
But researchers have not previously used sun-powered systems that use acids to trigger the destruction of plastics. The problem, partly, is that the acid can corrode other materials. So the research team engineered a special light-activated catalyst that can withstand highly corrosive acidic conditions. This photocatalyst is also free of precious metals—which means it’s cheap and plenty.
The team’s two-step reactor first uses the car battery acid to break the long polymer chains in nylon and polyurethane into smaller chemical building blocks such as ethylene glycol. Then, the photocatalyst then converts into hydrogen and acetic acid—the main ingredient in vinegar—when exposed to sunlight.
While this approach won’t replace conventional recycling, the researchers said it could handle contaminated or mixed plastics that are not viable to reuse or recycle right now.
“We’re not promising to fix the global plastics problem,” said Reisner. “But this shows how waste can become a resource. The fact we can create value from plastic waste using sunlight and discarded battery acid makes this a really promising process.”
Source: Papa K. Kwarteng et al. Solar reforming of plastics using acid-catalyzed depolymerization. Joule, 2026.
image: ©Anthropocene Magazine (based on CC Wikimedia image)
