1

2

4

5

3

Deep, unused saline-saturated rocks

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

Depleted oil and gas fields

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

Deep unmineable coal seams

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 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

Enhanced oil and gas recovery

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

1 2 3 4 5

SOURCE: BELLONA, CO2 CAPTURE PROJECT, SHELL

Confining layersImpermeable rock layers effectively seal the liquid CO2 and prevent the gas rising to the surface

Groundwater aquiferProtected from potential CO2 leaks by extra layer of steel and cement around injection pipe

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

Capped oil well

CO2 injection pipeDouble layer steel pipe cemented into 203mm (8in) bore hole

3km

800m

min

imum

A clean waste gas of nitrogen, oxygen and about 10% of the original CO2 flows out into the atmosphere

Waste CO2 gas chilled to 1.7C to speed up the process Chilled CO2 is mixed with ammo-

nium carbonate to produce a clean waste gas and an ammonium barcarbonate slurry

Slurry heated and pumped through a regenerator, where the CO2 is liberated leaving the ammonium carbonate to be reused

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

Slurry

Ammonium carbonate

Clean gas

Carbon capture and storage (CCS)

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

Pre-combustionIn 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

OxyfuelHere 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

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

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 hydrogen-powered vehicle, the demand for electricity will become much greater

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

Energy needs CO2 production and capture

Capture options

CO2 in the atmosphere

CO2 storage optionsCO2 transportation Possible cost recovery options

550 ppm

500 ppm

450 ppm — risk of dangerous climate change

400 ppm

350 ppm

300 ppm

1960 70 80 90 2000 10 20 30 40 50 60 70

Rise in atmospheric CO2, parts per million

Best case impact of CCS — saves over 50ppm by 2070

CCS combined with large increases in renewables, nuclear and efficiency

Projected continuing rise in CO2

Diffusion

Circulation

Fossil fuelcombustion and industrial processes

Re-vegetation

Vegetation

Ocean surface

Respiration

Photosynthesis

Decomposition

Deforestation and land use change

Atmosphere

Fossil fuels

Sedimentary rocks

Sediments

Deep ocean

Soils

Carbon fluxes

Carbon stored

SedimentationCO2 geologicalStorage

CO2 geologicalStorage

Oceanstorage

Oil

Goes to domestic supply

Electricity generation

Petrochemical plants

Cement/steel/refineries etc

Gas

Natural gaswith CO2 capture

Mineral carbonation

Industrial uses

Coal

Futurehydrogen use

Biomass

CO2CO2 capturesites

Oil or gasrecovery

Methanerecovery

CO2injection site

Saline-saturated rock

CO2compression site

How pre-combustion capture worksHow post-combustion capture works

CO2

Energy

Exhaust gaswith CO2

Cleanedexhaust gas

Cooling

CoolingHeatexchanger

HeatingFossil fueland air

Scrubbercolumn

Absorbent

Water

Regeneration

Storage

Steam reforming

Power plant

Absorbent

Air

Energy

Absorbant

Fossil fuel

Steam

Water

Hydrogen

Nitrogen

Scrubbercolumn

CO2

RegenerationCO2 plusAbsorbent

CO2 plusHydrogen

Storage

Depth of storageStorage 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

CO2 and water

WaterCondensation

Powerplant

Air separationunit

EnergyOxygen

Nitrogen

Air

Fossil fuel

Storage

CO2

How capture using oxyfuel combustion works

The carbon cycle

2. Infrared radiation is given off by earth...

3. Most escapes back into spaceallowing the earth to cool

4. But some infrared radiation is trapped by gases in the air (esp CO2), thus reducing the cooling

The greenhouse effectCo2 in its natural state Co2 in its challenging state Co2 in its safe state?Carbon network

Oil field

Oil field

Coal seam

Coal seam

1. Sunlight passes through the atmosphere and warms the earth

5. Increasing levels of CO2 increasesthe amount of heatretained, causing the amosphere and the earth’s surface to heat up

CCS allows 80% to 90% of CO2 to be captured

SOURCE: CO2CRC SOURCE: CO2CRC SOURCE: CO2CRC

Carbon capture can be achieved in three ways. Here is how one post-combustion technology being developed will work

Post-combustionThe 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

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