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What is Carbon Capture and Storage (CCS)?

cartoon of underground CO2 storage CCS is essentially a three stage technology where CO2 is captured from large man-made CO2 emission sources, transported via a network of pipelines and stored in deep subsurface geological formations. The capture process can potentially remove 90% of the CO2 generated from fossil fuelled (coal, oil and gas) electricity generation and industrial processes (such as steel and concrete manufacture)- based on the most recent estimates of CO2 emission from fuel combustion (29 Gt in 2009) this would represent a mass of CO2 into the thousands of millions of tons. In order to prevent this large volume of CO2 reaching the atmosphere it can be injected and safely stored in depleted hydrocarbon reservoirs, non-potable saline aquifers or unmineable coal seams (see IPCC report on CCS figure to the left). For a world map of current CCS schemes, see the Scottish Carbon Capture and Storage centre map.

What might Carbon Capture and Storage (CCS) look like?

[CCS cartoon]

The diagram on the left shows a conceptual plan for CCS, involving 2 of the common fossil fuels, methane gas (also called natural gas) and coal.

Methane gas is produced from offshore gas fields, and is brought onshore by pipeline. Using existing oil-refinery technology, the gas is 'reformed' into hydrogen and CO2. The CO2 is then separated by a newly-designed membrane, and sent offshore, using a corrosion-resistant pipeline. The CO2 goes to an oilfield. The CO2 is stored in the oilfield, several km below sea level, instead of being vented into the atmosphere from the power station.

The diagram is available from Scottish Carbon Capture and Storage for download to use for education and outreach activities.


Why is CCS important?

world CO2 emissions, 1990 - 2035 Rising CO2 concentrations in the atmosphere from pre-industrial levels of 280ppm to a present day value of 365ppm has lead to increasing ocean acidification and may be contributing to climate change and a rising of global temperatures. A doubling of man-made CO2 emissions since the 1970's coupled with geological evidence, which shows that changes of this magnitude usually occur over timescales of 5,000 to 10,000 years, suggests that it is likely that man-made CO2 is contributing significantly to this rise in atmospheric CO2. If fossil fuel combustion is allowed to continue to grow unabated then it is projected that CO2 emissions will reach 35.4 Gt a year by 2035. This is inline with the worst case scenario in the IPCC 2007 Climate Change report which couples CO2 rises to a world average temperature increase from 2.4-6.4C by 2100. If the world is to maintain its current dependance on fossil fuels then CCS is a necessary technology for tackling rising atmospheric CO2.


Rising CO2The UK emits more than 500 millions of tonnes of carbon dioxide every year. The quantity has steadily increased since the start of the industrial revolution (1800's). We are not the country that uses the most CO2 per member of the population - but our usage is still high. Worldwide, emissions are still rising. UK CO2 emissions since before the industrial revolution. The image to the right shows data compiled by G. Marland, T. A. Boden and R. J. Andres of ORNL. UK CO2 emissions, pre-industrial revolution to present

How does CO2 affect the climate ?

Global temperatures and atmospheric CO<sub>2</sub> levels, 1880 to 2010 The effects of carbon dioxide in the atmosphere are controversial. However, the average temperature of the Earth is rising, especially when measured at the poles. Note that the average Earth surface temperature correlates well with the amount of CO2 in the atmosphere (i.e. as the CO2 levels in the atmosphere have increased, the surface temperature has gone up at the same time).

For more information, including the science of predicting climate change, click here.

How does CO2 affect the oceans?

About half of the extra CO2 from the atmosphere will dissolve in the oceans, making the water more acidic. The diagram shows how acidic the oceans will become in the future, up to the year 3000. To work this out, it was necessary to:
  1. predict how CO2 emissions will change in the future (the top of the diagram)
  2. calculate how this will change the amount of CO2 in the atmosphere (middle part of the diagram)
  3. finally work out how acidic the oceans will become (bottom part of the diagram)
The acidity is shown as a change in pH units. The effects of this change on marine life is unknown, but could be disastrous.

Diagram from Caldeira, K. & Wickett, M.E. (2003) Nature, v. 425. p. 365
predicted increases in ocean acidity, 1750 to 3000
Surface ocean acidity The effects of making the ocean more acid are absolutely inevitable, and are easy to predict, as it relies on simple chemistry, not on complex computer models of climate. The ocean already holds 400 Billion tons of fossil fuel CO2. Consequently, the ocean is already 0.1 pH units more acid than before industrial CO2 emissions. This means nutrients for plankton in the North Sea, and all shallow ocean waters, are changing rapidly. This is the base of the food chain for invertebrates, shells and, eventually, economic fishing. By 2050 the ocean will be five times more acid than at any time since glaciation (change pH 8.4 to pH 7.8). More information on ocean acidification.

Image adapted from Wolf-Gladrow et al. (1999).

Why is the UK a good place to capture and store CO2?

The UK has numerous oil and gas fields, many of which are becoming emptied of hydrocarbons. These are perhaps the best places to store CO2. A study in 1996 estimated that we have space for about 5.3 Gt CO2 in depleted oilfields (i.e. 5,300,000,000 tonnes), and about 11-15 Gt CO2 in depleted gas fields. This is about about 10 years of total UK CO2 emissions in oilfields, and a further 30 years in gasfields. We have the technical expertise to plan the storage (gained from extracting the oil and gas), and an established industry base that could undertake the work.

