Environmental Impact Assessment of Carbon Storage Using a CO2 Bubble Model

Abstract

Carbon storage in underwater geological structures is considered as a way of mitigating global climate change. One of the environmental issues related to carbon storage is the leakage of carbon dioxide from the storage. A model for tracking CO2 bubbles in the water column has been developed to assess the environmental impact of CO2 leakage from a shallow site that is under consideration in Korea. The dependences of the rising velocity and the solubility to bubble size are taken into account while assuming spherical bubbles of from 0.1 mm to 18 mm in diameter. Since the study area is a shallow water environment (similar to 170 m), leaked CO2 bubbles reach the surface within 20 minutes during which the local horizontal currents transport the bubbles less than 500 m. While rising to the surface, less than about 2x10(-7)% of leaked CO2 is dissolved into seawater. The remaining amount is released into the air. If it is assumed that 1x10(5) ton of CO2 is leaked as bubbles, the pH of seawater that is influenced by the CO2 bubbles at the absence of ocean currents would be lowered by less than 0.01 on the average. If the lateral dispersion of the bubbles by ocean currents is considered, the effect would be smaller.