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Scientists are advancing a promising solution to two of the world’s biggest challenges - plastic pollution and clean energy - by transforming waste plastics into valuable fuels using sunlight.

A new paper led by Adelaide University PhD candidate Xiao Lu explores how solar-powered technologies can convert discarded plastics into hydrogen, syngas and other useful industrial chemicals, offering a pathway toward a more sustainable, circular economy.

Globally, more than 460 million tons of plastic are produced each year, with millions of tons leaking into the environment. At the same time, the urgent need to reduce reliance on fossil fuels has driven the search for cleaner energy sources.

The research, published today in Chem Catalysis, highlights how plastics - rich in carbon and hydrogen - can be repurposed as an untapped resource rather than waste.

“Plastic is often seen as a major environmental problem, but it also represents a significant opportunity,” said Ms Lu. “If we can efficiently convert waste plastics into clean fuels using sunlight, we can address pollution and energy challenges at the same time.”

The process, known as solar-driven photoreforming, uses light-activated materials called photocatalysts to break down plastics at relatively low temperatures. These reactions can produce hydrogen - a clean fuel with zero emissions at the point of use - as well as other valuable chemicals used in industry.

Unlike traditional water splitting for hydrogen production, plastic-based photoreforming is more energy-efficient because plastics are easier to oxidise, and the process is potentially more viable for large-scale application.

Recent studies have demonstrated impressive results, according to senior author Professor Xiaoguang Duan from the School of Chemical Engineering at Adelaide University.

Researchers have achieved high rates of hydrogen production, acetic acid and even diesel-range hydrocarbons. In some cases, conversion systems have operated continuously for more than 100 hours, highlighting their growing stability and performance.

However, this study also outlines significant challenges that must be overcome before the technology can be widely deployed.

“One major hurdle is the complexity of plastic waste itself,” Prof Duan said. “Different types of plastics behave differently during conversion, and additives such as dyes and stabilizers can interfere with the process. Efficient sorting and pre-treatment are therefore essential to maximize performance and product quality.”

Another challenge lies in the design of photocatalysts. These materials must be both highly selective and durable, able to withstand harsh chemical conditions while maintaining efficiency over time. Current systems can suffer from degradation, limiting their long-term use.

“There is still a gap between laboratory success and real-world application,” Prof Duan said. “We need more robust catalysts and better system designs to ensure the technology is both efficient and economically viable at scale.”

Product separation also remains a key issue. The conversion process often produces a mixture of gases and liquids, requiring energy-intensive purification steps that can reduce overall sustainability benefits.

To address these challenges, the researchers call for a more integrated approach, combining advances in catalyst design, reactor engineering and system optimization. Emerging concepts include continuous-flow reactors, multi-energy systems that combine solar with thermal or electrical inputs, and smarter process monitoring to improve efficiency.

Looking ahead, the team outlines a roadmap for scaling up the technology, with targets including improved energy efficiency and continuous industrial operation over the coming decades.

“This is an exciting and rapidly evolving field,” Ms Lu said. “With continued innovation, we believe solar-powered plastic-to-fuel technologies could play a key role in building a sustainable, low-carbon future.”

Source: Adelaide University