Carbon dioxide captured from industrial processes can be transformed into clean, sustainable fuels using just the energy from the Sun, University of Cambridge researchers have said.
The researchers have developed a solar-powered reactor that converts captured CO2 and plastic waste into sustainable fuels and other valuable chemical products. In tests, CO2 was converted into syngas, a key building block for sustainable liquid fuels, while plastic bottles were converted into glycolic acid, which is widely used in the cosmetics industry.
The team took CO2 from real-world sources – such as industrial exhausts or carbon captured from the air itself – and concentrated it to transform it into sustainable fuel.
Although improvements are needed before the technology can be used at an industrial scale, the researchers said the project demonstrates the possibility of producing clean fuels without the need for environmentally destructive oil and gas extraction.
“We’re not just interested in decarbonisation, but de-fossilisation: we need to completely eliminate fossil fuels in order to create a truly circular economy,” said lead researcher Professor Erwin Reisner.
“In the medium term, this technology could help reduce carbon emissions by capturing them from industry and turning them into something useful, but ultimately we need to cut fossil fuels out of the equation entirely and capture CO2 from the air.”
The researchers took their inspiration from carbon capture and storage (CCS), where CO2 is captured and then pumped and stored underground.
“CCS is a technology that’s popular with the fossil fuel industry as a way to reduce carbon emissions while continuing oil and gas exploration,” said Reisner. “But if instead of carbon capture and storage, we had carbon capture and utilisation, we could make something useful from CO2 instead of burying it underground, with unknown long-term consequences, and eliminate the use of fossil fuels.”
The researchers adapted their solar-driven technology so that it works with flue gas or directly from the air, converting CO2 and plastics into fuel and chemicals using only the power of the Sun.
By bubbling air through the system containing an alkaline solution, the CO2 selectively gets trapped while the other gases present in air, such as nitrogen and oxygen, harmlessly bubble out. This bubbling process allows the researchers to concentrate the CO2 from air in solution, making it easier to work with.
The integrated system contains a photocathode and an anode. The system has two compartments. On one side is the captured CO2 solution that gets converted into syngas, a simple fuel. On the other side, plastics are converted into useful chemicals using only sunlight.
“The plastic component is an important trick to this system,” said co-first author Dr Motiar Rahaman. “Capturing and using CO2 from the air makes the chemistry more difficult. But, if we add plastic waste to the system, the plastic donates electrons to the CO2. The plastic breaks down to glycolic acid, which is widely used in the cosmetics industry, and the CO2 is converted into syngas, which is a simple fuel.”
Dr Sayan Kar, co-first author of the research paper, said: “This solar-powered system takes two harmful waste products – plastic and carbon emissions – and converts them into something truly useful”.
The scientists are currently working on a bench-top demonstrator device with improved efficiency and practicality to highlight the benefits of coupling direct-air capture with CO2 utilisation as a path to a zero-carbon future.
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