A research paper by Adelaide University Ph.D. candidate Xiao Lu suggests that the use of sunlight to convert plastic waste into clean energy represents a ‘significant opportunity’- but still faces challenges in transitioning from laboratory success to real-world application.
In a paper titled “Opportunities and challenges in sustainable fuel production from plastics,” featured in Chem Catalysis, Ms Lu and senior author Professor Xiaoguang Duan from the School of Chemical Engineering examined how solar-based fuel conversion technologies could help repurpose some of the 450+ million tonnes of plastic waste produced each year, whilst reducing reliance on fossil fuels.
Her research found that plastics that are rich in carbon and hydrogen represent an untapped source of clean energy, converted via the process known as solar-driven photoreforming.
“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.”
A more efficient way to generate hydrogen
Solar-driven photoreforming, uses light-activated materials called photocatalysts to break down plastics at comparatively low temperatures. These reactions can produce chemicals used in various industries, as well as hydrogen, which has zero emissions at the point of use.
In terms of generating hydrogen, plastic-based photoreforming is more energy-efficient than the traditional method of water splitting as plastics are easier to oxidize. Photoreforming is also considered more viable for large-scale application.
Other studies have reported high rates of hydrogen production, acetic acid and even diesel-range hydrocarbons, for sustained periods of over 100 hours.
Technical hurdles include durability and degradation risk of the photocatalysts
The photoreforming process still requires energy-intensive purification for the mixture of gases and liquids produced during conversion, which can reduce overall sustainability benefits.
“One major hurdle is the complexity of plastic waste itself,” Professor 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.”
The photocatalysts used in photoreforming need to withstand harsh chemical conditions whilst maintaining efficiency. Questions have been raised about the impact of degradation on long-term use.
“There is still a gap between laboratory success and real-world application,” Professor Duan said. “We need more robust catalysts and better system designs to ensure the technology is both efficient and economically viable at scale.”
The papers go on to call for a more integrated approach to help scale up the technology, targeting improved energy efficiency and continuous industrial operation in the future. There are already concepts emerging that may support these targets, such as continuous-flow reactors, multi-energy systems that combine solar with thermal or electrical inputs, and smarter process monitoring.
“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.”