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The extraction of natural hydrogen from the bowels of the earth is today considered a very promising area in renewable energy. Hydrogen is expected to solve a large range of industrial and environmental problems, including energy storage and reducing emissions from heavy transport. The original idea was quite simple: produce green hydrogen by electrolysis using electricity generated by solar stations or wind generators, store the hydrogen for the required time in a compressed or liquefied state, transport it to the place of consumption, and then convert it back into electrical energy using fuel cells or burn it in special boilers or turbines for generating thermal energy.
Everything looked logical, and it was assumed that the existing barriers would be successfully resolved. However, the problems of the high cost of electrolysis or the technological difficulties of transporting hydrogen do not yet allow it to reach the level of its commercial use. As before, hydrogen obtained as a result of high-temperature reforming of methane (gray hydrogen) looks commercially cheaper and realistic in terms of production volumes for industrial needs. But the problem here is different, and it is related to the use of fossil fuels and serious carbon dioxide emissions. However, even if CO₂ burial is used, such hydrogen (blue) remains out of competition with green hydrogen from renewable sources. the hydrogen market (merchant), for example, in the USA on the Gulf Coast, where a cluster of independent hydrogen producers has been created for the needs of oil refining, including pipeline transportation of hydrogen.
According to IEA, the world produced approximately 95 Mt H₂ in 2022, of which fossil fuels accounted for 83% (methane, coal). Another 16% was received as part of the by-product. Obviously, such technologies do not meet the ideal requirements of hard-line climate change advocates. However, electrolysis accounted for only 0.1% of the total amount of hydrogen produced, and CO₂ storage (CCUS) is used in another 0.6% of cases. Those the promotion of environmentally advanced hydrogen production technologies has encountered so far insurmountable obstacles. In such a situation, natural or white hydrogen seems to be the most acceptable solution for all stakeholders.

For a long time, the only clear example of the presence of white hydrogen in the earth’s crust was the small village of Bourakébougou in Mali, where back in the late eighties of the last century, while drilling a water well, drillers stumbled upon a stream of almost pure hydrogen. This hydrogen was later used through a generator to generate electricity. Thus, for the first time, a technological scheme was organized for the production of energy from natural hydrogen with a productivity of approximately 5 tons of hydrogen per year (98% hydrogen, 1% methane and 1% nitrogen), and not anywhere in highly developed countries, but in Africa, far from energy delights. To date, 13 hydrogen-containing wells have been drilled and tested in this region over a five-by-five-kilometer area.
Later, additional evidence of the presence of underground reserves of white hydrogen appeared in the USA, Australia, Albania, Spain, Oman, France and some other countries. Today, several dozen startups are actively involved in exploratory drilling, and well-known investors have stepped up.
American startup Koloma last year raised $91 million from funds such as Bill Gates' Breakthrough Energy Ventures. Natural Hydrogen Energy has drilled an exploration well in Nebraska. “It will take a couple of years to reach commercial production,” said Viacheslav Zgonnik, CEO. Australian Gold Hydrogen, based on geological data dating back almost a century, carried out drilling operations in 2023 and discovered flows of hydrogen with a purity of up to 86%, as well as helium with a purity of up to 6.8%. Another Australian company, Hy Terra, is trying to implement the Nemaha Project in Kansas, USA.

Among recent developments in this field, mention should be made of the discovery of a spontaneous flow of hydrogen at a chromite mine in Albania. However, the most important result of these searches was the discovery last year of a hydrogen deposit in the Lorraine region in the southeast of France. Here, geologists, while searching for coalbed methane in an old coal region, discovered huge underground reserves of hydrogen, the volume of which is estimated at 46 million tons. The percentage of hydrogen in the gas extracted from a depth of 1100-1250 meters was 15-20%. Of course, all this information needs detailed verification and qualitative assessment. In any case, this event is more than just a worthy fact; perhaps it will become a serious catalyst for the very attitude towards this problem. It is possible that this will lead to a massive influx of new researchers, drillers and investors, as well as oil and gas companies to form the basis of white hydrogen production technology.
An additional incentive for this process is the optimistic estimates of the world's reserves of natural hydrogen, which are still made at a preliminary level. Thus, according to the Financial Times, USGS research geologist Geoffrey Ellis reported that underground reservoirs around the world contain about 5 trillion tons of hydrogen. This is a huge figure, even if it is possible to extract only a small part of these reserves.

