Can a plan to 'bury' carbon dioxide underground really work?

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Can 'carbon capture' technology alleviate the climate crisis? (Getty)

It's one of the most ambitious parts of the planned battle against climate change – technologies to 'bury' carbon dioxide (CO2) deep underground.

And scientists have investigated how it works in reality, using depleted hydrocarbon reservoirs where CO2 has been injected as part of the oil recovery process.

Carbon capture and storage (CCS) is one of the new technologies that scientists hope will play an important role in tackling the climate crisis.

It involves the capture of CO2 from the burning of fossil fuels in power generation, which is then stored underground in geological formations.

The UK government recently selected four sites to develop multi-billion-pound CCS projects as part of its scheme to cut from heavy industry 20 to 30 million tonnes of CO2 per year by 2030. Other countries have made similar carbon reduction commitments.

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CO2 has historically been injected into numerous depleted hydrocarbon reservoirs as a means of enhanced oil recovery (CO2-EOR).

Dr Rebecca Tyne, of the Department of Earth Sciences at Oxford University, said: "CCS will be a key tool in our battle to avert climate change. Understanding how CCS works in practice, in addition to computer modelling and lab-based experiments, is essential to provide confidence in safe and secure CO2 geological sequestration." 

In a paper published in the journal Nature, Dr Tyne and Professor Chris Ballentine, also from Oxford University, led a team of international collaborators to investigate the behaviour of CO2 within a CO2-EOR flooded oil field in Louisiana.

Data suggested that up to 74% of CO2 left behind by CO2-EOR was dissolved in the groundwater. 

The study also revealed that microbes converted as much as 13 to 19% of the injected CO2 to methane, which is a stronger greenhouse gas than CO2.

Pipes run through Shell's new Quest Carbon Capture and Storage (CCS) facility in Fort Saskatchewan, Alberta, Canada, October 7, 2021.  REUTERS/Todd Korol
Shell's new Quest carbon capture and storage facility in Fort Saskatchewan, Alberta, Canada. (Reuters)

Professor Ballentine said: "Methane is less soluble, less compressible and less reactive than CO2, so, if produced, it reduces the amount of CO2 we can safely inject into these sites.

"However, now this process has been identified, we can take it into account in future CCS site selection."

Carbon capture and sequestration could work alongside technologies that can capture CO2 directly from the air.

These can work with up to 97% efficiency, another study has found.

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Researchers at the Paul Scherrer Institute PSI and ETH Zurich, both in Switzerland, investigated different technologies to remove CO2 directly from the air.

They cautioned that such technology wouldn’t remove the need to cut carbon emissions, but would instead work alongside carbon reduction to help countries hit their climate goals.

The researchers analysed five different ways to capture CO2 from the air at eight different locations around the world.

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"The technologies for CO2 capture are merely complementary to an overall decarbonisation strategy – that is, for the reduction of CO2 emissions – and cannot replace it," said Christian Bauer, a scientist at PSI's Laboratory for Energy Systems Analysis and a co-author of the study.

"However, they can be helpful in achieving the goals defined in the Paris Agreement on climate change, because certain emissions, for example from agriculture, cannot be avoided." 

Watch: Prince Charles proud of his sons for efforts on climate change

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