Potential Methods for Dispersal of Precipitated Calcium Carbonate for Solar Radiation Management

Abstract:

Direct introduction of aerosols into the stratosphere is one of the SRM techniques proposed to effect climate modification. Although sulfates are most frequently mentioned as likely aerosol materials, a group at Harvard has proposed using finely divided calcite (calcium carbonate), suggesting that this material will efficiently scatter incoming sunlight, reduce lower stratosphere heating and chemically reduce or reverse ozone depletion.

Finely divided calcium carbonate is notoriously difficult to disperse. We have investigated dispersal of commercially available precipitated calcium carbonate (PCC) having a nominal mass distribution that peaks at 0.7 µm. Two techniques, aerosol spraying of crudely fluidized PCC using a compressed air-powered nozzle, and release of a suspension of PCC in liquid carbon dioxide through a simple valve, have been investigated. Both give aerosols with particle size distributions very similar to that of the bulk material. The latter method would appear to be suitable for small-scale experiments, while the former might scale up well, should full deployment ever be needed.