Geoscience Reference
In-Depth Information
Fuel combustion accounts for 94.4% of all U.S. CO
2
emissions.
2
Electricity generation contributes the largest proportion of CO
2
emissions
compared to other types of fossil fuel use in the United States (
Table 1
).
Electricity-generating plants are among the most likely initial candidates for
capture, separation, and storage or reuse of CO
2
because they are
predominantly large, stationary, single-point sources of emissions. Large
industrial facilities, such as cement-manufacturing, ethanol, or hydrogen
production plants, that produce large quantities of CO
2
as part of the industrial
process are also good candidates for CO
2
capture and storage.
3
This report is a brief summary of what CCS is, how it is supposed to
work, why it has gained the interest and support of some members of
Congress, and what some of the challenges are to its implementation and
deployment across the United States.
This report covers only CCS and not other types of carbon sequestration
activities whereby CO
2
is removed from the atmosphere and stored in
vegetation or soils, such as forests and agricultural lands.
4
CO
2
C
APTURE
The first step in CCS is to capture CO
2
at the source and produce a
concentrated stream for transport and storage. Currently, three main
approaches are available to capture CO
2
from large-scale industrial facilities or
power plants: (1) post-combustion capture, (2) pre-combustion capture, and
(3) oxy-fuel combustion capture. For power plants, current commercial CO
2
capture systems could operate at 85%-95% capture efficiency.
5
The capture
phase of the CCS process, however, may be 80% or more of the total costs for
CCS.
6
Post-Combustion Capture
This process involves extracting CO
2
from the flue gas following
combustion of fossil fuels or biomass. Several commercially available
technologies, some involving absorption using chemical solvents, can in
principle be used to capture large quantities of CO
2
from flue gases. U.S.
commercial electricity-generating plants currently do not capture large
volumes of CO
2
because they are not required to and there are no economic
