Rock dust can meet half of the UK’s net zero carbon removal target

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To meet its net-zero target, the UK needs technology to remove CO2 from the atmosphere – and sprinkling rock dust on fields could form a big part of the solution



Environment



25 April 2022

Rock dust and lime spreading on fields

Rock dust and lime being spread on fields before cultivation. The rock dust could remove vast amounts of CO2 from the air

SO-Photography / Alamy

Spreading rock dust across the UK’s farmland could provide almost half of the amount of carbon dioxide removal the country needs to meet its binding net-zero target for 2050, according to a new analysis.

The recent report by the Intergovernmental Panel on Climate Change said the need to remove vast amounts of carbon dioxide from the atmosphere is “unavoidable” if the world’s climate goals are to be met. Enhanced rock weathering, a process in which rocks such as basalt are ground up to increase their surface area and accelerate the natural reactions through which they absorb carbon from the air, has already been found to be a potential large-scale option for those removals.

Now, researchers have taken a more realistic look at the promise this technique could hold in the UK. David Beerling at the University of Sheffield, UK, and his colleagues factored in statistics from past basalt mining and more sophisticated models that account for how soil chemistry affects weathering rates and how the size of the rock particles changes over time.

They found that, by mid-century, sprinkling rock dust on UK fields could allow for the absorption of 6 to 30 million tonnes of CO2 a year. That is up to 45 per cent of the carbon removals needed for the country’s net-zero target. Cumulative removals would be close to the potential from planting new woods.

“It’s got overlooked potential to help with the UK net-zero-by-2050 commitment,” says Beerling. “And it has a number of co-benefits that industrial processes don’t have and it’s highly [cost] competitive.”

One benefit, shown by past studies, is that the ground-up rock can act as a fertiliser, boosting crop yields. Also, while Beerling’s team found that the technique was more expensive than tree planting, it is about half the cost of “direct air capture” (DAC) machines.

The study also found that crushing the rock would need relatively little energy – 0.2 per cent of UK electricity generation in the short term – and that the size of the ground particles makes only a minor difference to how fast they draw down carbon.

Still, the approach remains very much in the research phase, with just three field trials active in the UK. It is also overshadowed by companies driving alternative methods of CO2 removal, such as UK energy firm Drax’s hopes to build a negative-emissions power station that will burn plants and Canadian-based company Carbon Engineering’s plans for a DAC facility in Scotland. The 45 per cent figure would also only be reached in a scenario with more basalt mines than exist today, so there would need to be local buy-in for new ones.

More research should help change attitudes, says Beerling. “I would hope that maybe in five years, we’ll have got policy-makers’ attention,” he says.

Journal reference: Nature Geoscience, DOI: 10.1038/s41561-022-00925-2

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