How and where to find natural hydrogen

To date, successful discoveries of natural hydrogen have been the result of chance, luck, or, at best, professional intuition. There is no detailed and recognized scientific methodology for the geological distribution of natural hydrogen yet. As a matter of fact, there are no reliable and proven tools for the practical assessment of geological structures containing hydrogen. All this is in development. Of course, there are general ideas, concepts and forecasts.
According to one version, the formation of hydrogen is possible during the process of serpentinization. This process is based on the hydration of basic rocks under the influence of thermal aqueous solutions. In particular, ultramafic rocks composed of olivines (Mg₂SiO₄, Fe₂SiO₄), which have a strong tendency to react with water. In this case, for example, iron-containing olivines during such interaction form free hydrogen according to the following mechanism:



Forsterite, an olivine mineral. Groundwater interacting with olivine can result in hydrogen building up in the surrounding rock layers.
Public Domain. Image and specimen from Smithsonian National Museum of Natural. Source: USGS

For this process, the optimal temperature has been determined in the range of 200-310^oC. Obviously, hydrogen production in such a system will depend on the amount of active rock. The flow of hydrogen to the surface will also be largely determined by the permeability of the near-surface layers of the earth's crust. Thus, the presence of iron-bearing olivines in combination with thermal waters in geological rocks can serve as a serious indication of the presence of free hydrogen. However, as shown in the work Diffused flow of molecular hydrogen through the Western Hajar mountains, Northern Oman, hydrogen flows are also found from geological formations structurally located below the serpentinites.
Another option for the formation of natural hydrogen is based on the processes of aqueous radiolysis. As a result of the radioactive decay of uranium, thorium, etc. energy is generated leading to radiolysis, i.e. to the breakdown of water into oxygen and hydrogen molecules. According to the researchers, the amount of molecular hydrogen produced is proportional to the porosity of the rock matrix filled with water. In such a model, where hydrogen is present, oxygen should also be present, which, however, has not been confirmed.
Other options for the formation of natural hydrogen include biological processes, as well as Volcanic Reactions and Hydrothermal Processes. In the first case, it is assumed that hydrogen gas is formed from organic substances, primarily from natural gas, through biological activities, for example, through fermentation, anaerobic decomposition, etc.

The largest amount of hydrogen belongs to Deep-seated Hydrogen. This is indirectly confirmed by an increase in hydrogen concentration with increasing drilling depth. In particular, this was reported by researchers in the Lorraine region in France. So at a depth of approximately 1100 meters the hydrogen concentration was 15%, at a depth of 1250 meters – 20%. Concentrations close to 100% are expected, according to researchers, at a depth of 3000 meters. Perhaps this option is the most difficult to understand and therefore causes much controversy.
Less frequently mentioned are other options for the formation of hydrogen, in particular the contact of water with recently exposed rocks, the decomposition of accumulations of organic substances, and the release of hydroxyl ions in minerals. The Natural Hydrogen Energy LLC website gives the following examples of the levels of detected natural hydrogen in some countries: Turkey - 12% H₂; Iceland – 24% H₂; Japan 51% H₂; Oman 82% H₂; USA 96% H₂.

The current challenges of creating a valid and convincing system for estimating the hydrogen content of geological strata are largely due to the historical neglect of hydrogen identification in the analysis of gases from drilled wells. This was due both to the lack of adequate gas analyzers and to the lack of formulation of the hydrogen accounting problem itself.
For example, The occurrence and geoscience of natural hydrogen: A comprehensive review provides the following data: “The United States Geological Survey (USGS) Energy Geochemistry Database (EGDB) contains 103,000 records of gas samples from around the world, with only 8 cases hydrogen was detected at a concentration of >10%.”

Probably, expanding research and clarifying the state of specific hydrogen-containing formations will make it possible to create practical geological maps by analogy with geological models in oil and gas production. Of course, in this case, seismological, gravitational or electromagnetic methods of exploration of oil and gas fields will certainly be useful. But in any case, new specific methods and instruments for measuring gases in underground layers are needed, such as, for example, hydrogen gas probes, which are unique spectrometers for measuring and analyzing dissolved gases in deep wells.

