Used in water filtration, poison control, teeth whitening, air filtration, veterinary care, and more, activated charcoal is becoming more common in household products and the broader economy. Now researchers are exploring how to use activated charcoal to accelerate the use of direct air capture (DAC).
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Scientists at the University of Cambridge have been testing ways to make activated charcoal absorb carbon dioxide. While its porous nature allows the material to filter contaminants in air and water, ordinary activated charcoal cannot capture carbon directly from the air on its own. However, the Cambridge researchers thought the substance had potential.
“Some promising work has been done on using porous materials for carbon capture from the atmosphere,” explained Dr. Alexander Forse from the Yusuf Hamied Department of Chemistry, the scientist who led the research. “We wanted to see if activated charcoal might be an option, since it’s cheap, stable and made at scale.”
The Cambridge researchers took an ordinary activated charcoal filter and ‘charged’ it in a way similar to charging batteries by adding a chemical component called hydroxides. When hydroxide ions were added to the activated charcoal, they settled into the porous grooves of the material and bonded with CO2, effectively pulling the carbon out of the atmosphere around it.
To keep the carbon from releasing back into the air, the captured carbon needs to be purified and stored. Researchers accomplished this by heating the activated charcoal to a temperature between 90 and 100 degrees Celsius (194-212° F). The bonds between the captured CO2 and the hydroxide ions were broken at this temperature, allowing the carbon to be removed and sequestered. The scientists used resistive heating, which essentially heats the charcoal filter from the inside out, and makes the process faster and less energy-intensive. The process could also be powered by emissions-free energy sources.
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Other forms of DAC follow similar processes but need to achieve a much higher temperature, sometimes as high as 900 degrees Celsius, and typically rely on natural gas to fuel the process.
While an exciting innovation, the process has its limitations, namely the charcoal cannot absorb CO2 at scale. The team from Cambridge is now looking to address this challenge and scale the technology for commercialization. The researchers have also filed a patent for the innovation support of Cambridge Enterprise, the University’s commercialization arm. “This approach was a kind of crazy idea we came up with during the COVID-19 lockdowns, so it’s always exciting when these ideas actually work,” Forse commented.
Innovative solutions like this are a key part of reducing the cost of direct air capture implementation in the future. Time will tell if companies use activated charcoal for DAC at a commercial scale.
Kelvey Vander Hart is a native Iowan, a member of the American Conservation Coalition, and a communications specialist at Reason Foundation.
