A benign form of CO2 sequestration in the ocean

It is proposed that liquid CO2 is mixed with pulverized limestone (CaCO3) and seawater in a pressure vessel. An emulsion is created which is piped to intermediate depth in the ocean, where the emulsion is released through a diffuser. The emulsion plume has a bulk density of 1.4 kg m(-3), thus it will sink as a gravity current to greater depth from the release point. Several kinetic processes occur simultaneously: (a) the entrainment of seawater by the emulsion plume, (b) the dissolution of CaCO3, (c) the dissolution of CO2, and (d) the reaction of dissolved CO2 with CaCO3 to form bicarbonate. In the presence of CaCO3, the plume around the release point has a pH 5 instead of 3 around the release point of liquid CO2. Subsequent entrainment of seawater brings rapidly the pH to near ambient values. The resulting calcium and bicarbonate ions are available nutrients for marine organisms. The bicarbonate solution will stay in the ocean indefinitely as contrasted with carbonic acid which eventually would resurface and equilibrate with the atmosphere. Most importantly, the emulsion can be released slightly below 500 in, as the emulsified CO2 will not phase-separate and ascend to a depth where it would flash into vapor. This makes the release depth accessible to many more coastal power plants than the previously thought minimum depth of 1000 in for the release of pure liquid CO2.