Here it is also very important to identify and systematize the list of accompanying natural signs accompanying the presence of hydrogen. Some of them may have unconventional approaches. For example, U.S. Geological Survey (USGS) is developing hydrogen exploration methods based on the assumption of an association between hydrogen and noble gases. A similar approach is used by Natural Hydrogen Energy LLC, Gold Hydrogen, and Hy Terra, which drill to find accumulations of hydrogen and helium.

The work Natural Molecular Hydrogen Seepage Associated with Surficial, Rounded Depressions on the European Craton in Russia states that “...In the Russian part of the European craton, several thousands of subcircular structures ranging in size from a hundred meters to several kilometers in diameter have has been identified throughout the region extending from Moscow to Kazakhstan. Generally, these structures correspond to minor morphological depressions".
There is extensive evidence of hydrogen signatures in geothermal brines and non-ferrous metal mines.

Below is an explanatory diagram from the USGS that visually summarizes the current understanding of natural hydrogen.



How hydrogen forms underground. Public Domain. Image courtesy of Science. Source: USGS

Based on the analysis, we can conclude that most often researchers and drilling companies rely on the model of hydrogen formation as a result of the interaction of iron-containing olivines with thermal waters, as well as on the presence of helium in the hydrogen-containing flow. The main research tools are modern gas analyzers.
However, the overall situation can be summed up in the words of one US Department of Energy director: “They're drilling haphazardly now.”

What is hydrogen used for

It would seem a rhetorical question. But still. First of all, hydrogen has always been considered as a renewable, inexhaustible and environmentally perfect resource for energy needs. Potentially, hydrogen can be burned to produce thermal energy and used as fuel in fuel cells to generate electricity. In addition, hydrogen has long been seen as a means of storing energy from renewable sources. However, the actual results of using hydrogen in the energy sector are very modest, except for its large-scale use in oil refining to remove sulfur from crude oil or petroleum products.
Let us remember in passing that the mass heat of combustion of hydrogen is almost 2.5 times greater than that of methane. However, the density of hydrogen is more than 8 times less than the density of natural gas. Therefore, the volumetric heat of combustion of hydrogen is significantly less than that of methane. As a result, to achieve the same energy conversion rates, it is necessary to transfer through the transport system a volume of hydrogen approximately three times greater than the volume of methane. Further, hydrogen has the smallest atomic size of all elements and very high chemical reactivity.



Hydrogen Tools/ Basic Hydrogen Properties/ https://h2tools.org/hyarc/hydrogen-properties

The burning rate of hydrogen is higher than natural gas. The propagation speed of a laminar hydrogen flame is 10 times higher than that of natural gas. Hydrogen has a low flame activation energy. These, as well as several other parameters, demonstrate the serious advantages of hydrogen over natural gas, but it is much less often mentioned that these same indicators also give rise to serious problems. Thus, when pure hydrogen interacts with most metals, hydrogen embrittlement occurs. When burning hydrogen, there is a possibility of flame propagation upstream (flashback) with the possibility of spontaneous combustion.

As for the environmental benefits of hydrogen, not everything is clear here either. For example, when burning hydrogen as part of a methane mixture, a 10% reduction in CO₂ emissions is achieved at a hydrogen concentration of more than 20%, and a 50% reduction in CO₂ only when the hydrogen concentration in the mixture is already approximately 70%. Since the combustion temperature of hydrogen exceeds 2000^oC, there is a high probability of the formation of nitrogen oxides, the greenhouse activity of which is approximately 300 times higher than that of carbon dioxide. Usually, the issue that when using hydrogen, both in combustion technology and in fuel cells, is not considered at all, there is a serious increase in the formation of the main greenhouse gas - water vapor. Although it is excluded from accounting in the Kyoto Protocol, in the case of using hydrogen on a mass scale, this problem can no longer be hidden.

In many countries, and especially in Germany, it is planned to use hydrogen as part of methane mixtures in existing gas supply systems (Power-to-gas Technologies). Taking into account the high calorific value and corrosive activity of hydrogen, its concentration in methane mixtures is in most cases limited to 5-6% (Injection limits).

