CO2 Capture and Storage
3. How do CO2 capture technologies work?
- 3.1 What capture technologies are currently available?
- 3.2 What are the costs of CO2 capture?
3.1 What capture technologies are currently available?
To capture carbon dioxide
it is first separated from other gases resulting from combustion
or processing. It is then compressed and purified to make it
easier to transport and store.
Carbon dioxide resulting from combustion, particularly in the
electricity sector, can be captured using one of three
||Net amount of CO2 “avoided”
||In commercial use for decades in other,
In a post-combustion system, the
flue gas produced by
combustion of the fuel with air only contains a small fraction
It is captured by injecting the flue gases in a liquid that
selectively absorbs the CO2 (such as a cooled or
compressed organic solvent). Nearly pure CO2 can then
be released from the liquid, typically by heating it or
releasing the pressure. Similar separation processes are already
used on a large scale to remove CO2 from natural
In a pre-combustion system, the primary fuel
is first converted into gas by heating it with steam and air or
oxygen. This conversion produces a gas containing mainly
which can be quite easily separated out. The hydrogen can then
be used for energy or heat production.
Oxyfuel combustion uses pure oxygen to burn
the fuel instead of using air which only contains 20% of oxygen
and a lot of nitrogen. It results in a gas mixture containing
mainly water vapour and
The water vapour is then easily removed from the CO2
by cooling and compressing the gas stream. However, for this
process one must first separate oxygen from the air, which is
fairly complex process.
Similar capture systems are already used in several industrial
processes, such as hydrogen or
urea production, and
3.2 What are the costs of CO2 capture?
Capture systems reduce the
emissions from combustion plants by about 80 to 90%. These
figures take into account the fact that capture systems require
additional energy (see Figure TS.11).
For new fossil fuel power
capture can increase the cost of
electricity production by 35 to 85% depending
on different assumptions in plant design, operation and
financing. This represents 0.01 to 0.03 US$ per
kWh of electricity
||Cost in US$/kWh
|New fossil fuel
plants without capture
||0.03 – 0.06
|New fossil fuel
plants with capture
||0.04 – 0.09
||0.01 – 0.03
Capture costs can also be expressed in US$ per net tonne of
captured. This unit cost varies greatly for different types of
combustion plants and for industrial processes. The unit cost of
capture is generally lower where a relatively pure
CO2 stream is produced, such as in natural gas
processing, hydrogen production, and ammonia production.