Carbon capture and storage (CCS)
in association with
Energy needs
CO2 production and capture
Towns and cities require vast amounts of
electricity. Power stations burning fossil fuels
are responsible for nearly half of all CO2
emissions. If transport systems in cities are to
switch from oil to electric and hydrogenpowered vehicle, the demand for electricity
will become much greater
Power stations produce electricity by burning gas or coal,
releasing large amounts of CO2 into the atmosphere.
Coal-fired power stations are the biggest offenders and also
the main source of power for fast-growing China and India.
China is completing or opening two 500MW coalfired power
plants every week. While cars, aircraft and buildings are
also major contributors to global warming, the fact that
power stations produce large volumes of CO2 in a single
location makes them an ideal collection point. CCS can also
be fitted to other industrial processes that produce large
quantities of CO2, such as the cement industry
CO2 storage options
CO2 transportation
1
Transporting CO2 from source to
storage site can be carried out through
pipelines, ships, rail or by road, but
low cost and proximity to water make
pipelines the most likely option
CCS allows 80% to 90% of CO2 to
be captured
CO2 released into the atmosphere is the
main contributor to global warming.
In pre-industrial times atmospheric CO2 was
about 280 parts per million. It is now 387
ppm and rising fast. The world is on course
to hit 450 ppm some time after 2030.
The Intergovernmental Panel on Climate
Change is urging a 50%-80% cut in CO2
emissions by 2050. It says carbon capture
and storage could make a large contribution
Rise in atmospheric CO2, parts per million
A clean waste gas of nitrogen,
oxygen and about 10% of the original
CO2 flows out into the atmosphere
Carbon capture can be achieved
in three ways. Here is how one
post-combustion technology
being developed will work
Chilled CO2 is mixed with ammonium carbonate to produce a clean
waste gas and an ammonium
barcarbonate slurry
Post-combustion
The tried and tested way of removing pollutants, such
as sulfar dioxide, from a power plant is by removing
them from the flue gas after the fossil fuel has been
burnt to generate electricity. In CCS, the CO2 is
separated out, cooled, dried and compressed for
transport. 80-90% of the CO2 from a power plant can
typically be removed in this way, although a plant
fitted with the technology does require between 10%
and 40% more energy than a conventional plant. The
great advantage is that post-combustion technology
can be bolted on to an existing power plant
CCS combined with
large increases in
renewables, nuclear
and efficiency
How post-combustion capture works
Slurry heated and pumped through a
Ammonium carbonate regenerator, where the CO2 is liberated
leaving the ammonium carbonate to be
Slurry
reused
Pre-combustion
In this process, the fossil fuel is gasified, rather than
combusted. This converts the fuel into a mixture of
hydrogen and carbon monoxide, also known as
synthesis gas, or syngas. Reacting the syngas to steam
turns the carbon monoxide into CO2. It can then be
separated from the hydrogen gas, creating streams of
pure CO2 and pure hydrogen. 90% of CO2 can be
removed with this technology, which can only be used
in an integrated coal gasification combined cycle
power station
Oxyfuel
Here the fossil fuel is burned, but in 95% pure oxygen
instead of air, resulting in a flue gas with high CO2
concentrations, which can be condensed and
compressed for transport and storage. Up to 100% of
CO2 can be captured in this way, but to date it has only
been demonstrated on a laboratory and pilot scale.
Much research is needed to develop membranes to
efficiently separate oxygen from air
How pre-combustion capture works
Cooling
Storage
400 ppm
CO2
Storage
Absorbent
Absorbent
CO2
Water
Scrubber
column
350 ppm
Heat
exchanger
Fossil fuel
and air
1960 70
80
90 2000 10
20
30
40
50
60
CO2 can be injected into
unmineable coal mines
because coal absorbs CO2 if it
is sufficiently porous. In the
process the coal releases
previously absorbed methane,
and the methane can then be
recovered. The sale of the
methane can be used to offset
a portion of the cost of the CO2
storage in the early stages of
development
Scrubber
column
Cooling
Fossil
fuel
Steam
Saline-saturated
rock
Energy
CO2
Steam
reforming
CO2 plus
Absorbent
Air
separation
unit
Regeneration
Absorbant
Heating
Oil field
Energy
Oxygen
Power
plant
Nitrogen
2
5
Coal seam
Fossil fuel
SOURCE: BELLONA, CO2 CAPTURE PROJECT, SHELL
Carbon fluxes
Fossil fuel
combustion and
industrial
processes
The greenhouse effect
Co2 in its challenging state
Atmosphere
Carbon stored
Re-vegetation
Respiration
2. Infrared
radiation
is given off
by earth...
