Rock dust applied to soils may help capture 2B tons of CO2

Rock dust spread over the planet’s farm fields may prove a climate solution with the potential to remove up to two billion tons of carbon dioxide (CO2) from the atmosphere, according to British researchers.

That’s more than the world’s aviation and shipping industries combined, or about half of the current emissions of Europe. The research published last week in the journal Nature looks at how the technique could be used in different countries, with optimism about how some of the world’s highest CO2 emitters, including China, India and Brazil, stand to benefit the most in terms of CO2 removal.

The team of scientists, led by David Beerling of University of Sheffield’s Leverhulme Centre for Climate Change Mitigation, also included experts from institutions in the United States and Belgium, among them global climate leader James Hansen of the Earth Institute at Columbia University. They explain how rock weathering, as the technique is known, also could provide a circular-economy use for mining byproducts and recycled construction materials.

The benefits occur when farmers apply finely crushed basalt, found naturally in volcanic rock, onto fields. Basalt enhances the ability of soils to pull CO2 from the air and sequester it in the ground. Beerling and the researchers say it’s easy for farmers to do and would improve both the soils and their incomes.

Basalt is formed from lava that cools quickly and is compatible with existing organic fertilizer standards. It dissolves into the soil, initiating a chemical reaction that boosts the capacity for CO2 capture and storage. At the same time, it is safe for crops and delivers at least six nutrients, potassium, phosphorus and calcium among them. It also changes soil pH, making it less acidic, and that may even benefit increasingly acidic bodies of water if introduced into runoff from agricultural land.

Some silicate products recycled from the mining industry and iron and steel manufacturing, as well as waste cement from construction projects, could be processed and used in the same way. That’s a win-win for both reducing climate impacts and creating new revenue streams, and these researchers are calling on global governments to develop the rock-dust resources and access to them.

There is much work to be done before scientists are confident in how basalt dust will behave, and what the wider impacts will be. That’s why there is a 10-year project at Leverhulme to study the implications and field trials through University of Illinois Urbana-Champaign in the U.S., as well as sites in Australia and Borneo, but at the same time scientists agree there is no time to lose.

“Carbon dioxide drawdown strategies that can scale up and are compatible with existing land uses are urgently required to combat climate change, alongside deep and sustained emissions cuts,” says Beerling. “Spreading rock dust on agricultural land is a straightforward, practical CO2 drawdown approach with the potential to boost soil health and food production.”

His colleague Hansen, a former director of NASA’s Goddard Institute for Space Studies who has pressed for climate action for decades, echoed Beerling’s hopes for deployment of the rock weathering techniques.

“We have passed the safe level of greenhouse gases,” Hansen said. “Cutting fossil fuel emissions is crucial, but we must also extract atmospheric CO2 with safe, secure and scalable carbon dioxide removal strategies to bend the global CO2 curve and limit future climate change.”