SEMINAR: OI Seminar Series - Dr Ian S F Jones

Dr Ian S F Jones from Ocean Technology Group, University of Sydney

Title: Enhanced Carbon Storage in the Ocean

Abstract: Nations are finding it difficult to limit the generation of carbon dioxide, and, as a consequence, the concentration of CO2 in the atmosphere is rising. This causes both heating of the Earth and acidification of the ocean. Stopping this rise in CO2 concentration requires the reduction of emissions or increase of sinks, or some of both. The ocean is a promising sink for the liberated carbon dioxide as it occupies 70% of the surface of the globe and already stores much carbon.

There are three main categories of ocean storage. They are direct injection, changes in alkalinity, and ocean fertilization. None have been commercialized at this time. Key factors examined are the storage time, the capacity, the cost and the environmental risks.

Mid-depth injection at depths of 3000 m leads to residence times greater than 500 years for 75% of the injected carbon. When carbon dioxide is injected to form a carbon lake on the sea floor, longer storage times are expected. The production of soluble bicarbonate (alkalinity change) has the longest lifetime of the three categories. Some variants of the third option, ocean fertilization, have similar storage time to mid-water injection, but have a collateral benefit of increasing the marine food web. The latter may be of the same value to humanity as the cost of providing the nutrients, and is known as a no regrets option.