A Sparkling future for carbon capture

And this recent finding by a group of international scientists could have a significant impact on future measures designed to reduce climate change.

Lowering levels of carbon dioxide (CO2) in the atmosphere is crucial in the drive to cut down greenhouse gases that are changing average temperatures and causing unseasonal, often dangerous, weather globally.

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

The “safe storage” research was led by academics at the UK’s University of Manchester, along with work from the universities of Edinburgh, Scotland, and Toronto, Canada.

The report

In April 2009 the UK government published its report - Towards Carbon Capture and Storage: Government Response to Consultation. It said the consultation launched in 2008 sought further views on steps that the government could take to prepare for and support the development and deployment of CCS technologies as the only option for delivering significant reductions in combustion (mainly fossil fuel) power station emissions.

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

Professor Chris Ballentine

Project Director

School of Earth, Atmospheric & Environmental Sciences

Manchester University

The consultation was largely based on proposals for a directive for the Geological Storage of Carbon Dioxide published by the EU Commission in January 2008 and was largely intended to inform the UK’s response to the draft directive, as well as its subsequent implementation.

University of Edinburgh

Many widely ranging views were received about what more the government might do to drive the development and deployment of CCS. Given these views, the government expects to undertake a separate consultation later in 2009 on measures to encourage the development and deployment (initially on coal-fired power stations) of CCS.

In the past, the risks around the long-term storage of millions of cubic metres of CO2 in depleted gas and oil fields have met with some concern, because there was no certainty that the gas would be securely trapped underground. But now the research - published in Nature magazine - brings CCS a step closer.

Project Director Professor Chris Ballentine - from Manchester University’s School of Earth, Atmospheric & Environmental Sciences - said: “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,” he added.

We have turned the old technique of using computer models on its head and looked at natural carbon-dioxide gas fields which have trapped CO2 for a very long time

Dr Stuart Gilfillan

Edinburgh University

Naturally occurring CO2 can be trapped in two ways. It can dissolve in underground water, in a method that is similar to bottled sparkling water. Or it can react with minerals in rock to form new carbonate minerals that essentially lock the CO2 underground.

Previous research used computer models to simulate the injection of CO2 into underground reservoirs in gas or oil fields to work out where the gas is likely to be stored. Some models predict that the CO2 would react with rock minerals to form new carbonate matter, while others suggest that the gas dissolves into the water.

Gas tracing

But in order to find out how the CO2 is stored in natural gas fields, an international team of researchers - led by Manchester University - examined nine gas fields in North America, China and Europe.

They measured the ratios of the stable isotopes of CO2 and noble gases, such as helium and neon, in the gas fields that were naturally filled with CO2 a very long time ago. And they found that underground water is the major CO2 sink.

“We have turned the old technique of using computer models on its head and looked at natural carbon-dioxide gas fields which have trapped CO2 for a very long time,” said Dr Stuart Gilfillan, from Edinburgh University, Scotland.

“By combining two techniques, we have been able to identify exactly where the CO2 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 CO2 has been stored naturally and safely in underground water in these fields,” he added.

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 CO2 captured from coal-fired power stations goes when we inject it underground - this is critical for future safety verification.”

In future it is expected that the new data could be fed into computer models to make modelling underground CCS more accurate. The research work was funded by the Natural Environment Research Council and the Natural Sciences & Engineering Research Council of Canada.