Modeling the release of CO2 in the deep ocean

In order to better understand the mechanics of ocean disposal of CO2 captured from power plants, a comprehensive plume model was developed to simulate the dynamic, near-field behavior of CO2 released in the water column as either a buoyant liquid or vapor. The key design variables in the model that can be controlled are: (1) release depth, zo (2) number of diffuser ports, N, and (3) initial bubble or droplet radius, ro. For a CO2 stream from a 500 MW power plant with 100% capture and zo=500 m, N=10, and ro=1 cm, the model predicts that the plume will rise less than 100 m. This will result in CO2 enrichment at depths greater than 400 m. Detailed predictions of local CO2 concentrations near the plume are presented and discussed. The issue of the residence time of the captured CO2 in the ocean is also addressed. We estimate a typical residence time of less than 50 years for releases of CO2 less than 500 m deep and, for a release depth of 1000 m, a residence time from 200 to 300 years. These residence times may be increased by releasing in areas of downwelling or by forming solid CO2-hydrates, which can sink to the ocean floor.