Frequently Asked Questions

These are some of the questions we have been asked about the ECO2 Project. The answers provided are not intended to give a complete overview of carbon dioxide capture and storage (CCS) but we hope they will provide sufficient background to help explain the ECO2 Project. Further explanations and definitions can be obtained through the ECO2 Project Glossary: The Language of CCS - other links to further information are found within the text.

We welcome further questions for which we will compile answers and add them to this list.

Contact: Kelvin Boot

The ECO2 Project

What is the ECO2 project?

ECO2 is a Collaborative Project funded under the European Commission's Framework Seven Programme Topic OCEAN.2010.3 Sub-seabed carbon storage and the marine environment, project number 265847

The ECO2 Project aims to establish a framework of best environmental practices to guide the management of offshore carbon dioxide (CO2) injection and storage in geological formations deep below the seabed. This includes the quantitative and qualitative assessment of potential and actual impacts on marine ecosystems that may occur at CO2 injection facilities below the seabed and across entire storage sites. (More detail at

ECO2 is a multi-institution project drawing expertise from a wide range of disciplines within science, social science, the law and industry, from across the EU. (For further information on partners

 What is Carbon Dioxide Capture and Storage? 

Carbon Dioxide Capture and Storage (CCS), (sometimes called carbon capture and storage or carbon capture and sequestration)  involves the capture of CO2 from large scale industrial and power plant operations, its transport to a suitable site and injection into a deep geological formation (>800m ) where it will be stored for the long-term (1000’s to 100’000s of years).

CCS has been identified as a potentially effective mechanism for preventing large amounts of CO2 entering the atmosphere, where such CO2 is causing dangerous global warming, and into the ocean where it is causing ocean acidification. CCS is therefore one mitigation activity with the potential to reduce the amount of CO2 entering the atmosphere from the major sources such as coal, gas and oil use, and is being actively investigated and trialled to determine its suitability and to perfect the technologies necessary for its affordable implementation.

Why is sub-seabed storage the focus of the ECO2 project, are there not plenty of sites on land that would be cheaper and easier to use?

The ECO2 scientists and social scientists have been asked to look specifically at the sub-seabed realm to determine best practices for all aspects of CO2 storage in such offshore locations. CO2 storage below the land surface would be easier and cheaper, although in some countries the local populations might prefer offshore locations. Nearly all the large natural gas and oil deposits in Europe occur in rocks beneath the seabed and, as they become depleted, they are potentially highly suitable for CO2 storage.

Indeed some of the technology being utilised for CCS has been developed for use in the marine environment and is already in place, though integration of capture, transport and storage technologies at the large-scale required has not yet been widely demonstrated.

(Further information is available at There are still many technical challenges facing the development of integrated CCS projects with CO2 storage offshore.


Why is the EU Commission paying for this research?

Europe is in the vanguard of studies into climate change and ocean acidification. As a block, the EU has the second largest renewable energy generating portfolio in the world (after China).  The EU has been a leader on CCS though in the past few years planned projects have faced serious delays and the impetus is now stronger in North America and China due to opportunities from Enhanced Oil Recovery using CO2.  CCS is still in its youth and there remain many unanswered questions and the need for revisions of regulations as understanding evolves. Whilst reservoirs have held hydrocarbons for millions of years, replacing them with CO2 is not as simple a process as it may seem. Especially in the sub-seabed realm we still need to ensure stored CO2 remains secure for tens of thousands of years, so minimising leakages and any resultant environmental damage.

In order for CCS to be considered as an acceptable and safe technology, the need for sound scientific investigation and monitoring is paramount. Within the EU area a few small CCS projects are already operating, while in Norway two larger projects are underway. If we are to meet our carbon reduction targets in the EU, it is essential that we develop, amongst other mitigation strategies, further CCS projects. Learning about how to evaluate and monitor potential off-shore CO2 storage sites is essential to ensure they are environmentally safe options.

