Carbon dioxide emissions must decrease to nearly zero by 2040 if global warming by the end of this century is to be held to 2 °C. But we may well miss that target. A pilot plant started up last fall at Squamish, British Columbia, is testing a backup plan: sucking carbon dioxide directly out of the air.
Capturing ambient carbon dioxide is a tall order because, for all the trouble it causes, the greenhouse gas makes up just 0.04 percent of the air we breathe. The Squamish plant can capture one ton of carbon dioxide a day. Significantly reducing atmospheric carbon dioxide levels would require thousands of far larger facilities, each sucking millions of tons of carbon per year out of the air.
The plant is the brainchild of Calgary-based Carbon Engineering and its founder, Harvard University physicist David Keith. While some scientists have estimated that direct air capture would cost $400 to $1,000 per ton of carbon dioxide, Keith projects that large plants could do it for about $100 per ton.
“We’ve taken existing pieces of industrial equipment and thought about new chemistries to run through them,” says Adrian Corless, Carbon Engineering’s CEO. The company captures carbon dioxide in a refashioned cooling tower flowing with an alkali solution that reacts with acidic carbon dioxide. That yields dissolved carbon molecules that are then converted to pellets in equipment created to extract minerals in water treatment plants. And the plant can turn those carbonate solids into pure carbon dioxide gas for sale by heating them in a modified cement kiln.
In May the company closed on $8 million of new financing in Canadian dollars ($6.2 million in U.S. dollars) from investors including Bill Gates. Keith also hopes to start winning over skeptics. “Most people in the energy expert space think that air capture is not particularly credible,” he says. “There won’t be incentives and funding in a serious way for these technologies unless people believe that they actually work.”
Next up at Squamish: turning captured carbon dioxide (now vented back to the air) into a low-carbon transportation fuel. By reacting carbon dioxide with hydrogen, Carbon Engineering plans to synthesize a fuel with less than one-third the carbon content of conventional gasoline. Corless estimates the fuels will cost $4 to $6 per gallon, but he expects to fetch a premium in places such as California and the European Union, where mandates require fuel suppliers to reduce their carbon content annually. Ultimately, says Corless, fuel from air capture may prove crucial to break the fossil-fuel dependence everywhere.