Field trials have shown that carbon is stored in the soil even in dry climates.
Adding crushed volcanic rock to farmland could play an important role in removing carbon from the air. Scientists from the University of California, Davis and Cornell University found in field studies that the technology stores carbon in the soil, even during California’s extreme drought.The study was published in the journal environmental research communication.
As it falls, rain picks up carbon dioxide from the air and reacts with volcanic rocks, trapping the carbon. This process, called rock weathering, can take millions of years and is too slow to offset global warming. However, crushing rocks into fine dust accelerates their weathering.previous the study Researchers estimate that if this “enhanced” rock weathering spread to agricultural land around the world, 215 billion tonnes of carbon dioxide could accumulate over the next 75 years.
However, until now this technology had not been field tested in dry climates.
“These reactions require water,” said lead author Iris Holzer, a doctoral candidate in soil and biogeochemistry in the Department of Land, Atmosphere, and Water Resources at the University of California, Davis. “We are interested in the potential for global carbon storage through enhanced weathering, so to understand whether it works in these drier climates and whether different measurement approaches are effective. We were excited to be able to observe carbon removal in this environment.”
California Drylands: A New Frontier in Carbon Storage
The researchers applied both metabasalt and olivine crushed rock to five acres of fallow cornfields in the Sacramento Valley. They collected measurements during the winter of 2020-2021. At the time, California was experiencing an extreme drought, with precipitation reaching 41% of the historical average.
The study found that plots that used crushed stone stored 0.15 tons of carbon dioxide per hectare (2.47 acres) compared to plots that did not use crushed stone during the study. If this amount of carbon were removed from all of California’s farmland, it would be the equivalent of removing 350,000 cars from the roads each year, although researchers expect weathering rates to vary depending on the environment. .
Impact and future directions
“We definitely see evidence of weathering processes occurring over a short period of time,” Holzer says. “Even infrequent heavy rains in the West may be enough to accelerate rock weathering and remove carbon dioxide.”
Holzer said the next challenge is to measure and verify large-scale carbon storage and track it over time.
41% of the Earth’s surface is covered by dry land, which is expanding due to climate change. The researchers said this makes investigating accelerated weathering of rocks in drylands increasingly important.
“When it comes to bending the world’s carbon curve, we are in a race against time,” said lead author Benjamin Z. Houlton, Ronald P. Lynch Dean of Cornell University’s College of Agriculture and Life Sciences. . “Our study presents a new way to validate carbon removal through enhanced weatherization. This is an important step forward for scaling this technology in agricultural lands around the world.”
Reference: “Direct Evidence for Atmospheric Carbon Dioxide Removal Through Enhanced Weathering in Agricultural Soils,” by Iris O. Holzer, Marika A. Nocco, and Benjamin Z. Houlton, October 18, 2023. environmental research communication.
Other authors include Mallika Nocco of the University of California, Davis’ Office of Land, Air, and Water Resources;
This research was funded by the California Strategic Growth Council and the Grantham Foundation’s Roger Santo and Doris Matsui as part of the Working Lands Innovation Center. His SGI, Standard Industries’ aggregates and mining company, donated crushed metabasalt from its site in Ione, California.