Another option for using hydrogen is to produce thermal energy through direct combustion of hydrogen. Thus, one of the leaders in boiler equipment, the German company Viessmann, states that Vitodens condensing boilers can easily operate on a mixture of up to 30 percent hydrogen. By 2025, the company intends to produce boilers that can run on 100 percent hydrogen without CO₂ emissions (hydrogen-boilers). BDR Thermea Group and many other companies are moving in the same direction. How the problem with nitrogen oxides will be solved is not reported. The UK government has gone further and pledged to ban the installation of fossil fuel heating systems in new homes from 2025.

Combustion of a hydrogen-containing mixture in gas turbines is also used. Here General Electric has made the greatest progress. Its GE 7F turbine allows the use of up to 65% hydrogen capability in the gas mixture. About a thousand such turbines are successfully operated in 11 countries around the world. However, there is no information on the percentage of hydrogen in the gas mixture in the practical use of these turbines.


Silver tanks with smokestacks. Envato Elements. 4ZCUM5AXW9

Siemens-Energy presented the SGT-800 turbine, which allows up to 75% hydrogen in the gas mixture. Japanese Kawasaki has successfully tested the H₂ Micro Mix combustion chamber in demonstration mode for burning 100% hydrogen (H2 Micro Mix combustion chamber). Emissions of nitrogen oxides (NOx) did not exceed 50 ppm (16% vol. O₂). In April 2023, Korean companies Hanwha Impact and Hanwha Power Systems, in collaboration with Korea Western Power, successfully demonstrated 60% hydrogen mixing in the same 80 MW class gas turbine. However, nitrogen oxide (NOx) emissions were confirmed below 9 ppm without any additional reduction devices. Already in December, the company reported the successful testing of its turbine with 100% hydrogen content. Similar research aimed at co-combustion of hydrogen and methane is being carried out by the Japanese Mitsubishi Power. Its diffusion combustion technology with preliminary mixing of hydrogen and air through special swirlers allows the use of mixtures with a 30% hydrogen content with the prospect of up to 100%. This technology can significantly reduce the emission of nitrogen oxides.

The most promising direction for using hydrogen in the energy sector is fuel cells. The main advantages of fuel cells most often include the possibility of direct generation of electricity both in stationary conditions and in transport or in portable devices, as well as the absence of harmful emissions, excluding water vapor. However, this places increased demands on the quality of hydrogen. In addition, the production of thermal energy is difficult. As for the fuel cells themselves, it should be noted that they are still relatively low-power and difficult to operate.

So, it is obvious that hydrogen has broad potential applications in the energy sector. However, to do this, it is necessary to solve a number of difficult engineering issues, including, first of all, the development or selection of the optimal technology for hydrogen production, as well as its transportation and storage from the available set of options.

How to use natural hydrogen

Unlike the current scheme for using hydrogen through electrolysis or methane reforming, when hydrogen production is close to the consumer, natural hydrogen in the vast majority of cases will not be produced at the point of consumption. Of course, the example of the use of natural hydrogen in a small African village in Mali does not count in this case.

In order to present a hypothetical scheme for the use of natural hydrogen on an industrial scale, the following must always be taken into account:

- What is the composition of the produced natural hydrogen?

Approximate reference points here could be 5-10%; 10-70% and more than 70%. If the share of hydrogen in the extracted mixture is 5-10%, and the rest is natural gas (excluding other gases), then the most obvious use of such a gas mixture will be to send it to industrial gas pipelines. If the hydrogen content in the gas mixture is in the range of 10-70%, then it is possible to use this mixture in local boiler houses or thermal power plants, but the extraction of hydrogen from the gas mixture and further work with pure hydrogen will also be justified. The latter case also applies to the variant of hydrogen content above 70%. Any of these options will inevitably require additional specific technologies and equipment. This applies both to the stage of gas separation and gas purification, as well as storage and transportation of the hydrogen gas mixture and especially pure hydrogen.
A special consideration when considering this point is the question of the possible share of helium and other inert gases in the composition of the gas mixture. The beneficial utilization of these expensive gases should not be overlooked.

