Sucking it up

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By 2017-10-18

By Michael Gregson

Some scientists and engineers believe that if we can't meet the international targets to cut the amount of carbon dioxide that we release into the atmosphere, we will have to start sucking CO2 out of the air as well.

"We really only have less than 20 years left at current emission rates to have a good chance of limiting emissions to less than 2°C," says Chris Field, Director of the Stanford Woods Institute for the Environment. "So, it's a big challenge to do it simply by decreasing emissions from energy, transportation, and agriculture."

For the last six months, a new carbon capture plant has been sucking CO2 out of the air and selling it to a paying customer. The facility, near Zurich in Switzerland, is the first commercial venture of its kind. The company behind it, Climeworks, believes that by the middle of the century we will need hundreds of thousands of similar plants around the world.

To have a chance of keeping the global temperature from rising more than 2 degrees Celsius, the limit set by the Paris Agreement, moving to a low-carbon economy probably won't be enough.

New Swiss plant

At the new Swiss plant, small fans pull air into collectors, where a sponge-like filter soaks up carbon dioxide. It takes two or three hours to fully saturate a filter, and then the process reverses, the vents close and the collector is heated to 100 degrees Celsius, which releases the CO2 in a pure form that can be sold, made into other products, or buried underground.

"You can do this over and over again," says Jan Wurzbacher, Cofounder and Director of Climeworks. "It's a cyclic process. You saturate with CO2, then you regenerate, saturate, regenerate. You have multiples of these units, and not all of them go in parallel. Some are taking in CO2, some are releasing CO2. That means that overall the plant has continuous CO2 production, which is also important for the customer."

Climeworks' first customer is a neighbouring greenhouse, which uses the CO2 to make its tomatoes and cucumbers grow faster. The company is also in talks with beverage companies that use CO2 in sparkling water.

To have the necessary impact, CO2 capture plants would have to be built on a massive scale.

The first plant in Switzerland can capture 900 tons of carbon dioxide in a year, roughly the same amount put out by 200 cars.

The company calculates that there would have to be 750,000 of the shipping container-sized units to capture just 1% of global emissions.

It seems like a huge number – but the same number of shipping containers pass through the Port of Shanghai every two weeks.

The Stanford Woods scientist, Chris Field, says it's important to remember that the technologies, while promising, are early-stage and as yet unproven. They will certainly face major challenges in scaling up to tackle the problem on a global scale.

Potential of the technology

He also warns that it's critical that people don't get the wrong idea about the potential of the technology. Carbon capture isn't just a licence to pollute even more than we are already doing.

"What we should not be doing is ethically kicking the can down the road and then say, we'll probably figure out something later that we can then utilise," he says.

"Many of the scenarios that come forward in the models that are cost effective do exactly that. They say we'll come up with this technology, based on incomplete information. It will be cheap and effective, the land will be available, and people will embrace this. That might be right, but there's almost no evidence confirming that it's right."

But despite these reservations, Field is very much in favour of carbon capture technology as a partial solution to the problem.

"CO2 removal is a really good idea," he says. "And a lot of the technologies ought to be deployed today. A lot of technologies ought to be explored."

"Air capture costs money, so anything we can do which is cheaper than air capture, we should do it, definitely," says Wurzbacher.

"But we'll need this on top of that. And we'll not only need to develop it today, but we need to start scaling it today."

Capturing carbon, he says, is as important as the planned shift to a low-carbon economy. "It's not either/or," he says. "It's both."



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