Options for enhancing the storage of carbon dioxide in the oceans: A review

Abstract

The various proposed options for enhancing CO 2 storage are often ingenious but rarely feasible. Fertilizing the central gyres would require enormous amounts of N and P fertilizer. Addition of iron to the Southern Ocean has been rejected as inefficient. The deep sea disposal of 50–100% of fossil fuel CO 2 would suppress the predicted transient peak of atmospheric CO 2 but eventually the atmospheric CO 2 level will be the same as without, unless rapid buffering by dissolution of calcite is significant. Ocean disposal applies only to point sources representing ∼30% of fossil fuel emissions; relocation of these plants to maritime regions may not be economical either. Also ocean disposal costs ∼30–45% of the energy produced. Current research is focusing on production and oceanic mixing behaviour of the effluent stream (this volume). In this paper the fate of the disposed CO 2 is assessed. The various proposed forms appear chemically unstable relative to ambient seawater. However the higher CO 2 contents of seawater might lead to part of the CO 2 being buffered forever through enhanced dissolution of existing calcite deposits. The predicted impact depends on the selected rate constant of latter dissolution. Ocean dumping is a fallback option, in case the sensible options of energy conservation and shifting to other energy sources would not be implemented adequately. Latter options would require societal and economic adaptations but appear the most efficient, if not inevitable, policy for imminent reduction of CO 2 emissions.