Few words within the final text of the Cop28 deal agreed in Dubai are of greater significance than “unabated”.
Dubbed the UAE consensus, the deal calls for the phasing down of unabated coal power, which is the burning of coal without capturing the greenhouse gas emissions.
This phrasing is seen as controversial by some, who argue that using the word leaves the door open to continued use of fossil fuels.
Here, we consider abatement technology and the controversy surrounding it.
What are abatement technologies and why are they significant?
Coal burning generates slightly more than one-third of the world’s electricity needs, but produces about twice the quantity of CO2 per unit of electricity generated than burning gas.
This means that cutting emissions from coal-fired power generation is seen as particularly important in the bid to achieve net zero.
Abatement technologies, involving carbon capture and storage (CCS), collect some of the carbon dioxide emissions and aim to store them permanently.
CCS, which can involve CO2 being removed or scrubbed from exhaust gases, is also relevant to other carbon-intensive industrial activities, including oil and gas operations and manufacturing steel and cement.
The International Energy Agency (IEA) has described the technology as being able to “contribute … to reducing emissions in key sectors”.
CCS systems are complex, though, and need to be customised to particular applications.
This, according to the International Institute for Sustainable Development, is why they have remained expensive despite having been deployed for more than half a century.
What about storage?
There are a number of locations where captured CO2 can be stored, often underground. These include in saline formations, which are porous rocks that contain salty water, and in unmineable coal seams.
It is crucial that the carbon dioxide is stored permanently and cannot leak, and the US National Energy Technology Laboratory states that several methods offer the prospect of permanent storage.
Deep underground, CO2 can be stored as a “supercritical” fluid, with the density of a liquid but the viscosity – a measure of how easily a substance flows – of a gas.
What are the controversies around CCS and the word unabated?
The European Union and the UK were among the negotiating parties at Cop28 calling for a move away from unabated fossil fuel use. This wording implies that fossil fuels could still be used if emissions were captured by CCS.
Many environmentalists are against this emphasis on CCS, though. They would like fossil fuels to be eliminated completely.
Shady Khalil, campaigns lead at Greenpeace Mena, said this week that the group wanted a commitment to the phasing out of fossil fuels “without all the dangerous distractions such as carbon capturing and nuclear power”.
Dr Alaa Al Khourdajie, a research fellow in the Department of Chemical Engineering at Imperial College London, and a contributing author to a report released by the UN’s Intergovernmental Panel on Climate Change, said there were risks without an agreed standard for abatement.
“The term could be misused, permitting ongoing fossil fuel use under the pretext of abatement, and allowing significant greenhouse gas emissions to persist,” he said.
There are potential loopholes where CCS is used, he said, including the incomplete capture of emissions and the continued “fugitive” emissions – typically leaks – of methane from fossil fuel operations. Methane has a climate change impact many times that of CO2.
Dr Al Khourdajie said abated fossil fuels should require at least 90 to 95 per cent of the carbon dioxide to be captured and fugitive methane emissions to be just 0.5 per cent. Also, the carbon must be stored permanently.
But, he noted, the terminology on “unabated” within the Cop28 text is vague and no such definition is drawn up.
“To safeguard our climate objectives, a substantial reduction in global fossil fuel demand is essential, even if the use of ‘abated’ fossil fuels is considered,” he said.
Could related technology help the world to reach negative emissions?
Similar to CCS is direct air capture (DAC), a fledgling but potentially hugely significant field in which CO2 is sucked out of the atmosphere and turned into a form which can be stored.
The IEA has said DAC could be “crucial” alongside CCS to cancel out greenhouse gas emissions that are hard to prevent.
Some climate analysts say it will be necessary to deploy DAC on a large scale later this century to achieve “negative emissions”, in which more greenhouse gases are removed than are released.
