New research shows that carbon dioxide (CO₂) emissions can be captured and securely stored beneath deep-seated and impermeable underground rocks.
The findings provide further evidence that a developing technology known as Carbon Capture and Storage (CCS), in which climate changing CO₂ gas emissions from industry are collected and transported for storage underground, is safe.
The researchers studied natural CO₂ gas fields and CO₂ mineral springs in south-east Australia to improve the understanding of how to safely store CO₂ underground.
They measured tiny quantities of noble gases present in the CO₂ of each occurrence, determining their fingerprint. They found that the fingerprints are all very similar in this region, showing that in both the gas fields and mineral springs the CO₂ had come from the same source, the Earth’s mantle. This CO₂ was released from the mantle to the CO₂ gas fields and seeps by volcanic activity in the area.
As there has been no recent volcanic activity in the area, the research shows that the CO₂ within the gas fields has been securely sealed from the atmosphere for thousands of years, beneath an impermeable seal rock.
In the area where the mineral springs are present, there are no seal rocks to trap the natural CO₂, and so it formed natural fizzy water at the surface. However, the CO₂ still retained the same mantle noble gas fingerprint despite travelling a long distance through the rock.
Whilst no engineered CO₂ storage would ever take place in a region that lacked a secure seal rock, the work shows that any unintended leak could be confidently identified by its unique fingerprint.
Dr Rūta Karolytė, who led the research at the University of Edinburgh said:
We were able to show for the first time that noble gases remain very sensitive tracers of the source of CO₂ even after it mixes with large volumes of water. This means that we can use noble gas techniques to sensitively fingerprint stored CO₂ once it is injected underground.
Dr Stuart Gilfillan, who directed the study said:
Our work clearly shows the unique capability of using noble gases to monitor CO₂ injected for geological storage. This paves the way for safe storage of CO₂ in old gas and oil fields, such as those present in the North Sea.
Such an approach can reduce emissions of CO₂ and help to limit the impact of climate change. Adoption of CCS technologies could greatly help the UK cut its greenhouse gas emissions to almost zero by 2050, necessary to meet recently announced targets.
The study, published in Geochimica et Cosmochimica Acta, was supported by the UK Engineering and Physical Sciences Research Council and the Australian research organisation CO₂CRC. The research was completed by an international team from the University of Edinburgh, the Scottish Universities Environmental Research Centre in Scotland and the Universities of Adelaide and Wollongong in Australia.
The paper is available for free for 50 days here: https://authors.elsevier.com/a/1ZG76_OJfxF3R
|Ruta Karolyte collecting gas samples for noble gas analysis at the CO2CRC Otway National Research Facility in Australia. Photo: Stuart Gilfillan|