For a simple molecule always consisting of just two atoms, hydrogen is labelled with far too many colours, depending on how it’s produced – grey, blue, green the most familiar, then pink, turquoise and orange.
Now another colour is on the palette: white, or gold. And people are searching for it in the most unlikely places, from Mali to France, South Australia and Nebraska.
Hydrogen is emerging as a crucial zero-carbon fuel, that could be used in heavy industry, ships, planes and long-duration energy storage. But hydrogen does not occur chemically uncombined on Earth – it is bound up in water, oil, gas or living matter. So it has to be manufactured, from breaking down hydrocarbons (grey or blue hydrogen) or splitting water using electricity (green, from renewables, or pink, from nuclear power).
Or so it was thought. When I suggested in my basic training course at Shell in the late 1990s that hydrogen might be a constituent of underground gases, the instructor witheringly dismissed it. Most geoscientists assumed that hydrogen, the smallest and lightest element, would escape from the ground immediately, be eaten by microbes, or react with carbon dioxide.
But now it appears that hydrogen is produced naturally within the Earth in large amounts and can be trapped in the subsurface. It was missed because oil companies were not looking for it, and their instruments would not detect it.
The insight came from the village of Bourakebougou in Mali, about 70km north-west of the capital Bamako. A well drilled for water in 1987 instead yielded a flammable gas. Only in 2012 was the gas analysed and discovered to be nearly pure hydrogen. Now it runs a generator to provide electricity.
In the past few years, geologists have combed old records to see where else in the world hydrogen has been overlooked.
Here are some key questions to consider: does natural hydrogen accumulate in quantities that could be found and extracted commercially on a large scale? If so, where and how do we find it? And if it is being formed or released continuously, could it effectively be a renewable energy source, as opposed to non-renewable oil, gas and coal?
There are several ways hydrogen could be formed within the Earth, including reactions of water with iron-containing minerals at high temperatures to make the mineral serpentine, the process of “serpentinisation”, which seems the most favoured theory. Radiation from naturally occurring elements such as uranium or thorium may split water. Or, primordial hydrogen may seep from the deep interior core or mantle, where it was trapped in the planet’s fiery birth.
Areas of ancient iron-rich rocks in contact with water are most promising. Ophiolites – slices of sea-floor forced up during collisions of tectonic plates – convert to serpentine when they react with water, and occur in the Spanish Pyrenees, Oman and New Caledonia.
Natural seeps of burning hydrogen from an ophiolite in Yanartas, southern Turkey, thought to be the ancient Mount Chimaera, may be the origin of the fire-breathing Chimaera monster of Greek legend.
And hydrogen is formed at mid-ocean ridges, where fresh volcanic rocks meet seawater, including Iceland where the Mid-Atlantic Ridge emerges above the waves. These prospective areas don’t coincide with traditional oil and gas basins.
Koloma, which has raised money from billionaire philanthropist Bill Gates, among others, is looking in the US Midwest. Other companies are drilling in Nebraska and Kansas, along the Midcontinent Rift, an ancient geological structure which almost ripped North America apart about 1.1 billion years ago.
Koloma’s chief technology officer, Tom Darrah, told Forbes earlier this month: “It’s on every continent. The scale of how much there is, is profound.”
The US Geological Survey estimates there could be enough natural hydrogen to meet demand for centuries.
Green or blue hydrogen might eventually be produced for $1 to $1.50 per kilogram. But the experience in Mali and exploration in Spain suggests natural hydrogen could be extracted from the ground for 50 to 70 cents per kilogram. That is equivalent to $4 to $5.60 per million British thermal units of natural gas, which is mostly composed of carbon-containing methane, and currently sells internationally for about $11.
Companies are also interested because hydrogen may be found alongside valuable helium, crucial in technologies such as semiconductors, rockets, MRI machines and deep scuba-diving, and whose price is rising as existing sources deplete.
Past drilling in Brazil and Russia has accidentally found concentrations of hydrogen. Explorers are also combing South Australia and Spain. In May, Francaise de l’Energie, a French multi-energy corporation, announced it had found important amounts of natural hydrogen in the coal-mining basin of Lorraine in eastern France.
The leading oil and gas companies have not stepped in, though large French utility Engie has shown interest. Given their past failures on shale, the majors are unlikely to be the successful innovators in new resources.
Instead, small specialist explorers are leading – and investors should beware of speculative claims. These various ventures still have to demonstrate commercial amounts and flow rates through wells.
Hydrogen is less compressible than methane, and has only a third of its energy content by volume, so the fields found so far would be small compared to those of natural gas.
The geological settings that form hydrogen do not contain many highly porous and permeable rocks that would make good reservoirs. Hydraulic fracturing might be required, increasing costs and probably annoying environmentalists (although they might give a zero-carbon fuel special treatment).
Still, even small finds could be useful. Hydrogen is hard to transport, so finding it close to consumers would be valuable. Low-cost natural hydrogen could help the industry scale up much more rapidly, even if accessible volumes are not enough to meet demand on their own.
With growing awareness and attention, the next few years will determine whether natural hydrogen is a geological curiosity, a local resource, or a major contributor to future zero-carbon energy – and whether our palette really needs a new colour.
Robin M. Mills is chief executive of Qamar Energy and author of ‘The Myth of the Oil Crisis’