Gold (hydrogen) rush: risks and uncertainties in exploring for naturally occurring hydrogen

Abstract

Interest in hydrogen (H2) energy has exploded in the last few years. Much of the interest comes from transitioning to a decarbonised energy future, through the use of renewables, to convert hydrogen-rich materials (methane, water) to pure hydrogen gas streams. Each of these methods have their own challenges, such as the need for carbon capture and storage to manage carbon emissions or perspectives on the use of fresh water. At the same time as this engineered approach to generating hydrogen, there has been a quiet but exponential upsurge in research surrounding the origins and fate of naturally occurring hydrogen. Sometimes referred to as ‘gold’ or ‘white’ hydrogen, geological forms of hydrogen have been recognised for thousands of years. While already present as H2, hydrogen may exist with other gases, such as methane, helium, hydrogen sulfide and/or nitrogen. But is it real? Is it volumetrically significant, discoverable, predictable or exploitable? Early work suggests that we can begin to characterise potential sources of hydrogen, the depth ranges they may be generated from, the migration mechanisms that are relevant, and how they might be retained or lost in relation to the discovery and exploitation of this gas. However, existing publicly available data is constrained by a lack of analysis and limited evidence. While there are increased reports of seeps containing hydrogen, there is an absence of evidence of more significant finds and a lack of major analogues and case studies to date. We explore these risks and uncertainties and provide a roadmap for reducing the evidence gap.