CARBON SEQUESTRATION
THROUGH DIRECT AIR
CAPTURE
The case for DIRECT AIR CAPTURE
The term direct air capture (DAC) refers to a range of
technologies that use chemicals to capture and concentrate carbon dioxide (CO2 ) from the ambient air. When
this captured CO2 stream is stored geologically or utilized
commercially in non-degradeable products, DAC can
generate net-negative carbon emissions. This fact sheet
explores the opportunities and challenges surrounding
direct air capture.
ABOUT US
The Center for Carbon Removal is a
non-profit initiative of the Berkeley
Energy & Climate Institute. We are
dedicated to curtailing climate
change by igniting action to develop and implement strategies for
removing carbon dioxide from the
atmosphere by:
Conducting research and analysis to highlight
opportunities and address challenges surrounding
carbon removal solutions.
Curating a comprehensive online hub for
high-quality information and discussion about
carbon removal.
Hosting events that engage public, private, and
civil sector organizations to accelerate the development of carbon removal solutions.
DIRECT AIR CAPTURE
THE TECHNOLOGY
Direct air capture (DAC) systems can be thought of as artificial trees. In the way that
trees use photosynthesis to extract CO2 from the air, DAC systems rely on chemicals
capable of selectively binding with CO2 but not other chemicals in the air. Once the
chemicals become saturated with CO2, energy is added to the DAC system (in the
form of heat, humidity, pressure, etc.) to release the CO2 in purified form, and
regenerate the chemicals to repeat the process.
CO2-FREE
AIR
AIR
COLLECTOR
SORBENT
+
CO2
ENERGY
SORBENT
REGENERATION
CO2
STREAM
LEADERS
DAC is not a new technology. Similar systems have been installed in submarines and in space applications for decades (it would be impossible to breathe in these closed environments without DAC).
That said, large-scale DAC systems used to fight climate change are only beginning to emerge
today. There are no commercial-scale deployments of DAC systems for carbon management purposes as of this writing. Today, there are four leading commercial DAC system development efforts,
along with one academic center pursuing DAC research:
Carbon Engineering
BC, Canada
Climeworks
Zurich, Switzerland
Global Thermostat
CA, USA
Carbon Engineering is pursuing a
liquid potassium hydroxide based
system. They have a pilot plant in
Squamish, BC set for an October, 2015
launch date.
Climeworks is employing a novel
sorbent coupled with a temperature
swing to release the captured CO2.
Climeworks has secured a commercial
partnership for CO2 recycling with
Audi.
Global Thermostat is pursuing a DAC
technology based on proprietary
amine sorbents with a temperature
swing for regeneration. Global Thermostat has a pilot plant up and
running at the SRI headquarters in
Menlo Park, CA.
ASU Center For
Negative Emissions
Arizona, USA
Infinitree
NY, USA
Infinitree is using a humidity swing
process for concentrating CO2. They
are targeting the greenhouse market
for initial customers. This technology is
based on the DAC system developed
by now-bankrupt Kilimanjaro Energy.
Center for Negative Emissions at ASU
is an academic group headed by
professor Klaus Lackner and is developing a DAC technology based on a
humidity swing process.
OPPORTUNITIES & ADVANTAGES
Direct air capture technologies can be used for carbon “recycling” or “removal” depending
on the end use for the CO2 stream produced.
USES & STORAGE
RECYCLING
Without strong carbon prices, DAC systems are
likely to be used for recycling CO2 into fuels and
chemicals (as these are the highest value markets
today and provide crucial near-term revenue
streams for DAC technology developers).
REMOVAL
With increased incentives for carbon sequestration
over time, DAC can be deployed as a carbon
removal solution, where the business case for DAC
is based on regulatory incentives for carbon
sequestration.
Enhanced Oil Recovery
Fuels
Chemicals
Greenhouse CO2
Beverage production
Geologic Storage
Carbon negative materials like
plastics and cements.
OTHER ADVANTAGES - DAC systems can be sited anywhere, meaning that they can
eliminate the sometimes costly CO2 transportation step associated with other carbon removal
systems (and with traditional carbon capture and sequestration systems on power plants). In
addition, DAC can be scaled easily and has a relatively small land footprint
CHALLENGES
ENERGY
COSTS
The energy requirements for DAC systems depend on how efficient the air
capture process is, and what ending concentration of CO2 is required. To
get 100% pure CO2 stream at the maximum possible efficiency, an American Physical Society report cites that it takes approximately 497 kJ of
energy to generate 1 kg of compressed CO2. In other words, for every
million tons of compressed CO2 generated from a maximally efficient DAC
system, a 10 MW power plant running at 100% capacity factor is required.
To get to the billion ton scale of CO2 capture viewed by many experts as
climatically significant, DAC systems would then require about 10 GW of
power, equal to about 3 times the capacity of the largest nuclear plant in
the US.
At commercial scale, no one really knows how much direct air capture will
cost. Estimates range from around $60/t CO2 at the low end (for only CO2
capture) to $1000/t at the high end (for both capture and regeneration)
according to a recent National Research Council study. Although it is likely
that the first commercial-scale DAC projects will cost several hundreds of
dollars per ton of concentrated CO2, DAC costs are dependent heavily on
manufacturing costs, which are likely to come down significantly, especially if DAC is manufactured modularly.
DIRECT AIR CAPTURE
DIRECT AIR CAPTURE
How is DAC related to other carbon
capture and storage (CCS)
systems?
In principle, DAC systems are quite
similar to other CCS systems in
terms of the chemicals and
processes used. The main difference is that coal power plants have
around 15% concentration of CO2,
and natural gas around 5%. The
CO2 concentration of ambient air
for DAC, however, is around 0.04%.
This relatively dilute stream of CO2
in the air compared to CO2 coming
out of power plant smokestacks
makes DAC more difficult.
Top: Image of Carbon Engineering DAC pilot project. Bottom: Modular DAC unit from Climeworks.
EXTERNAL RESOURCES
four direct air capture“must reads”
American Physical Society. “Direct Air Capture of CO2 with Chemicals - A Technology Assessment for
the APS Panel on Public Affairs”. June 2011. Robert Socolow et al.
Proceedings of the National Academies of Sciences. "The urgency of the development of CO2 capture
from ambient air." Klaus S. Lackner et al. June 2012.
Carbon Engineering. “Comments on the APS Report on Direct Air Capture”. David Keith and Geoff
Holmes. June 2011.
Proceedings of the National Academies of Sciences. “Economic and Energetic Analysis of Capturing
CO2 from the Ambient Air”. Kurt Zenz House et al. September 2011.
CONTACT US
{
www.centerforcarbonremoval.org
@CarbonRemoval
[email protected]
(510) 664 - 7153
}
CENTER FOR
CARBON
REMOVAL