Study shows economic feasibility for capturing carbon dioxide directly from the air

July 24, 2012
Stephanie Didas, a Georgia Tech Ph.D. candidate, loads an aminosilica sample into a custom-built volumetric adsorption system for measuring adsorption isotherms of different carbon dioxide capture materials. Credit: Georgia Tech Photo: Gary Meek

With a series of papers published in chemistry and chemical engineering journals, researchers from the Georgia Institute of Technology have advanced the case for extracting carbon dioxide directly from the air using newly-developed adsorbent materials.

The technique might initially be used to supply carbon dioxide for such as from or . But the method could later be used to supplement the capture of CO2 from power plant flue gases as part of efforts to reduce concentrations of the atmospheric warming chemical.

In a detailed economic feasibility study, the researchers projected that a CO2 removal unit the size of an ocean could extract approximately a thousand tons of the gas per year with operating costs of approximately $100 per ton. The researchers also reported on advances in adsorbent materials for selectively capturing carbon dioxide.

"Even if we removed CO2 from all the flue gas, we'd still only get a portion of the carbon dioxide emitted each year," noted David Sholl, a professor in Georgia Tech's School of Chemical & Biomolecular Engineering. "If we want to make deep cuts in emissions, we'll have to do more – and air capture is one option for doing that."

The Georgia Tech research into air capture techniques was funded by the U.S. Department of Energy. Papers describing the economic analysis and new adsorbent materials were published in the journals ChemSusChem, Industrial and Engineering Chemistry Research, the Journal of Physical Chemistry Letters and the Journal of the American Chemical Society.

Carbon dioxide from large sources such as coal-burning or chemical facilities account for less than half the worldwide emissions of the gas, noted Christopher Jones, also a professor in the Georgia Tech School of Chemical & Biomolecular Engineering. Much of the remaining emissions come from mobile sources such as buses, cars, planes and ships, where capture would be much more costly per ton.

Jones is collaborating with a startup company – Global Thermostat – to establish a pilot plant to demonstrate the direct air capture technique. The technology for capturing carbon dioxide from the air would be similar to that required for removing the gas from smokestack emissions, though CO2 concentrations in flue gases are dramatically higher than those in the atmosphere.

Miles Sakwa-Novak and Ambarish Kulkarni, both Georgia Tech Ph.D. candidates, set up a steam stripping system that can measure the carbon dioxide adsorption and desorption properties of powder samples. Steam stripping is used in adsorbent regeneration. Credit: Georgia Tech Photo: Gary Meek

Flue gases contain about 15 percent carbon dioxide, while CO2 is found in the atmosphere at less than 400 parts per million. That's a factor of 375, notes Sholl, who said the difference in capture efficiency could be partially made up by eliminating the need to transport CO2 removed from flue gas to sequestration locations.

"Because the atmosphere is generally consistent, you could operate the capture equipment wherever you had a sequestration site," he said. "I don't think air capture will ever produce carbon dioxide as cheaply as capturing it from flue gas. But on the other hand, it doesn't seem to be wildly more expensive, either."

Based on his work with Global Thermostat, Jones believes that the costs of an optimized process will prove to be even lower than the estimates of Sholl's team. "Sholl's paper is important because it shows that direct capture of CO2 from the air can be up to ten times less expensive than had been estimated by others," he said. "Process improvements based on their initial modeling study could bring costs down even further."

In its economic analysis, Sholl's team considered all of the energy that would have to be put into the capture process. The cost estimates did not include the capital cost of establishing the capture facilities because the technology is still too new for reliable projections.

The batch extraction process modeled by the Georgia Tech team involves blowing air through a ceramic honeycomb structure coated with dry amino-modified silica material to capture the CO2, then flowing steam through the structure to release the gas. The technique could produce carbon dioxide that is roughly 90 percent pure.

"The technical challenges are similar to those of flue gas capture: demonstration at scale, demonstration of long-term adsorbent stability and demonstration of process feasibility and stability," Jones said. "Increased funding for air capture work is needed, because most of the funding invested in carbon capture over the past decade has been directed at flue gas capture."

Sholl and Jones have also been contributing to work on flue gas treatment, conducting research into adsorbent materials, including theoretical and experimental research into adsorbent alternatives such as metal-organic framework (MOF) materials.

Among their recent papers on direct capture of CO2 from the air are:

  • A Journal of the American Chemical Society paper that described the role of zirconium in producing more efficient amine-based adsorbents. "Past work has focused on maximizing the amount of CO2 captured per gram of adsorbent by adding ever-increasing amounts of amines," Jones explained. "We are the first to show that an alternate strategy is to change the oxide support that the amines lay on, and for a fixed amount of amine, each amine works more efficiently."
  • A paper published in ChemSusChem describing the role played by primary, secondary and tertiary amines in capturing carbon dioxide from ultra-dilute like air. "We showed conclusively that primary amines are responsible for CO2 capture from the air, that secondary amines work to some degree, and that tertiary amines don't absorb from air in any appreciable amount," Jones said.
  • A paper in Industrial & Engineering Research that describes detailed cost estimates for the air capture process.
Jones believes air capture should be among the options developed to address global warming produced by increasing levels of carbon dioxide in the atmosphere.

