For instructors who include a module on climate geoengineering, there is a very good new article in the Proceedings of the National Academy of Science of the United States on the carbon dioxide removal option of mineral sequestration, Mineral sequestration is a geoengineering approach that contemplates acceleration of the natural weathering process, producing a reaction between silicate rocks and carbon dioxide that forms solid carbonate and silicate materials. The reaction consumes one carbon dioxide molecule for each silicate molecule, with storage of carbon as a solid mineral. The PNAS article focuses on silicate weathering of the mineral olivine.
Among the article’s take-aways:
- Enhanced silicate weathering by dissolution of olivine in the humid tropics, an optimal area to effectuate this scheme, could store approximately 1 Pg of carbon per year. This is 20% less than estimated in some previous studies;
- Another complementary option would be to dissolve olivine powder in open ocean surface waters. This could increase sequestration to a maximum of 5 Pg of carbon annually. This could reduce warming by 0.6-1.1K
- The increase of riverine input of silicic acid into the world’s oceans might also enhance the marine biological pump, ultimately enhancing oceanic sequestration of carbon dioxide
- Environmental impacts need to be further assessed , including potential increases in alkalinity and silic acid in soils and aquatic ecosystems.