- What is the possible volume of natural hydrogen production and what is the forecast for its reserves

Obviously, one well successfully drilled for hydrogen cannot be a subject of industrial interest. We need to discover a deposit. In the usual sense, a hydrogen field can be very different from traditional oil or gas fields. Perhaps this will be a compact area, where it will be enough to place only a few wells. This follows from the fact that the hydrogen concentration can increase greatly with increasing drilling depth. On the other hand, hydrogen release points can be distributed over a relatively large area, which can complicate the development of such a field. In any case, proven hydrogen reserves, along with its concentration, will be the determining indicators for choosing a field development scheme.

- Options for storing and transporting natural hydrogen

First of all, it is necessary to take into account the location of consumers relative to the discovered deposits of natural hydrogen. Of the known options, in this case, cryogenic technology is clearly eliminated, since liquefying hydrogen in the fields, even theoretically, looks very problematic. There are only two real options left. This is a technology for storing and transporting compressed hydrogen or hydrogen in organic carriers (LOHC). Moreover, if the volume of hydrogen extracted from the subsoil is conditionally sufficient, then it may be more expedient to use compression technology (what a conditionally sufficient volume is is a subject of debate). Compressed hydrogen can be transported from production sites either by road, which is very difficult, but feasible, or through a specially constructed pipeline, with the simultaneous solution of all specific technical and administrative problems.


Hydrogen gas transportation concept with truck gas tank trailer. Envato Elements. 47NRVC6TB2

There are examples of operating hydrogen pipelines, but their number is very limited, and the operating conditions are very different from those that will be found in the fields. When the amount of hydrogen produced is relatively small or medium, technology using organic carriers may be more acceptable for storing and transporting it. However, this will require the construction of a hydrogenation unit at the fields, and a dehydrogenation unit at the delivery site. This will require additional costs, but overall the scheme still looks realistic. Transportation can also be carried out by road transport or through product pipelines.

Real geological research and results of searching for natural hydrogen

Among specialized organizations, the English company Getech provides fairly comprehensive information. The company's approach relies on mineral systems analysis to predict the location of natural hydrogen deposits in the subsurface, which behave much like mineral or hydrocarbon deposits. The workflow is based on understanding the genetic factors involved in the development of the natural hydrogen system: classifying them into sources, migration routes, reservoirs, traps and gates in much the same way as the oil industry has successfully done for many decades. Getech's internal databases (including Globe and gravity and magnetic data repositories) provide layers of data and proxies that can form the basis of the analytical process, performed using proprietary machine learning/artificial intelligence workflows and powerful geospatial risk mapping software such as Exploration Analyst.

In describing the geological assessment scheme, the company states: “...once free H₂ gas is released from the source rocks, it needs to migrate into a formation or structure where it can collect. Migration is expected to occur primarily by advection, which occurs primarily along faults and faults. Structural analysis provides the basis for pipeline mapping, but it must also include stress field analysis to understand whether these faults are “open” or “closed.” The secondary migration route, diffuse migration, should also be taken into account. This occurs when free H₂ permeates through porous sedimentary rocks, similar to the diffusive migration of helium and nitrogen. This assessment is complemented by the use of Getech paleogeographic and paleogeological data from Globe to model the parent lithologies that were eroded over geologic time to form these sedimentary units and therefore allow us to estimate the porosity and permeability characteristics of these strata. There may be additional geological factors that allow underground migration of hydrogen in a state of dissolution, i.e. dissolved in groundwater, rather than the free migration of gas associated with advection diffusion.

In addition, the company has extensive geological databases for many countries, which contain:

- Magnetic Products
    Compilation of numerous reprocessed surveys
    Reduction-to-pole and advanced processing
    Depth to basement/sediment thickness from integrated G&M approach constrained by independent data
    Full country or sub-area packages
- Seismic Products
    Scanned and vectorised 2D seismic data
    Delivered in SEG-Y format with navigation files
    Well data also available with various composite logs in LAS format
    Sample data available for review
- Further Insight
Our Regional Reports provide market-leading insight into the geological evolution and potential hydrocarbon prospectivity of specific hydrocarbon basins, under-explored areas and frontier regions

The search for white hydrogen is gaining momentum. Below we provide a map showing the countries in which the presence of white hydrogen is known to varying degrees, as well as their current level of involvement in this process.

