Hydrogen is emerging as a low-carbon fuel option for transportation, electricity generation, manufacturing applications, and clean energy technologies that will accelerate the United States’ transition to a low-carbon economy. However, a key challenge is to ensure the safe and effective storage of hydrogen. One of the primary unknowns in H2 storage is the impact caused by microbial communities that are naturally present in underground reservoirs at a broad range of conditions. H2 is known to be an energetic electron donor, supplying energy for a wide variety of subsurface microorganisms, many of which have been documented to exist naturally in the geologic units that are targets for H2 gas storage.

Major expected microbial driven reactions are:

  • Methanogenesis: In this reaction, microorganisms called methanogens oxidize hydrogen and reduce carbon dioxide to produce methane. Gaz de France previously found the microbially induced methanogenesis reaction to rapidly transform 50% of stored hydrogen gas into methane.4
  • Hydrogen Sulfide Production: A hazardous mechanism of H2 consumption might occur through sulfate and sulfur reducers (SRBs). Gaz de France, documented technical challenges associated with SRBs producing hydrogen sulfide gas (H2S). Town gas storage fields (~ 45-60% H2) in the Czech Republic have reported significant consumption of stored H2 coupled to H2S production. Lastly, several models demonstrate reservoirs that are current targets of hydrogen storage have a high risk of H2S production from SRBs.
  • Microbiological Corrosion: Microbially induced corrosion of steel has previously been found extreme in the anoxic environment created by the introduction of H2 to the subsurface. Hydrogen-consuming microorganisms have been implicated in causing corrosion at temperatures up to 90 °C and high salinities. The natural gas leak of 2015 at the Aliso Canyon facility was ultimately attributed to microbially induced corrosion of a well casing.
  • Secondary Effects: The shifting microbial community may lead to other unexpected byproducts, such as organic acids or even calcium carbonate scaling. The presence of microbial communities adapted to reducing, H2-rich environments may contribute to corrosive mineral reactions through local pH changes and co-production of various acids.

Large-scale hydrogen storage will not be possible without the delineation of expected microbial activity in these systems. Before hydrogen can be safely and securely stored in underground reservoirs, the effect of gas injection on the naturally occurring microbial community and the associated change in chemistry needs to be assessed. NETL is currently researching several targeted hydrogen storage formations for the risk of microbial consumption of H2; work is ongoing using the subsurface microbial communities and high-pressure-high-temperature simulation experiments to demonstrate biogeochemical changes that can be expected during subsurface hydrogen storage.