Solar powered reactor turns plastic and CO2 into green fuel

Solar-powered reactor to convert plastic and greenhouse gases into clean fuel (Source: Reisner Lab)

Researchers have developed a system that can convert plastic waste and greenhouse gases into sustainable fuels and other valuable products using only solar energy.

Researchers at the University of Cambridge have developed a system that can simultaneously convert two waste streams into two chemical products – the first time this has been achieved in a solar-powered reactor.

The reactor converts carbon dioxide (CO2) and plastics into various products that are used in various industries. The tests converted CO2 into syngas, a key building block of environmentally friendly liquid fuels, and plastic bottles were converted into glycolic acid, which is widely used in the cosmetics industry. The system can be easily customized to produce different products by changing the type of catalyst used in the reactor.

Converting plastic and greenhouse gases – two of the biggest threats facing the natural world – into useful and valuable products using solar energy is an important step towards a more sustainable circular economy. The results are published in the journal Nature Synthesis.

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“Transforming waste into something useful using solar energy is the main goal of our study,” said Professor Erwin Reisner of the Department of Chemistry Yusuf Hamid, senior author of the paper. “Plastic pollution is a huge problem around the world and often a lot of the plastics we throw in our trash cans are incinerated or end up in landfills.”

Reisner also leads the Cambridge Center for Round Plastics (CirPlas), which aims to eliminate plastic waste by combining blue skies with practical measures.

Other solar-powered “recycling” technologies promise to solve the problem of plastic pollution and reduce the amount of greenhouse gases in the atmosphere, but so far they have not been combined into a single process.

Overview of a PEC plant demonstrating CO2 fuel production combined with plastic reforming. (CREDIT: Synthesis of nature)

“Solar-powered technology that can help solve the problem of plastic pollution and greenhouse gases could be a game-changer in the development of a circular economy,” said Subhajit Bhattacharjee, co-author of the paper.

“We also need something customizable so that you can easily make changes depending on the end product you want,” said co-author Dr. Motiar Rahaman.

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

Electrochemical analysis of catalysts. (CREDIT: Synthesis of nature)

The team developed various catalysts that were integrated into the light absorber. By replacing the catalyst, the researchers could change the final product. Testing the reactor at normal temperature and pressure has shown that the reactor can efficiently convert PET plastic bottles and CO2 into various carbon-based fuels such as CO, synthesis gas or formate, in addition to glycolic acid. The reactor, developed at Cambridge, produced these products at a rate that is also much faster than conventional CO2 photocatalytic reduction processes.

“Typically, converting CO2 takes a lot of energy, but with our system, you just light it up and it starts converting harmful products into something useful and sustainable,” Rahaman said. “Before this system, we didn’t have anything that could selectively and efficiently produce valuable products.”

Converting PEC CO2 to fuel combined with PET reforming. (CREDIT: Synthesis of nature)

“What’s special about this system is the versatility and customization – right now we’re making pretty simple carbon-based molecules, but in the future we’ll be able to customize the system to make much more complex products by simply changing the catalyst. Bhattacharji said.

Reisner recently received new funding from the European Research Council to help develop their solar-powered reactor. Over the next five years, they hope to refine the reactor to produce more complex molecules. The researchers say similar methods could one day be used to develop a recycling plant powered entirely by solar energy.

Comparison with representative photocatalytic (PC) and PEC systems. (CREDIT: Synthesis of nature)

“Developing a circular economy where we make useful things from waste instead of throwing them in landfill is vital if we are going to meaningfully address the climate crisis and protect the natural world,” Reisner said. “And powering these decisions with the help of the Sun means we’re doing it cleanly and sustainably.”

The study was supported in part by the European Union, the European Research Council, the Cambridge Foundation, Hermann and Marianne Straniak Stiftung and the Engineering and Physical Sciences Research Council (EPSRC), part of UK Research and Innovation (UKRI). Erwin Reisner is a Fellow of St John’s College, Cambridge.

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Note: Materials provided above by the University of Cambridge. Content can be edited for style and length.

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