What if the solution to two major waste problems – plastic pollution and used car batteries – was the same?
Scientists at the University of Cambridge have developed a solar-powered reactor that does exactly that, transforming hard-to-recycle plastics into clean hydrogen fuel using acid recovered from old car batteries.
The breakthrough offers a fresh take on recycling, targeting materials that typically end up burned, buried, or polluting ecosystems. Globally, more than 400 million tonnes of plastic are produced each year, yet only around 18% is recycled. The rest lingers as an environmental burden.
Now, researchers say their new method – known as solar-powered acid photoreforming – could help change that equation.
At the heart of the system is a specially engineered photocatalyst that can survive in highly corrosive acid. That alone marks a significant shift, as acid has traditionally been avoided in solar-powered chemical systems because it tends to destroy the materials involved.
“The discovery was almost accidental,” said Professor Erwin Reisner, who led the research. “We used to think acid was completely off limits in these systems, because it would simply dissolve everything. But our catalyst didn’t – and suddenly a whole new world of reactions opened up.”
The process begins by treating plastic waste – including drinks bottles, nylon textiles, and polyurethane foams – with acid sourced from discarded car batteries. This breaks the plastics down into smaller chemical building blocks.
When exposed to sunlight, the photocatalyst converts those building blocks into hydrogen fuel and acetic acid, a widely used industrial chemical and the main component of vinegar.
In laboratory tests, the reactor delivered strong hydrogen output and maintained performance for more than 260 hours without degradation. Crucially, it also works on types of plastic that are notoriously difficult to recycle, expanding beyond the limits of many current technologies.
Lead author Kay Kwarteng, a PhD researcher involved in developing the catalyst, said overcoming the acid challenge unlocked the system’s full potential.
“Acids have long been used to break plastics apart, but we never had a cheap and scalable photocatalyst that could withstand them,” he said. “Once we solved that problem, the advantages of this type of system became obvious.”
The use of battery acid adds another layer of efficiency. While the lead from car batteries is routinely recovered, the acid is typically neutralized and discarded as waste. By repurposing it, the team has effectively turned one waste stream into a resource for tackling another.
“It’s an untapped resource,” Kwarteng said. “If we can collect the acid before it’s neutralized, we can use it again and again to break down plastics.”
Researchers believe the approach could significantly reduce costs compared to other recycling technologies, partly because the acid can be reused and helps accelerate hydrogen production.
There are still hurdles to overcome, particularly around building reactors that can handle long-term exposure to corrosive conditions at scale. But the team says the underlying chemistry is already proven.
“This won’t replace conventional recycling,” Reisner said. “But it could complement it by handling mixed or contaminated plastics that currently have no viable route to reuse.”
With plans to move toward commercialization, the technology points to a future where waste isn’t just managed – it’s repurposed into something valuable.
