Microbial community structure and microbial activities related to CO2 storage capacities of a salt cavern

Abstract

Salt caverns are cavities that form in salt deposits and can be used for hydrocarbon or gas storage as well as waste disposal. Despite high salt concentrations in those environments, microbial life still occurs and affects the storage or disposal capacities of the cavern. In order to predict what may occur over time it is important to understand the types of microorganisms present in salt caverns and the environmental impact of their activities. For example if salt caverns were to be used for CO2 storage, the fate of CO2 will be impacted by microbial activities. In the presence of H2 microorganisms can convert CO2 to acetic acid and water or to methane and water. Samples from a salt cavern plant used to store oily sand were obtained and used to determine microbial community composition by pyrosequencing. Community analyses showed a halophilic, thermophilic community including the genera Methanohalophilus, Methanolobus and others capable of producing methane. Oil-degrading genera (Halanaerobium and Marinobacter), sulfate-reducing genera (Desulfovermiculus and Desulfovibrio) as well as the genus Acetohalobium capable of producing acetic acid in high salt environments were also prevalent. Determination of microbial activities related to CO2 fixation or transformation (homoacetogenic activity and hydrogenotrophic methanogenic activity) indicated that the salt caverns have homoacetogenic activity at both high and low salt concentration. Methanogenic activity was observed with low salt concentration only. Thus if salt caverns were to be used for CO2 storage production of acetic acid, but not of methane, is expected if H2 is present.