How a cigarette sparked a slow-burn search for buried ‘gold’ hydrogen

A lit cigarette provided the first clue to the energy source deep underground. Drillers accidentally set fire to the gas coming out of what they had thought was a dry water well in Bourakébougou, south-west Mali, in 1987. 

Rather than natural gas, whose main component is methane — a driver of global warming — the drillers had struck hydrogen. Now, decades later, the village, population 1,500, is still using this reservoir of the clean-burning gas to generate electricity.

Mali is, so far, the only place in the world to have exploited underground hydrogen deposits. But it may soon be joined by others. The push to ditch fossil fuels means engineers, geologists and prospectors are scouring the globe to see if they can find and extract the gas — also referred to as geologic, gold, or white hydrogen — at scale.

Forty companies, in countries including Australia, Albania, Canada and South Korea, were searching for hydrogen deposits as of the end of 2023, according to consultancy Rystad Energy. That is up from 10 just three years ago.

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“The world needs dependable, affordable energy,” explains Neil McDonald, managing director of Australia-listed Gold Hydrogen, which is drilling prospects in South Australia first discovered and ignored by oil prospectors a century ago. “We are hoping to be a big part of that.”

Such is the need that the International Energy Agency predicts a more than fourfold increase in annual demand for hydrogen: it will have to rise from 95mn tonnes in 2022 to 430mn tonnes in 2050, if net zero emission targets are to be met by replacing the fossil fuels currently used by refineries, power stations and vehicles.   

Most hydrogen in use today is produced by splitting it from natural gas — a process that leaves carbon dioxide as a byproduct. And efforts to produce cleaner versions to meet net zero goals have so far focused on either capturing and storing those carbon emissions, or on using renewable energy to power industrial scale electrolysers to split hydrogen from water.

Drilling for exploitable reserves of naturally occurring hydrogen has not, generally, been considered feasible. “We’ve known about the natural occurrence of hydrogen for over a century,” says Geoffrey Ellis, research geologist at the US Geological Survey. “But it had been assumed that you just couldn’t get accumulations of it.” 

That assumption is now being seriously tested, thanks to discoveries and drilling results in Mali and elsewhere, and as the growing potential market for hydrogen drives efforts to better understand what lies underground.

Last year, scientists looking for natural gas in Lorraine, north-eastern France, hit on what they say could be the largest white hydrogen deposit found so far.  

It’s possible there could be large amounts of primordial hydrogen leaking out of the interior of the Earth

Ellis and his team have modelled worldwide reserves of geological hydrogen, producing a median estimate of about 5tn tonnes. But, given a wide range of uncertainties, the actual amount could be some orders of magnitude higher or lower.

A lot of the gas is created by natural processes, such as the reaction between iron-rich rocks and water at high temperature. But some hydrogen may have become trapped during the formation of the Earth. “It’s possible there could be large amounts of primordial hydrogen leaking out of the interior of the Earth,” says Ellis. 

How much of it can be extracted is not fully understood. However, just 2 per cent of his median estimate would meet the IEA’s demand estimate for a couple of hundred years, Ellis notes. In theory, tapping underground reserves of hydrogen could also be far cheaper than splitting it from natural gas, or from water.

“To make hydrogen through electrolysis in Australia costs a minimum of $6 per kilogramme before transportation,” point out McDonald, at Gold Hydrogen. “Based on Mali’s experience, and our drilling, we strongly believe that we can produce it before transportation for a dollar per kilogramme or less.” 

These lower costs could make naturally occurring hydrogen a “major disrupter,” reckons Molly Iliffe, head of hydrogen at London-based consultancy Baringa. They would potentially accelerate wider use of the gas as a power source, but could also pose a competitive threat to projects extracting hydrogen from water. “People are aware of it but, at the moment, it’s at a very nascent stage,” she says. 

So far, no one is extracting naturally occurring hydrogen at a commercial scale, and the majority of those searching for it are start-ups, which face many uncertainties — ranging from the size, location and purity of deposits to the ease of extraction, potential by-products, leakage rates, and transportation. 

The economics of exploration projects could be helped by the fact that white or gold hydrogen is sometimes found alongside helium — already a valuable gas in industries ranging from defence to medicine.

However, carbon dioxide is often also present, which would need to be captured to prevent harmful emissions. Hydrogen leakage during extraction is another potential problem, too, as the gas can have a knock-on effect on the lifetime of methane — to the extent that hydrogen is considered an indirect greenhouse gas. Allowing it to leak out would therefore lessen its contribution to tackling global warming. 

“The Mali well has drawn a lot of interest and some discoveries in Australia also contribute to momentum building,” observes Paul Harraka, chief business officer at Koloma, a US-based start-up backed by the Bill Gates-founded Breakthrough Energy Ventures, which is exploring for hydrogen. “But it is still very early days. A lot of work still has to happen before geologic hydrogen is deployable at scale.”

And a lot of questions still have to be answered. “What does the infrastructure look like?” Harraka asks. “How long will it take people to find a large reserve — and be able to actually produce it?”