RESEARCH HIGHLIGHT - Researchers turn recovered car battery acid and plastic waste into clean hydrogen
Researchers have developed a solar-powered reactor to break down hard-to-recycle forms of plastic waste – such as drinks bottles, nylon textiles and polyurethane foams – using acid recovered from old car batteries, and converting it into clean hydrogen fuel and valuable industrial chemicals.
The reactor, developed by researchers from the University of Cambridge, is powered by the energy from the sun, and could be a cheaper, more sustainable alternative to current chemical-based recycling methods. The team say their method could create a circular system where one waste stream solves another.
Global plastic production exceeds 400 million tonnes per year, yet only 18% is recycled. The rest is burned, landfilled, or leaks into ecosystems. The researchers say that their method, known as solar‑powered acid photoreforming, could help address the global mountain of plastic waste. The researchers engineered a photocatalyst that is robust enough to withstand the highly corrosive effects of acid, while making productive use of the acid inside spent car batteries, which is normally neutralised and discarded.
“The discovery was almost accidental. We used to think acid was completely off limits in these solar-powered systems, because it would simply dissolve everything. But our catalyst developed didn’t – and suddenly a whole new world of reactions opened up.”Professor Erwin Reisner, Yusuf Hamied Department of Chemistry, University of Cambridge
The method developed by Kay Kwarteng, a PhD in the Reisner Lab, and their colleagues first treats waste plastics with the car battery waste acid, breaking the long polymer chains into chemical building blocks such as ethylene glycol, which the photocatalyst then converts into hydrogen and acetic acid (the main ingredient in vinegar) when exposed to sunlight.
“Acids have long been used to break plastics apart, but we never had a cheap and scalable photocatalyst that could withstand them”
“Once we solved that problem, the advantages of this type of system became obvious,” Kay Kwarteng, lead author, Reisner Lab
In laboratory tests, the reactor generated high hydrogen yields and produced acetic acid with high selectivity. It also ran for more than 260 hours without any loss in performance.The method developed by Kwarteng, Reisner and their colleagues first treats waste plastics with the car battery waste acid, breaking the long polymer chains into chemical building blocks such as ethylene glycol, which the photocatalyst then converts into hydrogen and acetic acid (the main ingredient in vinegar) when exposed to sunlight.
In laboratory tests, the reactor generated high hydrogen yields and produced acetic acid with high selectivity. It also ran for more than 260 hours without any loss in performance. In laboratory tests, the reactor generated high hydrogen yields and produced acetic acid with high selectivity. It also ran for more than 260 hours without any loss in performance.
The approach works for multiple types of plastic waste, even those that are currently tough to recycle, such as nylon and polyurethane. This offers a real advancement to current upcycling technologies that do not cover plastics beyond PET.
“It’s an untapped resource. If we can collect the acid before it’s neutralised, we can use it again and again to break down plastics: it’s a real win-win, avoiding the environmental cost of neutralising the acid, while putting it to work generating clean hydrogen,” Kay Kwarteng, Kay Kwarteng, lead author, Reisner Lab
The researchers say their method offers a potential order‑of‑magnitude cost reduction compared with other photoreforming approaches, largely because the acid enables increased hydrogen production rates and can be reused rather than consumed or wasted.
Kwarteng says that although challenges remain – such as ensuring reactors can withstand corrosive conditions – the fundamental chemistry is sound. “These acids are already handled safely in industry,” he said. “The question now is engineering: how do we build reactors that can run continuously and handle real‑world waste?”
The team plans to commercialise this process with the support of Cambridge Enterprise, the University’s innovation arm, and with a UKRI Impact Acceleration Account. The research was supported in part by the Cambridge Trust, the Royal Academy of Engineering, the Leverhulme Trust, the Isaac Newton Trust, and the Engineering and Physical Sciences Research Council (EPSRC), part of UK Research and Innovation (UKRI).
University of Cambridge article.
Reference: Papa K. Kwarteng et al. ‘Solar Reforming of Plastics using Acid-catalyzed Depolymerization.’ Joule (2026). DOI: 10.1016/j.joule.2026.102347
Image credit: Beverly Low