Hydrogen found underground and generated by natural geochemical processes in the earth – known as geologic, natural, gold or white hydrogen – has become a regular fixture in news headlines.
High-profile findings from France to Albania have prompted some analysts to herald a new “gold rush”, as investors bet big on hoped-for resources.
Some now believe that geologic hydrogen is more abundant than previously thought, and generated in significant quantities when certain iron-rich rocks react with water [1].
Yet despite growing research, it remains an exceedingly early-stage and little-understood topic. Here are the facts key to understanding geologic hydrogen’s clean energy potential.
Geologic hydrogen discoveries currently supply the world with less daily energy than a single wind turbine
Despite recent high-profile findings from France to Albania, the world’s only documented hydrogen producer well is located in the village of Bourakébougou, Mali.
It produces almost pure hydrogen from a shallow reservoir layer at a very low rate of about 5 to 50 tonnes per year. This is equivalent to 0.3 to 3 barrels of oil per day – a power output less than a tenth of a single medium-sized wind turbine [2].
With the exception of Mali, no findings of geologic hydrogen to date have flow tests measuring the rate at which a well can extract hydrogen from underground and thus demonstrating evidence that hydrogen can be produced commercially.
Only the finding in Mali can be firmly considered a “discovery”, while all others are speculative in nature: natural “seeps” where some hydrogen has been detected to leak out from the earth’s subsurface, or “shows” where some traces of hydrogen have been observed during the drilling of a well. Neither of these terms indicate evidence of producible hydrogen.
The most promising geologic hydrogen finds to date lack decarbonisation potential
“Mammoth”, “titanic”, “vast” and “limitless” are just some of the words used to describe recent finds of geologic hydrogen. However, assessing their decarbonisation potential reveals a less promising picture.
A recent finding in Albania is said to have the highest flow of any geologic hydrogen source measured to date. However, the quantity of hydrogen contained in the find remains speculative and cannot yet be classed as a discovered accumulation [3].
At about 200 tonnes of hydrogen a year, the find’s estimated flow is just 1/350th of what a typical steel plant consuming 70,000 tonnes of hydrogen per year would require.
In a best-case scenario, this entire find in Albania is estimated to contain a modest 5,000 to 50,000 tonnes of hydrogen – equalling just 1/2000th of one year’s global hydrogen consumption. This is far too small an amount to justify commercial exploitation, or to support a meaningful energy transition project [4].
Even if abundant, most geologic hydrogen won’t be accessible or easy to recover
Recovering just a few percent of undiscovered geologic hydrogen could satisfy projected global demand for hundreds of years, according to an unpublished study by the US Geological Survey, which estimates up to five trillion tonnes could exist underground.
Those behind the study acknowledge that most of this estimated resource would likely be inaccessible. For any portion that is, recovery would likely remain extremely challenging.
As much as 23 million tonnes of hydrogen – about a fourth of annual global consumption [5] – is already estimated to seep from the earth to the atmosphere each year. Seeps are typically “diffuse”, meaning they are spread over very large areas, making this hydrogen very difficult to capture.
Seeps furthermore lack pressure support, resulting in low flow rates unsuitable for commercial production. Good flow rates can only be achieved from hydrogen trapped at excess pressure in a porous and permeable reservoir: the higher the pressure, the higher the flow rate for production.
For real-world commercial and decarbonisation potential, future hydrogen finds must be made in more favourable geology and pressure settings, where flow rates many times higher than those seen to date can be achieved.
Geologic hydrogen finds often contain very little hydrogen
Geologic hydrogen is often found mixed with other naturally-occurring gases, such as methane, carbon dioxide or nitrogen.
While commercial exploitation of geologic hydrogen would require a large portion, at least 60%, of sampled gas to be hydrogen, hydrogen content is relatively low in many hydrogen finds to date – often under 40%.
Producing pure hydrogen from such a mixed source, provided recovery is possible, would require separation of the hydrogen from other gases. This is technically possible but challenging; it could prove costly and create large amounts of waste products.
A recent high-profile finding in the Lorraine region of France, reported from a coalbed methane test well, sampled a maximum of 20% hydrogen mixed with other gases at a depth of 1,250 metres. This percentage rapidly decreased at shallower depths.
Given that most of the gas in the Lorraine find is methane rather than hydrogen, exploitation would therefore be a coalbed methane development with minor amounts of hydrogen as a byproduct.
Speculation that the concentration of this hydrogen find could rise to 90% at a greater depth is based on pure extrapolation and no physical evidence. Moreover, achieving commercial flow from coals buried deeper than 1,200 metres would be extremely challenging and has not been accomplished anywhere before [6].
Extracting geologic hydrogen, like any other resource, will have environmental impacts
Like all forms of hydrogen, geologic hydrogen will not necessarily be low-emission – despite claims that extracting it will be cleaner than producing hydrogen from both renewable and fossil fuel energy sources.
In one “first estimate” life-cycle assessment of geologic hydrogen production and processing, its greenhouse gas intensity was found to vary considerably based on factors such as gas composition, well productivity, depth, and pressure.
Greenhouse gas intensity was estimated to be very low for a deposit of geologic hydrogen with a high percentage of hydrogen (85%) and a lower percentage of methane, at around 0.4 kilograms of carbon dioxide equivalent per kilogram of hydrogen produced (kg CO2e/kg H2).
However, a lower percentage of hydrogen (75%) mixed with a higher percentage of methane (22.5%) was found to emit 1.5 kg CO2e/kg H2 – a level of emissions 50% higher than the Hydrogen Science Coalition’s clean hydrogen definition.
