A new study into microbial activity when hydrogen is injected into potential underground storage sites has generated valuable findings as to where the gas could be stored in future.
There have been concerns that injecting hydrogen into subsurface porous media could stimulate enough microbial activity to consume significant volumes of hydrogen, decrease injection and recovery of the gas (by clogging pores with microbial cells and excretions) and cause corrosion of metal infrastructure.
The study found that 37 out of the 42 sites examined are at risk of microbial effects. However, despite significant microbial growth potential in these sites, microbial hydrogen consumption is likely to be “negligible to small”.
Hydrogen can alleviate a key drawback of renewable energy generation – its intermittency. However, this requires suitable temporary storage sites. Excess renewable energy can be converted to hydrogen through electrolysis (so-called ‘green hydrogen’), stored and then drawn down and turned back into electricity during periods of high energy demand.
The paper, published in Renewable and Sustainable Energy Reviews, was written jointly by scientists from the University of Edinburgh and Clausthal University of Technology, Germany. The Edinburgh researchers are part of the HyStorPor project, which is examining the feasibility of storing hydrogen in UK reservoir rocks as a means of accelerating its deployment.
The study outlines environmental controls to the growth of hydrogen-consuming microorganisms in selected depleted gas and oil fields in the British and Norwegian North Sea and the Irish Sea. Five of the 42 fields were found to have environmental conditions that impede microbial growth and are hence most suitable for hydrogen storage.
“Climate change is an urgent global problem and collaboration with international colleagues is really important to promote the implementation of hydrogen storage in porous media and help mitigate carbon emissions,” said Eike Marie Thaysen, technical research assistant at HyStorPor at the time of the study.
“This study highlights that geological storage of hydrogen at high temperatures above 122°C omits the risk for adverse microbial effects. It also indicates that there are no showstoppers for hydrogen storage in porous media with respect to microbial consumption of the stored hydrogen in fields with favourable growth conditions,” Thaysen added.
As hydrogen storage in porous media in the UK moves closer to reality, studies such as these provide important data to guide site development.
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