Solar-powered reactor from University of Cambridge can convert plastic and greenhouse gases into sustainable fuels

Researchers from the University of Cambridge have developed a system that can transform plastic waste and greenhouse gases into sustainable fuels and other valuable products – using only the energy from the sun.

The researchers have created a solar-powered reactor which converts carbon dioxide (CO2) and plastics into different products that are useful in a range of industries. In tests, CO2 was converted into syngas, a key building block for sustainable liquid fuels, and plastic bottles were converted into glycolic acid, which is widely used in the cosmetics industry. The system can easily be tuned to produce different products by changing the type of catalyst used in the reactor.

Converting plastics and greenhouse gases – two of the biggest threats facing the natural world – into useful and valuable products using solar energy is a significant step in the transition to a more sustainable, circular economy. The results, titled ‘Photoelectrochemical CO2-to-fuel conversion with simultaneous plastic reforming’, are reported in Nature Synthesis journal.

The researchers developed an integrated reactor with two separate compartments: one for plastic, and one for greenhouse gases. The reactor uses a light absorber based on perovskite – a promising alternative to silicon for next-generation solar cells.

The team designed different catalysts, which were integrated into the light absorber. By changing the catalyst, the researchers could then change the end product. Tests of the reactor under normal temperature and pressure conditions showed that the reactor could efficiently convert PET plastic bottles and CO2 into different carbon-based fuels such as CO, syngas or formate, in addition to glycolic acid. The Cambridge-developed reactor produced these products at a rate that is also much higher than conventional photocatalytic CO2 reduction processes.

“Converting waste into something useful using solar energy is a major goal of our research,” said Prof Erwin Reisner from the Yusuf Hamied Department of Chemistry, the paper’s senior author. “Plastic pollution is a huge problem worldwide, and often, many of the plastics we throw into recycling bins are incinerated or end up in landfill.”

“Generally, CO2 conversion requires a lot of energy, but with our system, basically you just shine a light at it, and it starts converting harmful products into something useful and sustainable,” added co-first author Dr Motiar Rahaman. “Prior to this system, we didn’t have anything that could make high-value products selectively and efficiently.”

“Developing a circular economy, where we make useful things from waste instead of throwing it into landfill, is vital if we’re going to meaningfully address the climate crisis and protect the natural world,” said Prof Reisner, also leads the Cambridge Circular Plastics Centre (CirPlas), which aims to eliminate plastic waste by combining blue-sky thinking with practical measures. “And powering these solutions using the Sun means that we’re doing it cleanly and sustainably.”

The research was supported by the EU, the European Research Council, the Cambridge Trust, Hermann and Marianne Straniak Stiftung, and the Engineering and Physical Sciences Research Council (EPSRC), part of UK Research and Innovation (UKRI).

“A solar-driven technology that could help to address plastic pollution and greenhouse gases at the same time could be a game-changer in the development of a circular economy,” said Subhajit Bhattacharjee, the paper’s co-first author. “What’s so special about this system is the versatility and tuneability – we’re making fairly simple carbon-based molecules right now, but in future, we could be able to tune the system to make far more complex products, just by changing the catalyst.”