Basalt powder in cropland may be a financially viable answer to climate change

This Tuesday, scientists from the American Geophysical Union announced in that adding pulverized volcanic rock to farmed fields could increase carbon sequestration to within the IPCC’s recommended levels by 2080 while also improving soil quality.

The process is called enhanced rock weathering. Precipitation absorbs carbon dioxide from the air, rendering the raindrops mildly acidic. The acidified interacts with the basalt in the soil to form carbonates, which eventually reach the ocean. Once there, the carbonates may also reduce the acidity of the ocean. The authors of the study recommend silicates, especially basalt rock, because they weather quickly. The study authors say this is the same thing that would happen to all human-induced carbon emissions eventually, just sped up to the point where it could actually help.

“Enhanced rock weathering poses fewer risks compared to other climate interventions,” team leader S. Hun Baek said in a press release. “It also provides some key benefits, like rejuvenating depleted soils and countering ocean acidification, that may make it more socially desirable.”

The research team focuses heavily on what they call “realistic implementation.” The study showed that the technique would have the greatest impact when used on tropical farms because the hot, wet conditions cause weathering to proceed more quickly. Researcher Noah Planavsky, also of Yale, pointed out that farmers already add pulverized calcium to their fields regularly, so some of the necessary infrastructure may already be in place.

The researchers used Soil Cycles of Elements simulator for Predicting TERrestrial regulation of greenhouse gases (SCEPTER), a 1-D reactive transport modeling system, to create predictions for over 1000 agricultural sites in different parts of the Earth from 2006 to 2080. Tropical farmland showed the greatest amount of carbon sequestration per unit because the hot weather and high moisture levels caused weathering to proceed more quickly.

According to the study, if 10 tons of pulverized basalt per hectare were applied to all the planet’s farmland, enhanced rock weathering would remove over 215 gigatons of carbon from the atmosphere over 75 years, especially if placed on farms in tropical areas. If applied only to the sites used for the simulation, 64 gigatons.

The study was funded by Yale University’s Department of Earth and Planetary Sciences.

Read the full study in the open-access journal Earth’s Future.

Baek SH, Kanzaki Y, Lora JM, Planavsky N, Reinhard CT, Zhang S. Impact of Climate on the Global Capacity for Enhanced Rock Weathering on Croplands. 14 August 2023. Earth’s Future. 11(8). doi: 10.1029/2023EF003698