Energy Systems of the Future

Geological Hydrogen – An Overlooked Energy Source?

For the transition toward a climate-neutral energy system and industry, large quantities of low-carbon molecular hydrogen will be required. With the development of "green" and "blue" hydrogen taking more time than initially hoped, another form of hydrogen has gained increasing attention: geological hydrogen.

Geological hydrogen encompasses two forms: Natural hydrogen (also referred to as white or golden hydrogen) is molecular hydrogen of geological origin, formed by natural processes in the Earth's subsurface, such as reactions between certain rock types and water. Under the right geological conditions, it may accumulate as subsurface deposits. Interest in natural hydrogen was largely triggered by the discovery of a hydrogen accumulation near the village of Bourakébougou in Mali, which became the first known site where natural hydrogen was extracted and used for electricity generation. Since then, scientific publications have increased significantly, and both start-ups and major energy companies have begun exploring its potential. Exploration licenses have been granted in countries including France, Spain, Finland, the USA, Canada, Australia, China and Russia.

Stimulated hydrogen (also referred to as orange hydrogen) takes a different approach: instead of searching for naturally occurring deposits, water or catalysts are injected into iron-rich rock formations to deliberately trigger hydrogen-generating reactions underground. The generated hydrogen is then extracted from the recirculated fluid. Research has so far been largely limited to laboratory experiments, and commercial deployment is likely decades away. This paper focuses primarily on natural hydrogen.

→ More on stimulated hydrogen

While the topic is increasingly discussed within the geosciences, it has so far received little attention from experts in energy technology, energy systems analysis, and energy economics. Public awareness remains limited as well. Nonetheless, political decision-makers in several countries have expressed high expectations. At the European level, the European Strategy and Policy Analysis System (ESPAS) states in its Global Trends Report 2024 that "the possibility of mining natural hydrogen deposits has potential for a future energy revolution." In Germany, however, natural hydrogen has so far attracted relatively little attention in both policy and research.

This discussion paper by the Academies' Initiative ESYS aims to provide an overview of the current state of scientific knowledge on geological hydrogen, identify key uncertainties, and assess the potential role of natural hydrogen in the transition of the energy system and industry. The findings are based on interviews and a workshop with international experts, supported by a literature review.

Generation

Deep within the Earth, several chemical reactions can produce hydrogen. But for it to become a usable resource, hydrogen must accumulate in suitable rock formations without being lost along the way.

Where Is the Search Underway?

The rock types capable of generating hydrogen are relatively widespread across all continents. In recent years, exploration activities have increased markedly worldwide.

To date, most mapping efforts have been largely empirical, relying on the compilation of reported hydrogen occurrences. Since hydrogen was not actively looked for, the data often stems from gas samples taken during oil and gas exploration or mining activities. A limitation of this approach is that promising regions may be overlooked due to a lack of data. Moreover, in most cases only the hydrogen concentration is reported, but elevated concentrations alone do not demonstrate the presence of a sustained subsurface accumulation or an economically recoverable resource. Recently, there has been a shift toward predictive mapping, including geological and geophysical data and modelling of hydrogen generation, transport pathways and accumulation. The European Commission has published a call for tender requesting the mapping of natural hydrogen resources in the EU. If, where and when the search for natural hydrogen accumulations will eventually be successful remains to be seen. Moreover, whether accumulations are actually economically viable depends on factors that go well beyond geology alone.

Use Cases

The economic viability of natural hydrogen can be substantially improved if it is produced jointly with other valuable resources (co-production) or if costly transport is avoided. Since building extensive pipeline infrastructure will take many years and most deposits may be relatively small, decentralised use cases with local consumption are regarded as the most promising in the near term.

Conclusions and Outlook

Geological hydrogen has attracted growing attention from researchers, start-ups, and energy companies worldwide. The prospect of a potentially low-cost, low-carbon hydrogen source is compelling — but the current state of knowledge is still characterised by substantial uncertainties. This paper draws the following conclusions and identifies measures to facilitate research and exploration and thereby improve the knowledge base.

• 1

  Existence of exploitable deposits remains uncertain

  To date, no large-scale mineable deposit of natural hydrogen has been identified anywhere in the world. While the mechanisms of hydrogen generation are relatively well understood, critical gaps remain: how hydrogen migrates through the subsurface, whether and where it accumulates in sufficient volumes, and how much is consumed by microbes along the way. Much of the publicly available data comes from company reports rather than peer-reviewed studies, which makes independent assessment difficult. Most experts nonetheless consider it likely that exploitable deposits exist — their discovery would be the single most important milestone for the field.

• 2

  Decentralised use cases are the most plausible near-term contribution

  If commercially viable deposits are found, production costs will depend heavily on site-specific factors such as flow rate, hydrogen concentration, depth, and proximity to offtakers. Under favourable conditions, costs could be competitive with other low-carbon hydrogen sources. Most experts see the most realistic near-term application in decentralised energy supply — for example, providing power to remote mining operations in geological settings where hydrogen and valuable minerals co-occur. A role as a large-scale pillar of the global hydrogen economy is considered less likely by most; natural hydrogen is more plausibly one piece of the puzzle rather than a real gamechanger.

• 3

  The hope for natural hydrogen must not distract from the expansion of other energy transition technologies

  Given the current level of uncertainty, it cannot be taken for granted that natural hydrogen can make a decisive contribution to the transition to net-zero emissions. Green hydrogen and electrification must be scaled up regardless. Only if large, economically exploitable deposits are confirmed and their environmental performance proven should natural hydrogen be integrated as an additional element in long-term transition strategies.

Low-Regret Measures

The following measures can help build a better evidence base and reduce barriers to exploration — without prematurely committing to natural hydrogen as a strategic resource.

• 1

  Clarify the legal status of natural hydrogen

  Legal frameworks in many countries do not yet explicitly permit the exploration and extraction of natural hydrogen. In Germany, recognising hydrogen and helium as freely mineable raw materials — as announced in the Hydrogen Acceleration Act — would remove the requirement for landowner consent and substantially reduce costs and administrative effort for exploration companies.

• 2

  Fund research to fill critical knowledge gaps

  Public funding for research into geological hydrogen systems can help to build a better knowledge base for informed policy decisions. Independent, scientifically validated data are needed — particularly on migration pathways, microbial consumption, and the interpretation of measured data. Knowledge gained also has synergies with underground hydrogen storage technology, which is relevant for the broader energy transition regardless of natural hydrogen's potential.

• 3

  Environmental performance must be rigorously assessed

  Natural hydrogen is not automatically carbon-neutral. Comprehensive life cycle assessments are indispensable. In particular, methane leakage during extraction would significantly worsen the climate balance, and indirect climate effects of hydrogen emissions are not yet well understood. To qualify as a low-carbon fuel under frameworks such as the EU Renewable Energy Directive, the carbon balance must be accurately assessed. Initial estimates suggest that natural hydrogen from high-concentration deposits could have a climate footprint comparable to green hydrogen — but this may strongly depend on site conditions and needs further investigation.