Capturing carbon dioxide: How scientists are grabbing greenhouse gas emissions

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By Neil Murthy –

That may look like a solar panel on the rooftop near Tucson, Arizona. But think again. It a carbon dioxide collector and we may be seeing a lot more just like it in the future.

A prototype collector invented by Klaus Lackner, director of the Center for Negative Carbon Emissions at Arizona State University, is perched on the roof of the center our ability to sponge CO2 out of the air. With temperatures rising and carbon emissions from fossil fuels kicking those temperatures upward, Lackner is tackling greenhouse gases in an  ambitious way. His team of scientists have capitalized on the properties of a unique material—known as anionic exchange resins—that captures carbon dioxide from the atmosphere when the material is dry and releases it when the material is wet. The warm temperatures and low humidity of Arizona make it an ideal place to test this technology, since the material can most effectively capture carbon dioxide in the dry desert air. There’s no humidity to dampen the long leaves of the resin.

Lackner, a professor of sustainable engineering, says that the new technology has the potential to reverse the disturbing trend of rising greenhouse gas emissions that we see with each passing year. When the technology is perfected, Lackner hopes that the collected carbon dioxide can be used in other products.

This year in particular, Lackner and his team have celebrated a major milestone. The scientists developed the small fully-automated table top prototype and that is perched on the roof of their lab building. It captures carbon dioxide 24 hours a day, seven days a week. As of right now however, the unit is unable to process the carbon dioxide further and simply releases the gas into the atmosphere. But it is a promising start, according to Lackner, who started his career as a theoretical physicist.

“What we have demonstrated is that we can actually be out in the real world,” said Lackner. His team is now one step closer to the holy grail of carbon sequestration for industrial use of the gas, closing the loop of the carbon cycle.

“There’s absolutely no doubt that within the next one hundred years, we will need to capture carbon,” said Wallace Broecker, the pioneering climatologist at Columbia University. “But developing acceptable technology is going to take 20 to 30 years. We will need a hundred million of Lackner’s units in order to bring carbon dioxide levels down.”

Lackner introduced his latest prototype for a carbon dioxide collector at the Comer Conference on abrupt climate change this fall, a conference Broecker helps organize each year.

Lackner and his team are now working with 3D print technology to create shapes that maximize the surface areas of the collection resins. Although laboratory tests so far have been promising, it remains to be seen whether these new shapes can be placed out in the open to effectively sequester carbon dioxide from the air, Lackner says.

Carbon dioxide levels ranged from 200 parts per million during the ice ages to 300 parts per million during the interglacial warm spells over the last 1 million years, a record documented in ice cores containing ancient pockets of air. But with fossil fuel emissions collecting in the atmosphere, carbon dioxide levels have reached 400 parts per million—the highest it has ever been in that million year record collected in the ice cores. Carbon dioxide is the thermostat of climate change, sending global temperatures higher. The quest to develop technologies aimed at carbon capture and sequestration has never been more urgent, said scientists at the Comer Conference on abrupt climate change held in Wisconsin this fall.

“The International Panel on Climate Change’s latest report pointed out that, if we look forward in time, all of the scenarios which keep us out of harm are actually scenarios where there are negative carbon emissions,” said Lackner. “So if we really want to be serious about negative carbon emissions, we need a better way of pulling carbon dioxide out of the air, and that is what we provide.”

The first 24-hour rooftop carbon dioxide capture unit at the University of Arizona. Photograph courtesy of Klaus Lackner. (Neil Murthy/Medill)
The first 24-hour rooftop carbon dioxide capture unit at the University of Arizona.
Photograph courtesy of Klaus Lackner. (Neil Murthy/Medill)

Lackner and his team have also been evaluating other materials that demonstrate similar properties to the anionic exchange resin. So far, the team has noted that activated carbon impregnated with sodium or potassium carbonate also demonstrate similar—but much weaker—binding affinities to carbon dioxide.

“It’s never good to be held hostage to a single material,” said Lackner. “Because if somebody said you shouldn’t use this, then you are at a disadvantage because we then have no option.”

Lackner emphasizes the point that economic and political investment is needed to continue the research forward.

“Once we decide that this is an emergency, in a few decades we can go from merely nothing to a very large system. But it requires the forces at work to actually want this to happen,” Lackner explained.

Lackner said he and his team look forward to a world years from now that is no longer dependent on fossil fuels. But we need carbon capture in the interim, scientists say. Even though we are still years away from such a world, Lackner is proud to say that “we are making progress.”

Photo at top: Prototype of a series of carbon dioxide capture units. Lackner hopes to place these units outside to
capture CO2 in the atmosphere. (Courtesy of Klaus Lackner.)

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