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
The technique might initially be used to supply carbon dioxide for such
industrial applications as fuel production from algae or enhanced oil recovery.
But the method could later be used to supplement the capture of carbon dioxide
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
carbon dioxide removal unit the size of an ocean shipping container 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 carbon dioxide 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 and 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 power plants 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 and 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 carbon dioxide
concentrations in flue gases are dramatically higher than those in the
Flue gases contain about 15% carbon dioxide, while carbon dioxide is found
in the atmosphere at less than 400 ppm. 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 carbon dioxide removed from flue gas to
“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
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
carbon dioxide 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 carbon dioxide, then flowing
steam through the structure to release the gas. The technique could produce
carbon dioxide that is roughly 90% 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.
Jones believes air capture should be among the options developed to address
global warming produced by increasing levels of carbon dioxide in the
“Initial demonstrations of the air capture process will probably be targeted
for applications that can use the carbon dioxide for commercial purposes,”
Jones said. “As the technology matures, we envision implementing carbon dioxide
capture from the air as a climate stabilization strategy, in parallel with
carbon dioxide capture from flue gas and enhanced utilization of alternative
Source: Georgia Institute of Technology