A multinational research team has discussed the use of finely ground silicate rock, such as basalt, in removing carbon dioxide from the atmosphere.
Led by the Laboratory for Climate and Environment Science (LSCE) and involving several researchers from the International Institute for Applied Systems Analysis (IIASA) – both based in Europe – the research spread the powder in impoverished soils and assessed the effects on carbon dioxide (CO2) levels.
Where previous studies had studied similar techniques on fertile land, the study used impoverished soil and found the largest rates of sequestration were in regions which were previously considered unsuitable for the experiment.
Basalt was a key mineral candidate and the study found up to 2.5 gigatonnes of CO2 could be removed every year, with 50 per cent due to the rock powder.
Co-author and IIASA researcher Sibel Eker explained the process.
“In a wide range of ecosystems, the fixation of CO2 during photosynthesis by plants and its storage in biomass and soils is constrained by low soil fertility,” Eker said.
“By spraying nutrient deficient ecosystems with basalt powder, which slowly releases nutrients during weathering, the nutrient constraints could theoretically be lifted, and ecosystem carbon storage promoted.”
Senior IIASA researcher and director of the Environmental Change Institute at Oxford University, Michael Obersteiner, indicated the team didn’t expect to find such positive results.
“Our findings render the global physical and economic CO2 removal potential of basalt substantially larger than previously suggested,” Obersteiner said.
As the rock powder is administered by aeroplane, the cost of carbon dioxide removal equated to about $USD150 per tonne.
The researchers suggested a number of factors which could make the process more cost- and resource-efficient.
These included increased basalt mining, low carbon deployment systems such as drones or airships, and low carbon energy sources.
“Pilot studies should focus on degraded systems and afforestation projects to test for potential negative side effects,” said lead author Daniel Goll.
“If rock powder can enhance the CO2 removal in existing managed systems, it will help to reduce pressure on natural ecosystems elsewhere.”
The study has been published in the most recent issue of Nature Geoscience.