Technical Committee Underground Storage Technology

Influence of Bio-Methane and Hydrogen on the Microbiology of Underground Gas Storage - Literature Study

The given literature review addresses possible impacts and risks of microbiological processes in underground storage facilities, with regard to the planned partial feed-in of hydrogen and bio-methane. The multiple, possible microbial metabolic pathways are presented, practical aspects of ecological parameters of reservoir microbiology, interactions with the rock matrix and formation waters, contamination risks and possible technical consequences for storage management are discussed.

Although an application transfer of experiences gained from pure hydrogen or town gas storage has certain limitations, microbiological risks associated with the intended partial feed-in of hydrogen and bio-methane into gas system can be estimated to a certain extent. Since hydrogen is an energy source for many anaerobic metabolic processes, a substantial risk potential for underground gas storages, especially porous reservoirs exists. Many underground storages in Germany provide all necessary conditions for a rapid
and complete microbial degradation process of the injected hydrogen content.
Therefore, an uncritical concentration limit for hydrogen proportion cannot be specified.

Rapid hydrogen consumption by methanogenic and sulfate-reducing prokaryotes can cause considerable technical and economic consequences, such as formation of sulfide (H2S), microbial induced corrosion (MIC) or reduction of formation permeability. The extent of possible negative effects and whether specific low-risk reservoirs exist, are currently subject to speculation. A feed-in of bio-methane is considered less problematic, if there is a way to eliminate the risk of emission of microorganisms. In view of the numerous identified risks, it seems worthwhile to consider alternatives to the direct feed-in of hydrogen into the natural gas network, such as the possibility of pure hydrogen storage in selected caverns or a prior methanisation step.