The US Department of Energy (DOE) has announced it will offer $20m in funding towards technologies to measure and produce naturally occurring hydrogen.
Hydrogen can theoretically be produced naturally through a number of different geological processes (see factbox below), but it has so far only been found in large quantities and purity at one small site in the African country of Mali, where it is burned to produce electricity for local villagers.
However, several companies are hoping to find large stores of natural hydrogen underground, and extracting it from the earth would be far cheaper than producing it via electrolysis or methane reformation.
The DOE will offer financial support for equipment and methods to find, monitor, model and extract H2 from geologic stores of the gas underground via its Advanced Research Projects Agency — Energy (ARPA-E).
It will also fund routes to extract H2 from hydrogen-rich iron minerals found in the Earth’s crust, which can already naturally break down to produce the molecule.
“While the supply of naturally accumulating hydrogen, in and of itself, can enhance the US energy economy, reduced iron minerals within the Earth’s crust have the theoretical potential to produce even more hydrogen from reactions within the subsurface,” ARPA-E explained in a press release.
“Using stimulated mineralogical processes could yield larger quantities of hydrogen than what are produced naturally. Thus, engineering the production of subsurface hydrogen could be a substantial source of clean energy.”
The deadline for full applications for funding is 24 October.
“ARPA-E supports transformational, impactful energy technologies. So, when it comes to geologic hydrogen, we’re asking ‘are there disruptive ways to access this hydrogen source and explore the potential?’” said the agency’s director Evelyn Wang.
“There is significant opportunity to accelerate the development of hydrogen production, and I look forward to the teams pursuing this exploration.”
Natural hydrogen, also known as “white” or “gold” H2, is gaining traction as a way to produce large quantities of the molecule at potentially extremely low cost and lifecycle greenhouse gas emissions.
Analysis of so-called “fairy circles” — depressions on the Earth’s surface with little vegetation associated with seepage of H2 — indicates that these sites alone produce 23 million tonnes a year, not accounting for additional underground reservoirs of hydrogen.
And given the high amount of hydrogen seeping from fairy circles and the constant pressure from the drilling site in Mali, researchers suggest that these stores of hydrogen may be being actively replenished, rather than a static resource that will be depleted over time.
Companies such as Hyterra and Natural Hydrogen Energy are already drilling for H2 in Nebraska and Kansas, while in July, Denver-based start-up Koloma raised $91m in funds, including from billionaire Bill Gates-founded Breakthrough Energy, to tap into these resources.
Outside the US, South Australia has seen a recent boom in start-ups prospecting sites around Kangaroo Island and the Yorke and Eyre peninsulas, which have historically seen high quantities of hydrogen gas when drilling for oil.
And in France, four companies have applied for exploration permits for natural H2 since mining regulations were expanded last year to include this molecule.
There are six known ways in which hydrogen is produced naturally:
In which the mineral olivine located in mid-ocean ridges or ophiolites (a geological formation where sections of the Earth’s mantle rise above sea level) is weathered to form hydrogen-rich fluids. This has been seen in the Semail ophiolite, in the Hajar Mountains of Oman
Radiolysis of water
Radioactive elements in the Earth’s crust — for example in crystalline basement rocks with high content of uranium, thorium or potassium — decompose water molecules trapped in causing a hydrogen pocket, as happened in South Australia
In which “primary” hydrogen (a single hydrogen atom attached to a single carbon atom) escapes from deep within the Earth’s crust. This has been seen in Nebraska, in the US
Iron reduction and sulphur oxidation
Ferric iron in a black smoker (a subsea hydrothermal vent formed from iron sulphide deposits) is reduced to ferrous iron and hydrogen sulphides
Thermal decomposition of organic matter
In which ammonium compounds located in deep sendiments decompose under high temperatures to form hydrogen and nitrogen, for example in hydrogen-nitrogen gas seeps in Oman
Hydrogen is produced by microbes living in the Earth’s crusts, usually co-existing with hydrogen-consuming microbes and found via sediment or aquifers. This has been observed in the coal beds of the Powder River Basin in Montana, US.