Natural hydrogen in the world



We also accompany this map with an extensive list of information sources, including scientific articles, marketing reports, press releases, social media posts and news reports.
Although the activity of white hydrogen followers is growing, the real holiday for everyone will be the day when researchers point to the exact place where hydrogen exists under the surface, and technologists drill a well in this place and get its real flow.

  They went hunting for fossil fuels. What they found could help save the world. / By Laura Paddison, CNN, October 29, 2023
  The industrial exploitation of white hydrogen, myth or reality? / Guillaume, Project Manager in Alcimed’s Energy Environment Mobility team in France / Published on 12 January 2024
  White hydrogen can be a game-changer in Colombia's green transition. Here's why / Ricardo Roa Barragán / CEO, Ecopetrol / Jan 16, 2024
  Prospectors hit the gas in the hunt for ‘white hydrogen’ / Jillian Ambrose / The Guardian, 12 Aug 2023
  A new gold rush? The search for the natural hydrogen motherlode is coming to Canada / Kyle Bakx / CBC News / Jan 26, 2024
  White hydrogen – Switzerland joins the scramble for ‘clean oil’ / LUIGI JORIO / SWI swissinfo.ch / October 30, 2023
  Excitement grows about ‘natural hydrogen’ as huge reserves found in France / By Paul Messad / Euractiv / 30.06.2023
  'Massive spring' of almost-pure natural hydrogen found in Albanian mine, emitting at least 200 tonnes of H2 a year / By Leigh Collins / Hydrogen Insight / 9 February 2024
  Looking for natural hydrogen in Albania and Kosova / Dan Lévy, Molly Boka-Mene, Avni Meshi, Islam Fejza, Thomas Guermont, Benoît Hauville, Nicolas Pelissier / Front. Earth Sci., 17 April 2023 / Sec. Geochemistry / Volume 11 - 2023 | doi.org/10.3389/feart.2023.1167634
  Massive underground reservoir of natural hydrogen in Spain 'could deliver the cheapest H2 in the world' / By Rachel Parkes  / Hydrogen Insight / 6 April 2023
  Natural hydrogen found? | State-owned oil company analysing five sites across South Korea / By Leigh Collins / Hydrogen Insight / 31 March 2023
  Competitive advantage for Swedish industries? Natural Hydrogen discovered in Sweden (in 1988 by Vattenfall) / Natural Hydrogen Ventures / LinkedIn
  White (Natural) Hydrogen Industry Research Report 2024 - Focus on Exploration, Identified Deposits, and Future Scenarios /  Research and Markets, Apr 01, 2024
  ‘Gold’ hydrogen: natural deposits are all over the world – but how useful is it in our energy transition? / by David Waltham / The Institute of Materials, Minerals & Mining (IOM3) / 15 January 2024
  Natural hydrogen could change the world, if we understood it / By David Fickling / Bloomberg / Aug 1, 2023
  South Africa explores ‘white’ hydrogen potential / Sergio Matalucci December / pv magazine / December 19, 2023
  2SITE and Gold Hydrogen have Signed a MoU for the Development of a Natural Hydrogen Pilot Plant on the Yorke   Peninsula, South Australia / BUSINESS WIRE / November 26, 2023
  40 Companies Join Race for Natural Hydrogen Deposits / By Rystad Energy / Mar 13, 2024
   「ホワイト水素」、グリーン超えるか / Nikkei GX / 01.01.2024
  Natural hydrogen exploration and usage being examined by Brazil's national oil company Petrobras / By Polly Martin / Hydrogen Insight / 20 March 2024
  Natural hydrogen emanations in Namibia: Field acquisition and vegetation indexes from multispectral satellite image analysis / Isabelle Moretti, Ugo Geymond, Gabriel Pasquet, Leo Aimar, Alain Rabaute / International Journal of Hydrogen Energy, Volume 47, Issue 84, 5 October 2022, Pages 35588-35607