Decomposition
Diffusion
Photosynthesis
1. Sunlight
passes through
the atmosphere
and warms
the earth
3. Most escapes
back into space
allowing the
earth to cool
Carbon network
Co2 in its safe state?
Goes to
domestic supply
4. But some infrared
radiation is trapped
by gases in the air
(esp CO2), thus
reducing the cooling
Biomass
Coal
Cement/steel/
refineries etc
Electricity
generation
Gas
Mineral
carbonation
CO2
CO2 capture
sites
Future
hydrogen
use
Industrial uses
Ocean surface
Soils
Petrochemical
plants
Oil
Natural gas
with CO2
capture
Vegetation
Deforestation
and land use
change
Ocean
storage
Sediments
Circulation
Fossil fuels
Sedimentation
Deep ocean
5. Increasing levels
of CO2 increases
the amount of heat
retained, causing
the amosphere and
the earth’s surface
to heat up
CO2 geological
Storage
CO2 geological
Storage
Sedimentary rocks
SOURCE: CO2CRC
Oil or gas
recovery
Oil field
3
Co2 in its natural state
Declining oil fields can have
their economic viability
enhanced by the injection of
CO2 — which increases oil and
gas recovery by between four
and 20 percent. The European
Commission estimates the
enhanced oil recovery storage
capacity in the North Sea will
range between 200 million and
1.8 billion tonnes of CO2 over
the next 25 years, depending
on oil and CO2 credit prices
and on how much oil is
recovered
4
After a storage site is full, the
prevention of leakage over the
long term is critical. The site is
capped with a corrosion-resistant
cement plug, several meters thick.
Long-term monitoring of CO2
leakage will also take place at the
surface
1
CO2 and water
Storage
CO2 plus
Hydrogen
Coal seam
70
The carbon cycle
Enhanced oil and gas
recovery
Capped oil well
Confining layers
Impermeable rock layers
effectively seal the liquid
CO2 and prevent the gas
rising to the surface
Water
Condensation
Air
300 ppm
5
Hydrogen
Power plant
Regeneration
Energy
Exhaust gas
with CO2
A coal bed that is unlikely ever
to be mined because it is too
deep or too thin may
potentially be used to store
CO2. Technical feasibility
depends on how porous the
coal is. If later mined, the
stored CO2 would be released
Enhanced coal-bed
methane recovery
CO2 injection pipe
Double layer steel pipe cemented
into 203mm (8in) bore hole
Depth of storage
Storage must be at a
minimum depth of
800m but could be 3km
or more. Pressure at
800m is enough to keep
CO2 in a heavy liquid
state, reducing the risk
of it migrating through
fissures to the surface
How capture using oxyfuel combustion works
Water
Nitrogen
Air
Cleaned
exhaust
gas
4
Deep unmineable coal
seams
Methane
recovery
Groundwater aquifer
Protected from potential CO2
leaks by extra layer of steel and
cement around injection pipe
3km
450 ppm — risk of dangerous climate change
These fields offer significant
possibility for storage: in
Europe alone there is thought
to be the capacity to store 14.5
billion tonnes of CO2 offshore
and 13.1 billion tonnes onshore
- although environmentalists
worry that the multiple bore
holes and wells drilled to find
and extract oil and gas can
increase the leakage risk
If CO2 is injected into suitable
saline formations at depths
below 800m various physical
and geochemical trapping
mechanisms would prevent it
from migrating to the surface.
Saline aquifers account for half
the known storage capacity about 1,000bn tonnes of CO2 though they could ultimately
have the capacity to hold as
much as 10,000bn tonnes,
scientists say
The 90% of captured CO2 is pressurised
ready for storage. Compression liquefies
the gas — and at depth this is intensified,
making the CO2 stay liquid
800m minimum
500 ppm
3
CO2
injection site
Capture options
Best case impact of
CCS — saves over
50ppm by 2070
Depleted oil and gas
fields
Clean gas
Waste CO2 gas chilled
to 1.7C to speed up
the process
Projected
continuing
rise in CO2
550 ppm
2
Deep, unused salinesaturated rocks
CO2
compression site
CO2 in the atmosphere
Possible cost recovery options
SOURCE: CO2CRC
SOURCE: CO2CRC