Crushed basalt being spread in a field trial of enhanced rock weathering for carbon dioxide removal in Queensland, Australia Paul Nelson Spreading crushed silicate rocks like basalt on fields could remove up to 1.1 billion tonnes of carbon dioxide from the atmosphere annually while increasing crop yields, according to an analysis of the method’s global potential. But some researchers question whether that figure is really achievable. Known as enhanced rock weathering, this technique accelerates the breakdown of rocks by rainwater, a natural process that, over millions of years, has transferred CO2 from the atmosphere to the ocean and helped cool the planet in hothouse-Earth periods. Farmers have been spreading ground limestone on fields for centuries to improve nutrient uptake in crops. “The main benefit is through sort of solving atmospheric CO2 through chemical reactions,” says Chuan Liao at Cornell University in New York. “And there are also some side benefits, such as adding… magnesium, calcium potentially, to supplement soil nutrients.” As emissions continue to increase, the United Nations climate body has said humanity will require …