Carbon Capture Versus Direct Air Capture

Carbon Capture Versus Direct Air Capture

Updated November 16, 2021
Carbon Capture Versus Direct Air Capture
Carbon capture and direct air capture (DAC) have gained
same equipment for compression, transfer, and storage. The
prominence in recent years as options to address climate
chemical that does the capturing can also be used
change. The two technologies have similarities (beyond
repeatedly.
their names), but they also have differences. Key
differences include how the technologies work, where the
Both technologies are in early stages of development, with
technology can be used, how the technology can address
a few examples of operating projects worldwide. Of the
climate change, and levels of federal support.
two, CCUS is more mature, though researchers expect
significant technology advancement can still be achieved.
Congress affirmed its support for these technologies in
Section 40301 of the Infrastructure Investment and Jobs Act
Although the capture technologies are different for CCUS
(IIJA; P.L. 117-58): “carbon capture and storage
and DAC, they face similar challenges. Both are typically
technologies are necessary for reducing hard-to-abate
capital-intensive and energy-intensive. Also, the demand
emissions from the industrial sector, which emits nearly 25
for CO2 is small compared to its availability, resulting in
percent of carbon dioxide emissions in the United States ...
low CO2 revenues. The low value of CO2 presents a hurdle
carbon removal and storage technologies, including direct
to commercialization for both technologies.
air capture, must be deployed at large-scale in the coming
decades to remove carbon dioxide directly from the
Where Can They Be Used?
atmosphere ... large-scale deployment of carbon capture,
CCUS can be us ed at stationary sources of CO2 such as
removal, utilization, transport, and storage—is critical for
power plants or other industrial facilities. Existing facilities
achieving mid-century climate goals; and will drive
can be retrofitted to add CCUS equipment, or CCUS can be
regional economic development, technological innovation,
integrated into the design of new facilities. The type of
and high-wage employment.”
source can affect the cost of a project because different
sources emit CO2 in different concentrations (purities). All
The following analysis explains key differences between
else being equal, carbon capture can be completed at lower
the two technologies to inform ongoing congressional
cost per ton of CO2 captured for sources with higher-purity
deliberations regarding the merits of these technologies,
CO2 emissions (e.g., ethanol production plants). Sources of
rationale for federal support, and funding level
captured CO2 are often located far away from where CO2
considerations. Additional information, such as costs and
may be used or stored, creating logistical and cost
other challenges, is provided in other CRS resources, listed
challenges related to the transport of CO2.
below.
DAC can be used anywhere. Many proposals envision
How Do They Work?
building DAC projects close to either inexpensive
Carbon capture technologies prevent the release of carbon
electricity sources or locations where CO2 can be used or
dioxide (CO2) to the atmosphere. In the most commonly
stored, reducing overall costs.
used arrangement today, a chemical that can “grab” CO2 is
placed in or near the stream of CO
How Can CCUS and DAC Address
2 at a s ource. The
captured CO
Climate Change?
2 is then releas ed and compressed s o that it can
be transferred by pipeline. The CO2 can then be used, for
CCUS would reduce CO2 emissions released to the
example, as a feedstock to an industrial process or
atmosphere. The extent of reduction is dependent upon the
permanently stored (sequestered) underground. The
end use of the CO2. Currently, the main use of captured
chemical that does the capturing can be used repeatedly in
CO2 is for enhanced oil recovery (EOR). In EOR,
the process. The full process is called carbon capture,
compressed CO2 is injected into aging oil wells. This
utilization, and storage (CCUS), or sometimes carbon
process increases oil production while also permanently
capture and storage (CCS).
sequestering some CO2.
Direct air capture technologies remove CO2 from the
Many stakeholders see CCUS as a way to enable continued
atmosphere, even if that CO2 was released many years ago.
use of fossil fuels even if CO2 emissions were restricted in
In many technological approaches, air is forced over a
the United States and abroad. Fossil fuels have operational
chemical that can “grab” CO2. DAC and CCUS may use the
advantages over alternative fuels in many economic sectors.
same chemicals, but some chemicals are better suited for
For example, cement, steel, and petrochemical
each application. Regardless, the supporting equipment
manufacturing all require very high temperatures, currently
must be optimized for the different CO2 concentrations
provided almost exclusively by fossil fuel combustion.
involved in DAC and CCUS. After capture, the process for
CCUS may allow continued use of fossil fuels in these and
DAC is very similar to that used for CCUS and can use the
other sectors with lower CO2 emissions than today.
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Carbon Capture Versus Direct Air Capture