How many CCS sites are there and where are they?

The Global CCS Institute (, as at January 2013, identified 72 potential large-scale integrated CCS projects (defined as “capturing at least 800,000 tonnes of CO2 annually for a coal-based power plant; or at least 400,000 tonnes annually for other emission intensive industrial facilities”). Of these only 4 are operating on a commercial scale.

Statoil’s Sleipner CCS Project was the world’s first industrial scale CCS project, begun in 1996 it injects around one million tonnes of CO2 annually into an offshore ‘aquifer’ 800m below the seabed.

Sleipner, offshore Norway, is also the main area of study for the ECO2 project and the developer, Statoil, is one of the partners of the project. The ECO2 project is, among other things, the first research project in Europe which is investigating the surroundings of an industrial scale CCS operation thanks to the collaboration of the operator.

In Salah, Algeria, is operated by BP, Sonatrach and Statoil and has also removed around one million tonnes per year of CO2 from natural gas.

Snøhvit, Norway, is a Statoil operated CCS project which separates CO2 from natural gas, prior to liquefaction as LNG, and stores it in a deep saline aquifer reservoir.

(Please see Statoil’s website for further information about Sleipner, In Salah and Snøhvit -,Safety,ClimateAndTheEnvironment/Climate/CarbonCaptureAndStorage/Pages/OurCCSProjects.aspx)

The Weyburn-Midale project, Canada accounts for the storage of three million tonnes of CO2 captured annually from the Dakota Gasification Company’s Great Plains Synfuel Plant. The CO2 is transported to the Weyburn oil field in Canada where it is injected for enhanced oil recovery.

All of the existing projects, with the exception of Weyburn, extract CO2 from natural gas processing, an operation that is necessary in any case to sell on the natural gas. Weyburn captures CO2 from coal. However, other large-scale CCS facilities that capture CO2 from coal are now under construction in North America and at least one smaller-scale integrated CCS facility that also captures CO2 from coal is already operating in China.

There are also a number of Enhanced Oil Recovery projects, which inject CO2 to increase oil extraction in near-to-depleted oil reservoirs. These are good demonstrations of the CO2 injection and storage technology, although they may not be using CO2 captured from power generation or other industrial sources.

There is a larger number of smaller-scale research, development and demonstration projects. A map of current projects worldwide and further information about individual projects has been produced by Scottish Carbon Capture and Storage

Investigating CO2 leaks in the marine environment

Which tools are available for studying CO2 storage? Are they reliable?

Many of the tools and techniques available for studying how CO2 as a gas might behave in sub-seabed storage, or how the reservoir itself might perform to contain the CO2, have been borrowed or modified from existing industrial processes used every day by the oil, gas and water industries.

While these technologies may not have been used in CCS they are considered by engineers and developers to be a reasonable starting point from which to develop more specific methods and equipment. Because the oil and gas industry knows far more about the properties of geological formations which store such fossil fuels, than say aquifers, engineers are more confident about CO2 storage in depleted oil and gas reservoirs; more work is required to establish the same level of knowledge on aquifers.  

Monitoring for the structural integrity of storage sites, the opportunities for CO2 to migrate once ‘stored’, and the detection of potential leaks will be a key part of any CCS project assessment across its various stages and throughout its life.

There is a range of monitoring techniques available, which fall within three main groups: geophysical, geochemical and remote sensing. Each group includes a variety of tools.  A suite of techniques can be selected as appropriate for each specific storage site, potentially enabling the monitoring of the CO2 from reservoir level up to the surface.

One innovative technique that, if demonstrated to be effective, might prove useful concerns the detection of  the sound of bubbles as they are released from the sediment; it is relatively cheap and as a passive technique could monitor several square kilometres of seabed, triggering an alarm as a new stream of bubbles occurs or an existing stream speeds up. (


Can all leaks be detected?

