Ryan Nelson sprinkles tonnes of 'magic dust' across his farm near Culross, Fife.

The dust is crushed basalt – volcanic rock which can be found in abundance in quarries across the country.

The magic comes from its ability to both capture carbon dioxide from the atmosphere and help crops grow through a process known as enhanced rock weathering.

The dust is being given to farmers for free by a company which hopes to remove millions of tonnes of carbon dioxide from the atmosphere.

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Beechgrove Garden presenter Jim McColl saw the practice being carried out in 2004

Ryan found out about the process after spotting an advert in a farming magazine asking for volunteers to allow the rock to be spread on their land.

It triggered a subliminal memory of basalt being demonstrated on the BBC's Beechgrove Garden.

He recalls seeing presenter Jim McColl applying it to the soil on the TV show about 20 years ago.

Ryan said: "It was on a croft and the crofter smashed up all the rock. The crop of fruit and vegetables that he was getting from this croft was remarkable.”

As well as storing carbon, basalt has been shown in trials to improve both crop yields and the quality of grazing for farmers.

Instead of capturing carbon over millennia, it takes a naturally occurring weathering process and accelerates it.

The rock is crushed up to maximise its exposure to the elements when it's spread across agricultural land.

When it rains, the water droplets absorb small amounts of carbon dioxide from the atmosphere as they fall to the ground.

Once the rain hits the rock a chemical reaction occurs which solidifies the carbon and removes it from the atmosphere.

A company called Undo is now offering basalt free to farmers and sends its own contractors to spread it on the land.

Because it captures carbon, the process is funded by carbon credits which big companies buy to offset their planet warming greenhouse gas emissions.

British Airways, Microsoft and McLaren Racing are among those funding the project.

XinRan Liu, director of science and research with Undo, describes it as a transformative measure in the fight against climate change.

He said: "It's the most scalable technology. We have huge deposits of rock globally ready to go and we have farmlands in every single continent.

"All of that means that we could achieve billions of tons of removal on a very fast timescale for the climate."

He says the silica rock can be found all over the world so it doesn't have to be shipped long distances.

It's also a by-product of the aggregate industry which quarries rocks for use in road building.

The company says it wants to spread enough rock by next year to remove a million tonnes of carbon dioxide from the atmosphere.