Greener carbon capture comes closer

New Canadian research may help scientists design a system that captures carbon without guzzling water and energy like current methods do.

Capturing carbon dioxide before it reaches the atmosphere and storing it underground is one way governments are hoping to reduce greenhouse gas emissions, which have been linked to global warming.

To capture carbon before it escapes from the smokestacks of factories or power plants, the emissions are bubbled through water that contains dissolved chemicals called amines. The amines grab onto the carbon dioxide, and later heat is used to recover the trapped carbon for storage. A huge amount of energy is consumed in heating the water during that process.

By 2030, this kind of carbon capture technology could boost water consumption in the U.S. electricity sector by 80 per cent or 7.5 billion litres per day, the U.S. Department of Energy's National Energy Technology Laboratory reports.

In addition, a typical coal-fired power plant would have to boost its output by more than 20 per cent to cover the extra energy used to capture the carbon.

But findings published Thursday in Science by a team of chemists from the University of Calgary and the University of Ottawa could help engineers design materials that suck up large amounts of carbon — "without generating a lot of CO2 in capturing the carbon," said George Shimizu, one of the article's six co-authors.

He and his colleagues used a technique called X-ray crystallography to watch how carbon dioxide molecules get captured by a porous, solid carbon "trap." A solid material saves energy because no water has to be heated to recover the trapped carbon.

Shimizu likened the trap to a baseball mitt grabbing a carbon dioxide "baseball."

"Obviously, different mitts are going to be better for different sized balls," said Shimizu.

The results showed exactly how the "mitt" and "ball" are shaped, sized and positioned relative to each other.

Meanwhile, collaborators led by Tom Woo at the University of Ottawa created a computer model that calculated how tightly the carbon dioxide was trapped and how easily it could be released again for storage.

"Professor Woo's modelling basically was able to tell us every little finger that was holding the CO2 — how strongly it was contributing," Shimizu said.

The material doesn't grab onto carbon dioxide as tightly as the watery solutions used now, so less energy is needed to release it.

The researchers found that carbon dioxide molecules were sucked into the pores as T-shaped pairs. That means it should be possible to design pores specifically shaped to trap larger clumps of carbon, leading to a high capacity, Shimizu said.

Now that researchers have precisely measured and studied this particular carbon trap, and have a computer model that appears accurate, they should be able to use the computer model to design better carbon-trapping materials.

"It would save us a lot of time in the lab," Shimizu said.