"Initial demonstrations of the air capture process will probably be targeted for applications that can use the for commercial purposes," Jones said. "As the technology matures, we envision implementing CO2 capture from the air as a climate stabilization strategy, in parallel with CO2 capture from and enhanced utilization of alternative energies."

Explore further: Steam process could remove CO2 to regenerate amine capture materials

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3 / 5 (2) Jul 24, 2012
Even without involving AGW in the discussion, this technology is part of what may be needed for terraforming operations on exoplanets which are inhospitable due to excessive levels of CO2 in the atmosphere. Imagine huge unmanned atmosphere processing plants powered by thorium reactors, robotically transforming an exoplanet's atmosphere in preparation for a human colony to come in 50 or 100 years.
1.3 / 5 (11) Jul 24, 2012
Why? CO2 is not a pollutant. In fact, if we could but get CO2 to 1000ppm in our atmosphere, we could double plant growth rates increasing the supply of food on this rock we call home.
3.4 / 5 (12) Jul 24, 2012
By definition it is.

"CO2 is not a pollutant." - DirtyNappy

You need to get yourself a dictionary and educate yourself.

If you can't afford one then visit your local library.

"if we could but get CO2 to 1000ppm in our atmosphere, we could double plant growth rates increasing the supply of food" - DirtyNappy

CO2 concentration isn't generally the limiting factor for plant growth. Soil nutrients are.

Poor Nappy. Other than nonsense, he has nothing to say.

3.7 / 5 (9) Jul 24, 2012
Why? CO2 is not a pollutant. In fact, if we could but get CO2 to 1000ppm in our atmosphere, we could double plant growth rates increasing the supply of food on this rock we call home.

Great for plants. Not so great for humans.
1 / 5 (5) Jul 24, 2012
Make that $100 per ton PLUS the amortization of the initial expenditures.
To whom do you expect to sell all this CO2?
Will your buyer(s) be willing to pay you $100 per ton, especially when they could make it themselves with only 550 lb of coal at $50/ton?
We're not talking 'carbon credits' here - we're talking the actual commodity.
Keep in mind that the more dilute the feed stock the more expensive per unit is the extraction. Helium, for example, is cheap and easy to extract from natural gas stocks at 2.8%, but horrendously expensive to extract from air at 0.0005%.
not rated yet Jul 24, 2012
Just link this CO2 extraction process to this:

Problem solved! Methane from thin air.
3.3 / 5 (7) Jul 24, 2012
nappy goes by his name and is ignorant and naive
Why? CO2 is not a pollutant. In fact, if we could but get CO2 to 1000ppm in our atmosphere, we could double plant growth rates increasing the supply of food on this rock we call home.
Its not a fact you dunderhead its a hope and ignorant guess !

Anything in the wrong amount is a pollutant !

Too much CO2 shifts plant chemical equilibrium so they also start to make more poisons such as hydrogen cyanide, this is already happening in tubers such as Cassava in africa and people are getting permanently paralysed or dying as a result.

The same type of issue is more than likely with clover which is a major cattle and sheep crop in europe. Wouldn't be nice if higher CO2 ends up wiping out our meat food and causing other unplanned equilibrium shifts.

There is some suggestion higher CO2 affects corn too but we are not sure yet what exactly it does long term - corn popular in USA.

1000ppm CO2 over such a short period is sheer idiocy !
2.3 / 5 (3) Jul 24, 2012
We humans are supremely arrogant in thinking that this planet we infest was created for our benefit. The planet will survive, we most probably will not. If as it seems we have achieved the pinnacle of our evolution then we are on the way out as a species. Mass panic over a bit of melt water or an increase in CO2 is ridiculous. Just as an aside how do the proponents of AGW explain the huge increases in CO2 that presaged the end of the previous glaciations? There were no people around to cause it.
5 / 5 (1) Jul 25, 2012
This website is literally swarming with trolls.
1 / 5 (1) Jul 28, 2012
"Plant more trees." - Freeman Dyson (is smarter than you are).
not rated yet Jul 29, 2012
I wonder if these new CO2 extraction techniques are being considered for the CO2 scrubbers on the ISS. Even with steam being a requirement. (Solar concentrator could be used.)

@LariAnn checkout it mostly mentions terraforming Mars where there is a bunch of CO2 already. I've read of plans for something like this to collect CO2 and then use other materials to make Methane for rocket fuel to be used on a return trip from Mars. Methane is also a more powerful greenhouse gas that could be produced to make Mars warmer. Getting rid of CO2 won't make oxygen though. Also this doesn't get rid of it, just concentrates it. Seeding an exoplanet with a genetically modified algae or something else that can create oxygen could be a good start. It would likely take many thousands of years to terraform a world. Could take hundreds or thousands of years to get to another star system if FTL isn't invented.

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