Monitoring to detect leaks from CO2 storage facilities is essential if environmental damage is to be avoided and political and public confidence maintained. In the EU, sub-seabed CO2 storage is governed by an EU Directive and by individual member state obligations under the London Convention. Under EU CCS legislation it is an obligation that site operators monitor storage sites:

One clear challenge is to determine the optimal density of monitoring systems; too sparse a grid would imply that leak events could be over-looked whilst a high-resolution grid could have major cost implications. One solution maybe to employ autonomous underwater vehicles (AUVs) or remotely operated underwater vehicles (ROVs) with operational sonar and carbonate system monitors, coupled with fixed monitoring arrays around specific definable leak sites.


How do you decide monitoring strategies for CO2 leaks?

This is a key part of the expected outcomes of the ECO2 project which has as its aim:

“A comprehensive monitoring concept for storage sites will be developed comprising innovative techniques that are apt to detect different modes and levels of leakage including that of pre-cursors. A suite of tools will be developed which will aim to ‘standardise’ how monitoring is carried out, although it must be recognised that each site will have its own detailed challenges and requirements, so site specific monitoring will be essential.


Potential impacts from a CO2 leak into the marine environment

What are the likely impacts of a CO2 leak?

As a CO2 leak is likely to lower the pH of seawater in its immediate vicinity, lessons learned from studies on the impacts of ocean acidification have helped to guide CCS leak impact studies in the marine environment. However a CO2 leak into seabed sediments or the water column has the potential to be more rapid and more concentrated than ocean acidification, but also it might be of shorter duration. Experience indicates that some marine organisms might be adversely impacted (such as some molluscs) whilst others might benefit (green algae, for example). Although impacts on individual species might have economic implications or be a cause for public sympathy, the concern of scientists is more for populations and ecosystems than for individual species which could be seen as ‘winners’ or ‘losers’. Impacts on a wider-than-species scale and under a range of other parameters, such as temperature, are being investigated by ECO2 scientists. There are currently a number of projects including ECO2 project that are looking at the likely impacts of a CO2 leak from CCS in the marine environment (for example the QICS Project - and the RISCS Project -


How can we predict what the impacts might be in any given area? 

Scientific experience can help to provide plausible scenarios of the impacts of a CO2 leak in the marine environment but each site will have its own characteristics that will vary how it is affected. The impacts of CO2 on marine organisms are becoming better understood, but how those impacts change across time and with distance from a CO2 source is less well known. Environmental modelling which takes data from a number of parameters can process multiple factors to produce a better idea of how, for example, temperature, leakage rate, local currents and biota interact under different scenarios, as a CO2 plume moves across the seabed or up into the water column. The ECO2 Project is unique in bringing together a wide range of scientific and industrial expertise and observation to address this question.


How would the impacts from a CO2 leak compare to other threats to the marine environment?

The impacts of a CO2 leak are likely to be of local significance and, depending on the scale and duration of a leak, its location and the character of local environmental conditions, would be highly variable. Research also indicates that recovery times following a potential short term CO2 leak are likely to be such that effects might be transitory. It is true that such a leak could pose serious threats to small areas and might be compared with a local pollution incident.


Is a leak likely to reach the sea surface and ultimately affect humans? 

There are natural analogues of a CO2 leak, where volcanic activity brings CO2 to the sea surface but although still a possibility, geologists working on CO2 storage consider that the risks to humans are very low. (


Will a CO2 leak affect fish in the water column? 

Just how far up the water column CO2 might ascend will depend on local conditions but if a stream crosses the path of fish there may be some impacts. Experiments carried out on captive (aquarium held) fish showed that exposure to high levels of CO2 altered their sensory responses and behaviour including attraction to rather than avoidance of predators. (, how this would translate into a natural environment, where there is potential dissolution, and the opportunity for fish to swim away, is not clear.  But many years of observations at natural leak sites indicate that fish are not affected since they avoid intensive CO2 leaks. For more information about natural CO2 seepage sites please see -



The ECO2 Project