Rock Dust Spreading

Adding rock dust to farmland could absorb vast amounts of CO2, study finds

Image credit: UKCEH

The addition of crushed rock dust to farmland has the potential to remove and lock up large amounts of carbon dioxide from the atmosphere while boosting crop yields, scientists have said.

A team from the UK Centre for Ecology & Hydrology (UKCEH) applied 56 tonnes of finely ground basalt rock from quarries to three hectares of farmland in Plynlimon, Powys.

The basalt rock dust particles, which are less than 2mm in size, absorb and store carbon at faster rates than occur with the breaking down, or weathering of the naturally occurring rocks at the sites, reducing the timescale from decades to just months.

It’s estimated that the ‘Enhanced Rock Weathering’ process could remove up to two billion tonnes of CO2 a year from the atmosphere globally by 2050. This would include up to 30 million tonnes in the UK – around 30 per cent of annual greenhouse gas removal targets as part of national net zero plans.

While other studies from around the world suggest the process could be very effective in removing greenhouse gases from the atmosphere, there have been no large-scale trials in the UK for country-specific land use and soil systems.

Professor Bridget Emmett, head of soils and land use at UKCEH, says: “Enhanced Rock Weathering offers multiple potential wins. Rock dust could play a key role in meeting net zero and Paris Agreement targets. Meanwhile, the resulting chemical changes in the soil can also aid crop and grass production.

The project includes a whole system assessment of emissions linked to the supply and transport of the rock dust from quarries around the UK, to identifying the potential unintended environmental impacts such as changes in freshwater biodiversity.

Dr Alan Radbourne of UKCEH, who is managing the trials, says: “We hope to understand more of the scale and possible trade-offs this technology might have in the real world.

“However, the magnitude of climate crisis means that it will be just part of the broad mix of nature-based and engineered solutions needed to accelerate greenhouse gas removal. It is also important to remember we need to significantly reduce our emissions in the first place.”

UKCEH has set up greenhouse gas flux chambers on the fields to measure how much carbon dioxide and other greenhouse gases are captured from the atmosphere.

The team will also monitor the amount of carbon stored in soil and transferred to the river, as well as other impacts on biodiversity, grass production and overall water quality. Time-lapse cameras are being used to monitor sheep-grazing patterns in the catchment to see if changes in the forage quality will draw more sheep to the area.

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