Emissions or other impacts are likely to stem from energy used to power the extraction process, waste products such as other gases or significant amounts of water, and leakage of hydrogen and other gases along the supply chain.
Production of hydrogen from poor-quality reservoirs or deep-buried coals may require fracking or other forms of well stimulation, bringing about further environmental concerns.
Geologic hydrogen is unlikely to be a renewable resource
Not enough is known about geologic hydrogen occurrences to date to firmly state whether their replenishment, if any, is on a timeline short enough to be considered a “renewable” resource.
It has been reported that pressure has not declined despite years of hydrogen production at the Bourakébougou well in Mali, however, production rates from this well are very small and pressure was low to begin with.
France’s National Centre for Scientific Research, CNRS, which is closely involved in research on the topic, has cautioned that “natural hydrogen is not a renewable resource, in the sense that production rates are far too slow compared to the world’s energy needs”.
Geologic hydrogen won’t be where we need it
Although geologic hydrogen has been found around the world, its location is unlikely to be convenient to where it is needed most.
Hydrogen is more difficult to transport than oil or gas, requiring expensive infrastructure that caters to its technical and safety challenges. It is a difficult-to-contain molecule with high diffusivity, has a much lower energy density, and is intrinsically more dangerous when it comes to fires and explosions.
To date, almost all hydrogen is produced and used at the same site. Transporting hydrogen over long distances via pipeline or ship is highly inefficient, involving uneconomic energy losses and emissions from leakage that could erase any potential climate benefits.
Geologic hydrogen is far too early-stage to create the energy transition impact that we need today
99% of hydrogen in use around the world today is made from fossil fuels and responsible for more emissions than the global aviation industry. Decarbonising this with near-zero emission hydrogen must be a priority, and geologic hydrogen simply won’t be available to do this within the timeframe needed to limit global warming to 1.5 degrees.
This is because it has yet to be proven that geologic hydrogen can be commercially developed at scale, with no suitable finds discovered to date.
Little policy and legislation is also presently in place to regulate exploration activities, and as with other forms of hydrogen, there will be a need for parameters to define and assess what constitutes clean, near-zero emission hydrogen with minimal extraction impacts.
The final take?
Future finds of hydrogen in reservoirs suitable for continuous, commercial-scale collection of the gas would present a very welcome opportunity to decarbonise current-day hydrogen production. At present, the existence of such a resource is purely theoretical.
Finds of geologic hydrogen will need to progress through many steps to reach commercial viability, similar to an oil and gas project, before being classed as a legitimate energy “reserve” [7]. No find of hydrogen to date has moved beyond the first step of this process.
Given growing interest in geologic hydrogen exploration, it is very likely that further shows will be found and that some finds will progress to the status of “discoveries” or “resources”. Some may even reach “reserve” status, with commercial exploitation on a small scale.
However, considering findings to date, what we know about geologic hydrogen systems, and the fact that favourable settings appear rare, the odds of finding geologic hydrogen that can be extracted at the scale of large natural gas developments looks relatively slim.
Footnotes:
[1] Geologic hydrogen is also thought to more rarely be generated by gamma rays, naturally emitting from certain types of rocks, splitting water molecules, or by degassing of the earth’s hydrogen-enriched lower crust and mantle.
[2] The Bourakebougou-1 well in Mali produces 1,500 cubic metres per day of hydrogen from a shallow reservoir layer at a depth of 110 metres, equivalent to 2.9 barrels of oil per day (BOE/d). At such modest well rates, thousands of wells would be needed to match the output of one small gas field, or 10 wells to match the power output of one average-sized onshore wind turbine.
[3] This line was updated to reflect further information provided by the authors of a paper on this find published in the journal Science. Detailed analysis of gases evacuated from mine shafts of this find in Albania show a mixture of hydrogen and other gases. There are no accompanying measurements of gas pressure, which are essential to progress this find to the status of a discovered accumulation. To reach this stage, a dedicated production test with the purpose of proving a connected volume of hydrogen gas and establishing commercial production rates must be carried out.
[4] Based on an estimated deposit of 50,000 tonnes of hydrogen, and the International Energy Agency (IEA)’s most recent estimate that the world consumes 95 million tonnes of hydrogen per year. The deposit thus represents 50,000/95,000,000 = 1/2000th of one year’s global hydrogen production.
[5] Global consumption of hydrogen is currently around 95 million tonnes per year, according to the IEA.
[6] Hydrogen shows reported in Lorraine, France (an old mining district) were reported from a coalbed methane test well (Folschviller-1). Gas composition tests were conducted as part of a European program looking at the viability of coalbed methane development (Regalor project). Based on the reported depths of gas shows quoted and previously published information about the well (EGL press release 2006; Allouti et al, 2023), it is likely these hydrogen shows come from coal beds sandwiched between tight sandstones and shales. Coals can adsorb significant quantities of gas: they preferentially adsorb methane, but can also adsorb hydrogen (Iglaurer et al, 2021).
[7] These steps would include flow-testing to demonstrate the technical feasibility of recovering hydrogen, identifying potential buyers, carrying out an economic viability assessment, issuing a field development plan, obtaining stakeholder and regulatory approvals, performing detailed engineering studies for surface facilities and wells, and firming up final cost estimates and project economics. These steps and more must occur before the project reaches final investment decision, and only at this stage, does the resource mature to the “reserve” class. This refers to firmly discovered resource volumes for which recovery has been demonstrated to be technically feasible, commercially viable and where regulatory approvals and financial commitments are in place to execute the project.
