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Scientists discover carbon capture has a sparkling future

02 Apr 2009

Carbon dioxide has been stored safely and naturally in underground water in gas fields for millions of years, according to new research that was led by University of Manchester academics.

Sampling at Sheep Mountain, Colorado
Sampling at Sheep Mountain, Colorado

And the discovery by the scientists - from the universities of Manchester, Edinburgh and Toronto - could now have a significant impact on future measures designed to slow climate change.

Cutting levels of carbon dioxide in the atmosphere is crucial in the drive to slow climate change.

And carbon capture and storage has been regarded as one approach to cut the levels of the gas, until cleaner energy sources are developed.

The risks around the long-term storage of millions of cubic metres of carbon dioxide in depleted gas and oil fields have met with some concern, as there was no certainty that the gas would be securely trapped underground.

But now the research - published in Nature today (April 1) - brings carbon capture and storage a step closer.

Project director Professor Chris Ballentine, from the University of Manchester's School of Earth, Atmospheric and Environmental Sciences, says: "We cannot change our society overnight to a low carbon economy. While we are in this transition we have to bury our excess CO2 emissions.

"Developing a clear understanding of how natural systems behave means that when we inject CO2 into similar systems we know exactly where it will go. This verification is essential to provide public confidence in the safety of this disposal technology."

Naturally-occurring carbon dioxide can be trapped in two ways.

The gas can dissolve in underground water - like bottled sparkling water. Alternatively it can react with minerals in rock to form new carbonate minerals, which essentially locks the carbon dioxide underground.

Previous research in this area used computer models to simulate the injection of carbon dioxide into underground reservoirs in gas or oil fields to work out where the gas is likely to be stored.

Some models predict that the carbon dioxide would react with rock minerals to form new carbonate minerals, while others suggest that the gas dissolves into the water. Real studies to support either of these predictions have, until now, been missing.

But in order to find out exactly how the carbon dioxide is stored in natural gas fields, an international team of researchers - led by the University - scrutinised nine gas fields in North America, China and Europe.

They measured the ratios of the stable isotopes of carbon dioxide and noble gases like helium and neon in the gas fields, which were naturally filled with carbon dioxide thousands or millions of years ago.

And they found that underground water is the major carbon dioxide sink and has been for millions of years.

"We've turned the old technique of using computer models on its head and looked at natural carbon dioxide gas fields which have trapped carbon dioxide for a very long time," said Dr Stuart Gilfillan, from the University of Edinburgh.

"By combining two techniques, we've been able to identify exactly where the carbon dioxide is being stored for the first time.

"We already know that oil and gas have been stored safely in oil and gas fields over millions of years.

"Our study clearly shows that the carbon dioxide has been stored naturally and safely in underground water in these fields."

And Professor Ballentine said: "The universities of Manchester and Toronto are international leaders in different aspects of gas tracing.

"By combining our expertise we have been able to invent a new way of looking at carbon dioxide fields.

"This new approach will also be essential for monitoring and tracing where carbon dioxide captured from coal-fired power stations goes when we inject it underground - this is critical for future safety verification."

In the future it is hoped that the new data can be fed into future computer models to make modelling underground carbon capture and storage more accurate.

The work was funded by the Natural Environment Research Council (NERC) and the Natural Sciences and Engineering Research Council of Canada.

Chris Ballentine is pictured with Greg Holland sampling at Sheep Mountain, in Colorado.

Notes for editors

The paper, 'Solubility trapping in formation water as dominant CO2 sink in natural gas fields', appears in Nature 2 April 2009, doi:10.1038/nature07852

For further information contact Professor Chris Ballentine, tel 0161 275 3832, email chris.ballentine@manchester.ac.uk or Deborah Haile in the Media Relations Office at the University of Manchester on 0161 275 8387.