Scientists at Harvard have developed a new method of scrubbing carbon from the atmosphere, and turning it into hydrocarbon fuels that could be burned in airplanes or even cars.
The process has been demonstrated at a small scale and combines common technologies from the pulp and petroleum industries to capture carbon and hydrogenate it back into complex hydrocarbons that could be recycled for fuel.
Most importantly, the cost targets are considered affordable, ranging from $1 to $2.50 to remediate carbon dioxide released by burning a gallon of gasoline. That equates to $94 to $232 per ton of CO2.
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The study appeared in a new scientific journal Joule, and covered in the June issue of The Atlantic.
The process works something like a pulp mill in reverse.
Giant collectors resembling industrial cooling towers capture the carbon dioxide from the air in an alkaline liquid. Because CO2 is a mild acid, it is attracted to the alkaline liquid.
David Keith, Harvard professor of applied physics
In a process similar to a pulp mill, the liquid containing the CO2 is brought to a factory where the acid is separated from the base and frozen into solid pellets, then heated and converted into a slurry.
These processes are not really new in industry, and thus have a good chance of being scaled up, says David Keith, a professor of applied physics at Harvard who founded Carbon Engineering to commercialize his technology. The company is also backed by Bill Gates.
"Taking CO2 out of carbonate solution is what almost every paper mill in the world does," Keith told The Atlantic.
Lastly, the carbon dioxide is combined with hydrogen using the same Fischer-Tropsch process that large refineries use to convert gaseous hydrocarbons to liquid fuels such as gasoline, kerosene, or diesel. Producing new fuel at the end provides a way to pay for the effort.
“What we’ve done is build a (direct-air capture) process that is—as much as possible—built on existing processes and technologies that are widespread in the world,” Keith told The Atlantic. “That’s why we think we have a reasonable possibility of scaling up.”
The Canton Paper Mill, by Flickr user alex_ford
Two key questions are cost and supplies of hydrogen. With small modifications of well-known processes scientists both inside and outside of Carbon Engineering are optimistic that the technology could be expanded to larger operations.
The study implies that falling costs of solar power could produce hydrogen affordably from electrolysis without producing an excessive increase in CO2.
Keith says it is still cheaper to cut emissions of carbon dioxide than to remediate them. His process, though, could provide the means to adapt to climate change for activities that are difficult to do without producing CO2 emissions, such as jet travel and producing concrete.
Carbon Engineering is seeking funding to build a commercial-scale demonstration plant for its process following successful tests at its pilot plant in British Columbia, Canada.
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