Naturally occurring bacteria could consume pent-up hydrogen gas in nuclear waste repositories to prevent radioactive leaks, say researchers at EPFL.
Scientists may have found an unexpected ally in the long-term disposal of nuclear waste: bacteria. In a recent study, a research team led by EPFL discovered a microbial community made up of seven species of bacteria that live naturally hundreds of meters underground in the very rock layers that have been chosen to host Swiss nuclear waste.
The Opalinus Clay formation will host geological nuclear waste repositories in Switzerland. It is expected that gas pressure will build-up due to hydrogen production from steel corrosion, jeopardizing the integrity of the engineered barriers. In an in situ experiment located in the Mont Terri Underground Rock Laboratory, we demonstrate that hydrogen is consumed by microorganisms, fuelling a microbial community. Metagenomic binning and metaproteomic analysis of this deep subsurface community reveals a carbon cycle driven by autotrophic hydrogen oxidizers belonging to novel genera. Necromass is then processed by fermenters, followed by complete oxidation to carbon dioxide by heterotrophic sulfate-reducing bacteria, which closes the cycle. This microbial metabolic web can be integrated in the design of geological repositories to reduce pressure build-up. This study shows that Opalinus Clay harbours the potential for chemolithoautotrophic-based system, and provides a model of microbial carbon cycle in deep subsurface environments where hydrogen and sulfate are present.