Permanent storage of carbon dioxide in the marine environment: The solid CO2 penetrator

To circumvent the uncertainty related to presently studied ocean disposal options based on pumping of liquid carbon dioxide or hydrate slurry injection at depth, with the associated risk of short term physical and biological oceanographic processes returning an important fraction of it to the atmosphere, a disposal technique using the natural geochemical storage properties of deep marine (carbonate or alumino-silicate rich) sedimentary formations is suggested. The technique proposed would depend on the fact that carbon dioxide can be obtained as a solid by cooling to -78.5 degrees C. The overall density is approximately one and a half times similar to 1.56 kg.dm(-3) that of seawater. If the solid was shaped as a torpedo and then left to fall through the water column it would penetrate quite deeply into soft underlying sediments. This conclusion is based on in-situ investigations using penetrators that were studied as a disposal option for other solid wastes. This concept should, therefore, provide permanent storage as the emplaced carbon dioxide will be chemically sequestered by the sediments (via the formation of an intermediate clathrate). Other than secure segregation of the emplaced CO2, the penetrator option has a further major advantage in that there should be no long-term effects to biological systems: penetrator disposal is deep within sedimentary formations which have zero or very low biological activity.