There is a second type of geological store, known as saline aquifers. These are porous rocks deep below ground that are full of salty water that is of no use for drinking or agriculture. In the UK, the same 1996 study estimated that we could store 19 - 716 Gt CO2 like this (i.e. up to 716,000,000,000 tonnes) - perhaps sufficient for 500 years of UK emissions. There are more geological problems in using such storage sites, as we know less about the geology. However many of the rocks are similar to oilfields, so there is good reason to suppose that these saline aquifers are well worth investigating in more detail. Infact, the only present day test site for underground CO2 storage in the North Sea uses a saline aquifer at 1km below the seabed, which is sited above the Norwegian Sleipner Field.

When should we do this?

Now! We should start CO2 injection immediately, and expect to have to continue until at least 2050. Hopefully by this time we will have developed lower-carbon technology and have reduced CO2 emissions to levels that are not causing environmental damage.

There is a good reason why we should start CO2 storage sooner rather than later - at the present almost all of the UK offshore oil and gas fields still have their platforms in place - these are the 'oil rigs' that everybody is familiar with from photos in newspapers. These platforms can be modified for CO2 storage, at a fraction of the cost of building and installing new facilites. By the end of the next decade, many of these platforms will have been removed as the oil and gas supplies run dry. New facilities for CCS would hence have to be built, increasing the costs.

What if we do nothing?

The longer we wait, the worse it gets. You may not believe in climate change, but most scientists believe that the evidence of high CO2 levels and hot climates in the past is compelling. You may not care if the summers get a few degrees warmer, but the ocean will inevitably become more acid, and the last time that happened it became a layered green soup (about 50 Million years ago). Click here for more information on predicting climate change in the future.

Like all preventive medicine, it's easier to put off the fateful day. But when that day arrives, it causes you more pain, and costs more, compared to early actions. Its important to realise that, even if we act now, in 2005, the climate will carry on warming for another 3 or 5 degrees Centigrade. That means some parts of the UK may have a climate like southwest France. But where will the Spanish live, and the French, and all the people in North Africa, and all the people in the southern USA, as these areas dry and heat up to become uninhabitable desert?

By acting now, we have a chance to limit that rise to less than 5 Centigrade, by keeping atmospheric CO2 less than 550 parts per million.

What will it cost?

This will cost money, in more expensive fuel costs. However, it will not cost very much. For the world scale, estimates are commonly about 2% of Global Domestic Product. That is one year of normal growth.

Each individual in the UK is responsible for about 10 tons of CO2 each year, and estimates of cost for capture, liquefaction and storage in North Sea aquifers are about 20 pounds per ton. So that costs about 200 pounds per person each year. If energy efficiency is also increased, the cost may be only half of this - 100 pounds per person per year. Thats about 1p or 2p on each electricity unit. Will that be a disaster? Well in the winter of 2004 -05, gas prices incresed far more than that, and in the year 2004, the price of crude oil and petrol increased by far more than that. And nothing catastrophic happened to the UK economy. How much is it worth to keep the world habitable, and the oceans alive?

Don't forget that doing nothing will also cost money, for example in damage caused by rising sea levels and extreme weather events. In a report to the UK Government, Sir Nicolas Stern concluded that it is cheaper to act now, then to wait and pay for the damage.

What next?

The component parts of Carbon Capture and Storage are all present. However the money does not work out yet, because a Generating company needs to pay for capturing the CO2 and transporting CO2 towards a disposal site. Then an Oil company needs to pay to place the CO2 deep below ground.

There are several ways of making CCS economic, all require Government intervention in the market place:
  • Cap and Trade. Companies are given CO2 emissions quotas. If a company exceeds its quota then it has to buy more emissions permits from a company that has not used its allocation up. Hence the permits have a value and can be traded, such as in the European Emissions Trading Sceme (ETS).

  • Tax CO2 emissions. This puts a value on all CO2 emissions to the atmosphere, hence it may become cheaper to capture the CO2 and store it. The Norwegian Government has used this approach.

  • Limit CO2 emissions from power stations in terms of the amount of CO2 per unit of energy generated. For example the UK Conservative Party suggested in summer 2008 that power stations should have a maximum emission limit equivalent to a state-of-the-art gas-fired plant. CCS would hence be required for coal-fired plants (which emit much more CO2 than gas-fired plants), and is paid for by the price difference between gas (expensive) and coal (cheap).

  • Direct Government subsidy. In this method, a private company, or a coalition of power generators, pipeline owners and oil companies, are given the cost difference between the price of building a new conventional fossil-fuel power station, and one with CCS. The difference in operating costs would also be compensated. This is the approach the UK Government is using in the competition to build the first UK CCS scheme, which is ongoing as of spring 2009 with no likelyhood of a decision anytime soon.

  • Legislation directly requiring all new power-stations to have CCS. This is pretty drastic, but could occur if by (say) 2020 the EU's or World's CO2 emissions are still increasing, and there are dramatic signs of irreversible climate damage such as the collapse of the Greenland ice sheet causing global sea-level rise.

In addition, there is EU legislation in preparation that would set legally binding targets for CO2 emissions from member states for the year 2050, and possibly for intermediate years (perhaps 2020?). Some countries are not waiting for this, but are setting their own targets, e.g. the UK. Many experts believe that without CCS, these targets are impossible to reach unless people dramatically and drastically change their lifestyles - no more foreign holidays or air-freighted out-of-season fruit and vegetables?


Following the UK Budget, 22 April 2009, the UK Government announced the following measures to encourage CCS development within the UK:

  • “No new coal without CCS demonstration from day one.”
  • “Full scale retrofit of CCS within five years of the technology being independently judged as technically and commercially proven.”


Last modified: 21 Mar, 2012
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