Old plastic could end up doing more than clogging land and oceans. Scientists at Adelaide University are working on a way to use sunlight to turn discarded plastic into fuels such as hydrogen.
A study led by Adelaide University PhD candidate Xiao Lu looked at how solar-powered systems can convert waste plastics into hydrogen, syngas and other industrial chemicals. The research was published in Chem Catalysis.
More than 460 million tonnes of plastic are produced worldwide each year, and large amounts end up polluting land and oceans. The study says plastics, which are rich in carbon and hydrogen, can be treated as a resource rather than just waste.
“Plastic is often seen as a major environmental problem, but it also represents a significant opportunity,” Ms Lu said.
“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 is called solar-driven photoreforming. It uses light-sensitive materials known as photocatalysts to break down plastics at relatively low temperatures.
Through that process, plastics can be turned into hydrogen, along with other industrial chemicals. The university said the approach can be more energy-efficient than traditional water splitting for hydrogen production because plastics are easier to oxidize, which lowers the energy needed for the reactions.
Senior author Professor Xiaoguang Duan, from the School of Chemical Engineering at Adelaide University, said recent experiments had produced strong results. Researchers have reported high levels of hydrogen production, as well as acetic acid and diesel-range hydrocarbons.
Some systems have operated continuously for more than 100 hours, showing improved stability and performance.
But Prof Duan said major obstacles remain before the technology can be widely used.
“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 stabilisers can interfere with the process. Efficient sorting and pre-treatment are therefore essential to maximise performance and product quality.”
He said the photocatalysts also need to be highly selective and durable, and able to operate under demanding chemical conditions without losing effectiveness. Current versions can degrade over time, which limits long-term reliability.
“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.”
The reactions can also produce a mix of gases and liquids that must be separated through energy-intensive processes, which can reduce the overall environmental benefits.
The researchers said progress will depend on improvements in catalyst design, reactor engineering and overall system optimisation. Ideas being explored include continuous-flow reactors, systems that combine solar with thermal or electrical energy, and advanced monitoring tools to improve efficiency.
Looking ahead, the team said its goals include lifting energy efficiency and allowing 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.”
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