Thousands of tonnes of crushed basalt rock from Aberdeenshire Council’s quarries are being spread across local farms to improve soil quality and remove carbon dioxide from the atmosphere.

Aberdeenshire Council has three quarries, Balmedie, Pitcaple, and Craiglash, which produce more than 200,000 tonnes of aggregates and coated materials per year for internal and external customers.

During the crushing and screening processes, rock dust is produced which is often seen as a waste material.

However, environmental firm UNDO, spreads the basalt which contains a wide range of nutrients including potassium, calcium and potassium on fields.

It also has an alkalising effect on soil, improving pH over time, and making nutrients, such as phosphate, more available to plants and is suitable for all farming types and is accredited by a number of organic farming organisations.

Key to funding the system is the positive environmental impact of basalt which captures carbon through an enhanced rock weathering system (ERW).

The measurable emission reductions from the system are then sold in the form of carbon credits. The sale of the carbon credits allows Undo to provide and spread basalt on farms free of charge.

The firm said the system could reduce the amount of artificial fertiliser required and cost savings from reducing the need for lime.

With the right conditions, it is estimated that for every four tonnes of basalt dust spread, one tonne of carbon dioxide is removed from the atmosphere. The heat-trapping greenhouse gas then stays locked away for hundreds of thousands of years.

The locally sourced crushed basalt rock is spread using existing farming machinery, enabling local people to do carbon removal in their community. The basalt rock is offered free of charge to farmers in close proximity to quarries, with UNDO paying for and managing the spreading of it across farmland.

Because the crushed basalt rock is spread on farms local to the quarries, transportation is kept to a minimum and, so far, the firm has hauled more than 15,600 tonnes from Aberdeenshire Council’s quarries.

Aberdeenshire Council’s Infrastructure Services Committee Chair, Councillor Alan Turner, said: “The great thing about this process is that it's not just reducing carbon emissions in one area of a supply chain in favour of another. It is actually removing carbon dioxide from the air. On a human timescale, it's essentially permanently stored and in a manner that also helps our local farming community.”

Vice-chair Councillor Isobel Davidson added: “To the quarry, this material is essentially waste. It’s encouraging to see a sustainable business model created from waste that helps the region on its journey towards decarbonisation.”

Founded in 2022 in the central belt, UNDO now employs more than 50 people in the UK and US.

Jennifer Brodie, UNDO’s Agriculture Business Development Manager for Northern Scotland said: “In addition to permanent carbon removal, basalt is a mineral-rich volcanic rock full of nutrients and trace elements. We have an ever-extending range of field trials underway to scientifically quantify the benefits we are bringing to the soil and crops and the potential savings to farmers for expensive fertilisers and lime.”