CO2 leakage - how important is it?

2012-04-02 12:11 by Anja Reitz

If public acceptance of carbon capture and storage (CCS) is potentially the biggest hurdle to the deployment of CCS as a tool in our fight against climate change, then addressing the possibility of CO2 leakage from storage sites is likely to be the greatest single challenge to the future of the use of fossil fuels.

The capture of CO2 is seen by most people as just another industry and the transport of CO2, by ship or by pipeline, raises few eyebrows. Pumping carbon dioxide deep underground for permanent storage is, however, perceived as a technology fraught with risks  in particular because leakage from the site could occur and the CO2 return to the surface and threaten both humankind and the environment.

As a geologist I can be convinced of the safety of storage in a well researched and operated site. I can also accept that the CO2 will stay in the ground for a very long time and, hopefully, forever. There are many naturally occurring CO2 deposits around the world  just as there are natural gas ones  that have been there for thousands and even millions of years. Opponents, of course will point to a number of natural seepages of CO2 that have damaged the local environment in some way and the very small number of larger scale fatal emissions, such as the one resulting from the natural degassing of the waters of Lake Nyos in Cameroon. We can explain that these releases occur or occurred in regions or locations that we would not consider for storage as they are not in geological settings which can safely contain COadequately. But despite having a track record which demonstrates that we can image what is happening hundreds of metres below the surface already it can start to sound a bit too 'black box' for many non-specialists.

The only way we will be able to convince a large number of people is to actually demonstrate it. This not only requires the technology to get the CO2 underground, but to show it is staying there by having monitoring and measuring systems capable of measuring very small leakages.

In much of the world it is not just the general public that is interested in knowing if there is any leakage from a site. Not only do national authorities and industry need to know if there is any leakage, but they need to know the exact extent of the leakage and, in particular, the quantities of CO2 that might have escaped. In the European Union, for example, companies would have to both fix the leak and buy emission allowances for every tonne of CO2 that had escaped. The costs could, in the event of a significant leakage, be very high to the extent that liability for stored CO2 is seen as another potential challenge facing CCS.

It is, therefore, not surprising that a workshop organised by the Nottingham Centre for CCS (NCCCS) and funded by the UK Carbon Capture and Storage Community (UKCCSC) in February this year on the subject ofPotential environmental effects of COleakage in the marine and terrestrial environment: Understanding, monitoring, mitigation was well attended by many experts on storage and that the discussions were very animated. To set the scene, there were  a number of presentations on the present 'state of the art' and description of a number of ongoing research projects, many of which are being funded by the European Commission in the UK, Europe and overseas. Then the participants were divided into four groups  each containing a mixture of researchers/academia, industry and regulators/legislators. Each group was asked to separately respond to eight questions:

  1. What are the requirements and barriers for detecting CO2 leaks in the marine environment?
  2. What are the knowledge gaps concerning potential onshore/offshore leakage scenarios that need further R&D?
  3. Who should be responsible for communicating potential environmental risk of leakage to the general public?
  4. What could be done to mitigate the effects of leakage from an onshore/offshore reservoir?
  5. How can the academic community work effectively with stakeholders to inform concerns of any potential environmental impacts of CCS?
  6. How well equipped are we to quantify leakage onshore/offshore should it occur?
  7. What levels of confidence in the long-term storage of COcan realistically be achieved, and how can they be demonstrated to the satisfaction of regulators and the public?
  8. What further developments are needed in the science and in monitoring techniques to support decision making processes and to inform public opinion?

Discussions on many of these questions could have individually expanded to fill at least a half-day each  and still left people wanting more! In spite of that, following a final plenary session at which each group reported its responses, the organisers have managed to compile a readable report summarising the responses. This report has been published by the NCCCS.

The organisers are at pains to point out that the views and opinions in the report are those given by the delegates to the meeting and do not necessarily reflect the opinion of the whole of the CCS community. However, if you have ever asked yourself any of these very important questions and, I expect, most of us have done  or have your own thoughts on the subjects  I urge you to read the report and give us your views or contact the NCCCS directly.


source: GCCSI blog by Derek Taylor

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