British solar-powered flow reactor turns captured CO2 into synthetic fuel

A University of Cambridge scientists team, led by professor Erwin Reisner, has created a solar-powered flow reactor that can capture C02 from the air at night and convert it into fuels like diesel, methanol, or ammonia during the day with the help of the sun.

If scaled up, it would theoretically allow people to generate their carbon-neutral fuel anywhere in remote places and make synthetic fuel affordable. Reisner said, “We can build a circular, sustainable economy—if we have the political will to do it.”

Absorbing CO2 at night like trees

The solar flow reactor uses filters at night to absorb CO2 from the air. This is somewhat comparable to what trees do naturally. As trees grow, they take in carbon from the air and store it in wood, plant matter, and soil, making them what scientists call ‘carbon sinks.’ Plants use water, sunlight, and carbon dioxide to create food and oxygen during photosynthesis.

But in the reactor at Cambridge, when the sun heats up the captured gas, it absorbs infrared and ultraviolet radiation, leading to a chemical reaction that creates solar syngas. Syngas, or ‘synthesis gas,’ is a mixture of hydrogen and carbon monoxide, which can be used as an alternative to fossil fuels to generate electricity or produce methanol and synthetic diesel.

One of the team members, Dr. Sayan Kar, believes that if the devices can be made at a larger scale, they could solve the issue of removing carbon dioxide from the atmosphere while creating a clean alternative to fossil fuels.

Net balance is zero

As the CO2 released by burning these fuels was captured initially from the air, it doesn’t add to the total amount of CO2 in the atmosphere, and the balance is nearly zero. “CO2 is seen as a harmful waste product, but it is also an opportunity,” Kar adds.

Professor Erwin Reisner was born and raised in the foothills of the alps in Austria. He studied chemistry at the University of Vienna, the Massachusetts Institute of Technology (MIT), and the University of Oxford. Since 2017, he has been a Professor of Energy and Sustainability at the Yusuf Hamied Department of Chemistry of Cambridge University.

Reisner and his team have worked on solar-powered flow reactors for many years. In January last year, they presented a reactor that converts two distinct waste products, greenhouse gases and plastics, into valuable products.

The first compartment of the reactor converts carbon dioxide to different fuels, depending on the catalyst used. Carbon dioxide can then be converted to syngas to make synthetic fuels. The second component converts plastic into glycolic acid, which is popular in skincare products and cosmetics to help maintain smooth skin and prevent aging.

Changing the catalyst

The team designed different catalysts integrated into the light-absorbing flow reactor. By changing the catalyst, the researchers can change the end product. Tests of the reactor showed that it could efficiently convert PET plastic bottles and CO2 into different carbon-based fuels such as CO, syngas or formate, and glycolic acid.

“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,” said one of the co-authors, Dr. Motiar Rahaman.

The research team has been working on plastic recycling and upcycling for the last five years and published their results in the academic journal Nature Synthesis. Now, they have taken their solar-powered flow reactor to the next level by working with CO2 directly captured from the air.