Capturing carbon underground has long been considered a potential way of dealing with greenhouse gas emissions and limiting climate change. But is it the best way forward?
Challenges include the amount of carbon dioxide that can be safely stored, and its high cost.
Also, plants with carbon capture and storage (CCS) require more energy to operate, so burn additional fossil fuels and increase the pollution caused by extracting and transporting fuel.
Worryingly, the capacity for safe storage is also far less than was previously thought, according to a paper published by researchers from Imperial College London.
Limiting global warming to 1.5C above pre-industrial levels as prescribed by the 2015 Paris agreement would mean isolating 8.7 gigatonnes of CO₂ per year. But this amount would surpass the safe limit of storage, the paper says. Understandable, as just one gigatonne equates to twice the mass of all the humans in the world and 8.7 the weight of 1.7 billion elephants.
The report, published in the science and technology journal Nature, also identified issues of cost and unintended pollution of groundwater.
One of the authors, Joeri Rogelj, said carbon storage should be seen as a “scarce resource” not “an unlimited solution to bring our climate back to a safe level”.
Sedimentary basins, such as depleted hydrocarbon fields or deep saline aquifers within the basins, have the potential to be used as carbon capture storage areas. So the authors of the report mapped the viable sedimentary deposits for carbon as opposed to the total sedimentary deposits across the globe.
Experts have strong views about the prospects for carbon storage, and Ben Caldecott, director of the Oxford Sustainable Finance Group, said even the downgraded study estimates for storage capacity were still too optimistic because they did not factor in economic constraints.
“Only a fraction of that estimated will be accessible at a price society will be willing to pay,” he said.
The news comes as Conservative Party leader Kemi Badenoch says her party will remove all Net Zero requirements on oil and gas companies drilling in the North Sea if elected. The need to work on technologies such as carbon storage would also be removed, she said.
She announced a plan to focus solely on “maximizing extraction” to “get all our oil and gas out of the North Sea” and avoid higher energy bills for households.
The Labour government, which has committed to banning new exploration licences, said these actions would “only accelerate the worsening climate crisis”.
What is Carbon Capture and Storage (CCS)?
It is a process by which CO2 from industrial installations is separated before it is released into the atmosphere, then transported to a long-term storage location. The CO2 is captured from a large point source, such as a natural gas processing plant and is typically stored in a deep geological formation.
Around 80 per cent captured annually is used for enhanced oil recovery, a process by which CO2 is injected into partially depleted oil reservoirs in order to extract more oil and then is largely left underground.
The past:
Oil and gas companies first used the processes involved in CCS in the mid-20th century. Early technologies were mainly used to purify natural gas and increase oil production. Beginning in the 1980s and accelerating in the 2000s, CCS was discussed as a strategy to reduce greenhouse gas emissions.
Around 70pc of announced CCS projects have not materialized, with a failure rate above 98pc in the electricity sector. As of 2024, CCS was in operation at 44 plants worldwide, collectively capturing about one-thousandth of global carbon dioxide emissions, of which 90pc of operations involve the oil and gas industry.
The future:
CCS could have a critical but limited role in reducing greenhouse gas emissions. However, other emission-reduction options such as solar and wind energy, electrification, and public transit are less expensive and much more effective at reducing air pollution.
Given its cost and limitations, CCS is envisioned to be most useful in specific niches such as heavy industry and plant retrofits. In the context of huge cuts in natural gas consumption, CCS can reduce emissions from natural gas processing. In electricity generation and hydrogen production, it could complement a broader shift to renewable energy.
