Researchers have discovered a potential natural hydrogen deposit under the coalfields of the northeastern French Lorraine region – possibly the world’s largest reserve of this gas!

Is a new chapter about to open in the history of the Lorraine mining basin? Until now, this region at the border between France and Germany was best known for its coal mines, the last of which was shut down 20 years ago. But in the future it could become world famous for another major energy source hidden beneath its soil: hydrogen, or more precisely dihydrogen (H₂). This new discovery is the result of analyses conducted by Philippe de Donato and Jacques Pironon, research professors at the GeoRessources Laboratory, in the nearby city of Nancy1. “Our data indicates that the ground under the Lorraine mining basin is very rich in white hydrogen,” de Donato reports. “If confirmed, this discovery could be a big step forward in the transition towards clean, climate-friendly energy sources.” Generally speaking, hydrogen is widely considered an essential driver in the effort to replace fossil fuels like coal, petroleum and natural gas. Unlike the latter, its combustion does not produce carbon dioxide (CO₂), the greenhouse gas (GHG) thought to be the main contributor to climate change. For this reason, there is great hope that hydrogen will be used to power future vehicles equipped with fuel cells (a system that relies on hydrogen and oxygen to produce electricity). It could also provide a clean alternative for all of the industries that are currently dependent on methane, including cement plants, steel production, metallurgy, etc.

The installation for monitoring underground gas levels, capable of taking measurements at depths down to 1,100 metres. White” hydrogen is the term used to designate dihydrogen that forms naturally underground. “It’s called ‘white’ because its production doesn’t generate greenhouse gases,” Pironon explains. “Unlike ‘black’ and ‘grey’ hydrogen, which are manufactured by processing coal and natural gas respectively – in other words, fossil fuels that generate large amounts of GHGs – white hydrogen is directly available.”

White hydrogen is greener than green hydrogen…

As a result, “this gas is even more ecological than ‘green’ hydrogen, which is produced by the electrolysis of water using electricity from renewable energy – solar or wind”, the researcher adds. “Indeed, these two energy sources are not neutral in terms of CO₂emissions, which are released throughout their production chain and during their transport.” “Our discovery came somewhat by chance,” de Donato recounts. At first the geologists were looking for another resource beneath the Lorraine countryside: methane (CH₄) resulting from the thermal evolution of coal over geological time. “Conducted as part of the REGALOR project2, which was launched in 2018 with the independent power company La Française de l’Energie, the purpose of our mission was to confirm an assessment carried out in 2012 by France’s IFPEN petroleum and new energies institute. After analysing a sample of the soil under the Lorraine mining basin, the institute concluded that it harboured 370 billion cubic metres of methane, which represents eight years of gas consumption in France.” Verifying this estimate required the continuous measurement in situ (directly underground at depths of more than 1,000 metres) of the concentration of gases dissolved in the water of the aquifer, the water-permeable subterranean rock layer. To meet this challenge, the researchers had to develop a specialised probe. Created in collaboration with Solexperts, this innovative system, dubbed SysMoG™, was patented in April 2023.

A close-up view from above of the SysMoG™ probe in position before being lowered into the borehole. The monitoring device was miniaturised to fit into a shaft 6 cm in diameter. In late 2022, it made it possible to establish a “profile” of the gas concentrations at various depths in a mine shaft outside the local town of Folschviller. Analyses of coal seams at 600 and 800 metres revealed a first important finding: the gas mixture present at those levels is more than 96% methane, i.e. nearly pure! Related: HyTerra Undertakes A$1 Million Raise for Advancing Natural Hydrogen Ventures in Mid-West USA Confirming the IFPEN’s initial estimates, “this data is extremely encouraging”, de Donato says, “because it shows that the underground methane is not contaminated by an unwanted toxic or corrosive gas, as was the case with the Lacq deposit (the country’s largest natural gas field, in southwestern France – Editor’s note). So there will be no need for purifying treatments, a fact that greatly reduces its carbon footprint”. Even more intriguingly, while conducting their measurements the researchers also detected the presence of another gas: the above-mentioned white hydrogen. “At 200 metres the concentration of this compound was very low – around 0.1%, which is quite common at this depth,” de Donato says. “So this initial measurement came as no surprise.” But then, as the probe descended further into the shaft, hydrogen levels began to rise… “We really started to wonder what was happening when they jumped from 1% to 6% between 600 and 800 metres. It was the first time anywhere in the world that such a high concentration of hydrogen had been found underground.” And that was only just the beginning. At 1,100 metres the level exceeded 15%. “That’s when we realised that we had possibly found an unsuspected deposit of white hydrogen!” de Donato exclaims. The researchers believe that the precious gas is produced continuously by a veritable hydrogen “factory” hidden beneath our feet, and whose raw materials are water molecules and minerals made up of iron carbonates (FeCO₃and Ca(Fe,Mg,Mn)(CO₃)₂). As Pironon explains, “The earth around the Folschviller mine is rich in those two types of compounds. When they come into contact, a physicochemical reaction called redox occurs, in which the minerals separate water molecules (H₂O) into oxygen (O₂) and hydrogen (H₂).”

Bright prospects

According to the geologists, the hydrogen detected at 1,100 metres is produced at greater depths and rises by diffusion – a hypothesis that suggests the presence of even larger concentrations further down! “According to initial simulations, at 3,000 metres levels could exceed 90%,” de Donato reports. If these figures are correct, the Lorraine reserve could contain approximately 46 million tons of natural hydrogen, the equivalent of more than half of the world’s current annual production of grey hydrogen! However, these conjectures have yet to be confirmed. “In the coming weeks, we will measure the levels at depths of 800-1,000 metres in three other shafts located within a 40-kilometre radius of the one that we’ve already studied, to verify that the gas is present throughout the entire perimeter,” de Donato explains. “Then we’ll have to validate our estimates of the hydrogen concentration at 3,000 metres – with the help of industry players in order to drill that deep.” Lastly, viable techniques for extracting the hydrogen will need to be developed, and are already mobilising researchers… In the meantime, La Française de l’Energie has applied for a natural hydrogen exploration and production permit, “starting in March 2023”, according to Romain Chenillot, the company’s geoscience–mine gas director. It must be admitted that this discovery holds great promise. In addition to being “clean”, the hydrogen from the Lorraine offers another significant advantage: “It could supply the pipeline of the ‘mosaHYc’ 3 project, a programme aimed at building a European hydrogen transport network to link the Saar (Germany), Eastern France and the Luxembourg border area as of 2026,” Pironon points out. Will this make France a future El Dorado for natural hydrogen? https://www.youtube.com/watch?v=a1S-dy8ykDA

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