“Spreading Rock Dust on Fields Could Remove Vast Amounts of CO2 from Air: It May Be Best Near-Term Way to Remove CO2, Say Scientists, but Cutting Fossil Fuel Use Remains Critical”, 2020-07-08 (; backlinks):
Spreading rock dust on farmland could suck billions of tonnes of carbon dioxide from the air every year, according to the first detailed global analysis of the technique. The chemical reactions that degrade the rock particles lock the greenhouse gas into carbonates within months, and some scientists say this approach may be the best near-term way of removing CO2 from the atmosphere.
…The rock dust approach, called enhanced rock weathering (ERW), has several advantages, the researchers say. First, many farmers already add limestone dust to soils to reduce acidification, and adding other rock dust improves fertility and crop yields, meaning application could be routine and desirable. Basalt is the best rock for capturing CO2, and many mines already produce dust as a byproduct, so stockpiles already exist. The researchers also found that the world’s biggest polluters, China, the US and India, have the greatest potential for ERW, as they have large areas of cropland and relatively warm weather, which speeds up the chemical reactions.
…Other proposed ways of pulling CO2 from the atmosphere at similar rates include using chemical solvents to capture it directly from the air, or growing energy crops, burning them to produce electricity and then burying the CO2 emissions. The new research suggests ERW will be less expensive than either and, unlike energy crops, does not compete with food for land. But the scientists said all approaches may be needed to beat the climate crisis.
…“We are calling on nations to make inventories”, said Beerling. He said mines in Northumberland, UK, that produce basalt aggregate for construction produced 20–30% waste dust. But he said some mining specifically to produce basalt rock dust would probably still be needed, using existing mine capacity rather than new mines. Beerling said ERW did not require new technology, and farmers could get behind it, adding: “If you could demonstrate to farmers in China and India, for example, that they are going to get crop yield increases and get paid $100 a tonne for removing CO2, then it becomes really attractive.”…Beerling said that while the model used for the analysis was sophisticated, it would be important to compare its estimates with real-world experiments under way on 4ha plots in the UK, US, Australia and Malaysian Borneo, and that more research was needed on the detailed soil chemistry. “It is quite a young science”, he said.