DAC would remove CO2 from the atmosphere. It is one
Congress appropriated $2.7 billion to CCUS-specific
example of carbon removal, sometimes called negative
FECM budget accounts between FY2009 and FY2021
emissions technologies. Proponents see DAC and other
through regular appropriations. Additionally, Congress
carbon removal options as a way to reduce emissions from
provided large (relative to regular appropriations)
so-called hard-to-abate sectors (i.e., those for which non-
appropriations to CCS demonstration projects in the
emitting energy sources are not readily available and for
American Recovery and Reinvestment Act of 2009
which CCUS is not well suited). Additionally, DAC and
(ARRA; P.L. 111-5) and IIJA. ARRA provided $3.4
other carbon removal options can potentially return
billion, mostly for demonstration projects, requiring
atmospheric CO2 concentrations to desired levels in case
projects to spend the money by FY2015. Approximately $1
emissions reductions do not or cannot achieve those levels.
billion went unspent. IIJA provides almost $8.5 billion for
Some studies estimate DAC and other carbon removal
CCUS activities for FY2022-FY2026, including $2.1
options (e.g., afforestation) would need to be deployed at
billion for the establishment of a new Carbon Dioxide
large scales globally to achieve climate targets investigated
Transportation Infrastructure Finance and Innovation
in those studies.
(CIFIA) program.
What Federal Support Exists?
DAC has not been a focus area for DOE research
Congress has provided two main types of support for CCUS
historically, although Congress has recommended various
and DAC to date—research funding and tax credits.
DAC RD&D activities in recent appropriations.
Additionally, Congress directed the Department of Defense
Beginning in the late 2000s, the Department of Energy’s
to use $8 million of its FY2020 appropriation and $9
(DOE’s) coal research shifted to CCUS, particularly capture
million of its FY2021 appropriation for DAC research. The
technologies and geological sequestration. These research,
Energy Act of 2020 authorized several DOE carbon
development, and deployment (RD&D) programs are
removal activities, including DAC RD&D activities and a
authorized primarily by the Energy Policy Act of 2005
DAC technology prize competition. IIJA fully funded the
(P.L. 109-58), the Energy Independence and Security Act
technology prize at $115 million and provided an additional
of 2007 (P.L. 110-140), and the Energy Act of 2020
$3.5 billion to develop four Direct Air Capture Hubs,
(Division Z of P.L. 116-260). DOE’s Office of Fossil
defined in the act as a “network of direct air capture
Energy and Carbon Management (FECM) administers these
projects, potential carbon dioxide utilization off-takers,
R&D programs, with a focus on improving CCUS
connective carbon dioxide transport infrastructure,
efficiencies and reducing costs. In the 2005 law, Congress
subsurface resources, and sequestration infrastructure
directed DOE to focus on technologies to capture CO2 from
located within a region.”
coal combustion, especially at power plants. In the 2007
law, Congress expanded the program direction to include
CCUS and DAC projects are both eligible for federal tax
sequestration research, testing, and demonstration. In the
credits proportional to the amount of CO2 they use or store.
2020 law, Congress further expanded the program to
Congress established these tax credits in 2008 (P.L. 110-
natural gas-fired power plants and other industrial facilities ,
343), expanded them in 2018 (P.L. 115-123), and extended
and authorized a carbon utilization RD&D program.
them in 2020 (P.L. 116-260). Under current law, eligible
projects may receive tax credits up to $50 per metric ton of
Figure 1. CCUS Appropriations Since 2009
CO2. Projects must meet certain requirements such as
minimum capture amounts, monitoring procedures, and
start-of-construction deadlines. Changes to these
requirements have been proposed as part of the FY2022
budget reconciliation process.
Additional Resources
Tax credits for which CCUS and DAC may be eligible are
discussed in CRS In Focus IF11455, The Tax Credit for
Carbon Sequestration (Section 45Q).
CCUS technology, existing U.S. projects, and historic
Source: U.S. Department of Energy annual budget justifications for
appropriations for CCUS RD&D are discussed in CRS
FY2009-FY2021; explanatory statement for Consolidated
Report R44902, Carbon Capture and Sequestration (CCS)
Appropriations Act, 2021 (P.L. 116-260); IIJA (P.L. 117-58).
in the United States.
Notes: ARRA = American Recovery and Reinvestment Act of 2009;
Appropriations = regular appropriations to CCUS-specific budget
Appropriations for CCUS and DAC are discussed further in
accounts, FY2009-FY2021; IIJA = Infrastructure Investment and Jobs
CRS In Focus IF11861, Funding for Carbon Capture and
Act. Some ARRA funding went to transport and storage activities;
Carbon Removal at DOE.
some ARRA appropriations went unspent. FY2021 regular
appropriations includes $23 mil ion for utilization. IIJA funding is
Ashley J. Lawson, Analyst in Energy Policy
FY2022-FY2026, some of which is available until expended.
IF11501

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Carbon Capture Versus Direct Air Capture

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