What is the best way to get rid of greenhouse gases? The Swiss company Climeworks thinks the answer is to feed them to a greenhouse. The company is now building what is expected to be the world’s first plant to do so commercially.
The firm expects to be opening the plant near Zurich in September or October. The plant will suck carbon dioxide out of the ambient air and sell it to an agricultural company to spur the growth of lettuce, cucumbers and tomatoes.
C02 is already taken out of the air in enclosed spaces like submarines and space capsules. Climeworks will be using a similar process called direct air capture (DAC), in which normal ambient air is pushed through a fibrous sponge-like filter material that has been impregnated with chemicals called amines, derived from ammonia, which bind to C02.
Once the filter is saturated, the gas will be released by warming it with the heat generated by a nearby municipal waste incineration plant, then piped to a 4 hectare greenhouse.
The big question for air capture has always been its price. “The American Physical Society estimated that on a large scale C02 could be captured for $600 per tonne,” says Climeworks chief operating officer Dominique Kronenberg. “We expect to equal that and eventually get costs down well below that.”
At that price, taking C02 out of the air is more expensive than removing it from the flue gases of industrial facilities and power plants, where the gas is up to 300 times more concentrated. Capturing flue gas is already happening in a handful of demonstration projects around the globe.
“The advantage of taking it out of the ambient air is that you can do it wherever you are on the planet,” says Kronenberg. “You don’t depend on a C02 source, so you don’t have high costs transporting it where it is needed.”
Fuel from the air
Climeworks will be using funding from the Swiss Federal Office of Energy to fine-tune the plant design to make it run more cheaply and efficiently during the three-year pilot period.
The company hopes that thereafter it will run as a self-sustaining business. The plant will collect between 2 and 3 tonnes of C02 a day. Humans add about 40 billion tonnes of the greenhouse gas to the air annually.
The firm expects to add modules in the future to catch additional C02 that can be used with existing technologies to produce liquid fuels.
Such air capture has its critics. “I think it provides false hope,” says Howard Herzog, senior research engineer at the MIT Energy Initiative. If we are unwilling to use relatively cheap mitigation options, like alternative energies, today, he says, “why should we expect future generations to adopt significantly more expensive measures to deal with C02?”
David Keith of Harvard University, and founder of Carbon Engineering in Calgary, Canada, which is working on its own technology to turn air-captured C02 into fuels, is more upbeat.
“While there is no one silver bullet technology to end climate change, using direct air capture to make fuels is potentially scalable, in a way that biofuels aren’t, because it doesn’t use much land or other resources,” he says.
But for air capture to grow to the point where it makes an impact on our climate crisis, he says, we’ll need to get serious about regulating carbon.
“The answer is really clear,” says Keith. “If there are no restrictions on putting C02 in the air, no incentives, no government price on carbon, then these technologies are dead, but so are other technologies, even wind power and solar would be close to dead.”