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Natural or native molecular hydrogen (H2) can be a major component in natural gas, and yet its role in the global energy sector’s usage as a clean energy carrier is not normally considered. Here, we update the scarce reporting of hydrogen in Australian natural gas with new compositional and isotopic analyses of H2 undertaken at Geoscience Australia. The dataset involves ~1000 natural gas samples from 470 wells in both sedimentary and non-sedimentary basins with reservoir rocks ranging in age from the Neoarchean to Cenozoic. Pathways to H2 formation can involve either organic matter intermediates and its association with biogenic natural gas or chemical synthesis and its presence in abiogenic natural gas. The latter reaction pathway generally leads to H2-rich (>10mol% H2) gas in non-sedimentary rocks. Abiogenic H2 petroleum systems are described within concepts of source–migration–reservoir–seal but exploration approaches are different to biogenic natural gas. Rates of abiogenic H2 generation are governed by the availability of specific rock types and different mineral catalysts, and through chemical reactions and radiolysis of accessible water. Hydrogen can be differently trapped compared to hydrocarbon gases; for example, pore space can be created in fractured basement during abiogenic reactions, and clay minerals and evaporites can act as effective adsorbents, traps and seals. Underground storage of H2 within evaporites (specifically halite) and in depleted petroleum reservoirs will also have a role to play in the commercial exploitation of H2. Estimated H2 production rates mainly from water radiolysis in mafic–ultramafic and granitic rocks and serpentinisation of ultramafic–mafic rocks gives a H2 inferred resource potential between ~1.6 and ~58MMm3 year−1 for onshore Australia down to a depth of 1km. The prediction and subsequent identification of subsurface H2 that can be exploited remains enigmatic and awaits robust exploration guidelines and targeted drilling for proof of concept.

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Green steel – produced using hydrogen and electricity from renewable en-ergy sources – provides both the means to decarbonize steel manufacturing,and a way to facilitate growth of the international hydrogen industry. Aus-tralia, with its abundant renewable resources and ample iron-ore deposits,is in an excellent position to participate in this opportunity. We highlightthe synergies between the Australian iron-ore industry and the production ofgreen-hydrogen from renewable energy sources. We identify high-potentialareas for green steel production by cross-referencing regions of current andfuture iron-ore extraction against areas of high economic potential for hy-drogen production. From these, we select two regions, the Pilbara regionof North-Western Australia and the Eyre Peninsula in South Australia, formore detailed case studies.The analysis highlights the advantages of well-optimised generation mix(in terms of wind, solar, battery, grid-connection and salt cavern storage, etc.)in decreasing storage requirements and the resulting production costs. Wealso demonstrate that green steel production costs could be reduced furtherif the system could use grid electricity to balance onsite renewable power byparticipating in the electricity spot market and operating flexibly.

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