  Interest in white hydrogen grows / TAGESSPIEGELBACKGROUND,  Energie & Klima Von Linda Osusky
  Hydrogen emissions from hydrothermal fields in Iceland and comparison with the Mid-Atlantic Ridge / Valentine Combaudon, Isabelle Moretti, Barbara I. Kleine, Andri Stefánsson / International Journal of Hydrogen Energy, Volume 47, Issue 18, 28 February 2022, Pages 10217-10227 /
  THE PLACE OF NATURAL HYDROGEN IN THE ENERGY TRANSITION / The earth2 initiative / February 2023
  Migration of Natural Hydrogen from Deep-Seated Sources in the São Francisco Basin, Brazil / Frédéric-Victor Donzé, Laurent Truche, Parisa Shekari Namin, Nicolas Lefeuvre and Elena F. Bazarkina / Geosciences 2020, 10(9), 346; doi.org/10.3390/geosciences10090346
  The occurrence and geoscience of natural hydrogen: A comprehensive review / Viacheslav Zgonnik / Earth-Science Reviews, Volume 203, April 2020, 103140
  Maricá (Brazil), the new natural hydrogen play which changes the paradigm of hydrogen exploration / Alain Prinzhofer, Christophe Rigollet, Nicolas Lefeuvre, Joao Françolin, Paulo Emilio Valadão de Miranda / International Journal of Hydrogen Energy, Volume 62, 10 April 2024, Pages 91-98
  Burning fires at the Mount Chimaera or Yanartas near the village Çıralı at the Mediterranean coast in the province of Antalya / Roland Knauer / Alamy Stock Photo / 7 May 2013
  Diffused flow of molecular hydrogen through the Western Hajar mountains, Northern Oman / Viacheslav Zgonnik, Valérie Beaumont, Nikolay Larin, Daniel Pillot & Eric Deville /  Arabian Journal of Geosciences,  Volume 12, article number 71, (2019) / Published: 21 January 2019
  Natural H2 in Kansas: Deep or shallow origin? / J. Guélard, V. Beaumont, V. Rouchon, F. Guyot, D. Pillot, D. Jézéquel, M. Ader, K. D. Newell, E. Deville / Geochemistry, Geophysics, Geosystems, Volume18, Issue5, Pages 1841-1865    / 03 April 2017 / doi.org/10.1002/2016GC006544
  Natural Molecular Hydrogen Seepage Associated with Surficial, Rounded Depressions on the European Craton in Russia /     Nikolay Larin, Viacheslav Zgonnik, Svetlana Rodina, Eric Deville, Alain Prinzhofer & Vladimir N. Larin / Natural Resources Research / Published: 15 November 2014 / Volume 24, pages 369–383, (2015)
  Discovery of a large accumulation of natural hydrogen in Bourakebougou (Mali) / Alain Prinzhofer, Cheick Sidy Tahara Cissé, Aliou Boubacar Diallo / International Journal of Hydrogen Energy, Volume 43, Issue 42, 18 October 2018, Pages 19315-19326
  Geochemistry of reduced gas related to serpentinization of the Zambales ophiolite, Philippines / T.A. Abrajano, N.C. Sturchio, B.M. Kennedy, G.L. Lyon, K. Muehlenbachs, J.K. Bohlke / Applied Geochemistry, Volume 5, Issues 5–6, September–December 1990, Pages 625-630
  Bridging Natural Hydrogen and Geothermal Energy / Dr Eric C. Gaucher CEO & H2 explorer Lavoisier H2 Geoconsult / 05.10.2023
  Hidden hydrogen. Does Earth hold vast stores of a renewable, carbon-free fuel? /Eric Hand / 16 Feb 2023
  Real-time hydrogen mud logging during the Wenchuan earthquake fault scientific drilling project (WFSD), holes 2 and 3 in SW China / Zhen Fang, Yaowei Liu, Duoxing Yang, Lishuang Guo & Lei Zhang / Geosciences Journal /  Volume 22, pages 453–464, (2018)
  Hydrogen generation from mantle source rocks in Oman / C. Neal, G. Stanger / Earth and Planetary Science Letters, Volume 66, December 1983, Pages 315-320
  The gold hydrogen rush: Does Earth contain near-limitless clean fuel? / By James Dinneen / 31 January 2024

By the Editorial Board