It is the most abundant element in the universe but needs to be freed from chemical bonds before it can become a fuel. However, in some locations, hydrogen bubbles up naturally.
Energy Blog: Hydrogen Straight from the Earth
Feb 16, 2021
by Michael E. Webber
Indeed, in 2018 more than 70 million tons of hydrogen were consumed for all purposes, mostly to make ammonia for fertilizers and to lighten and sweeten crude oil at refineries. Demand for hydrogen is expected to grow eightfold by 2050, again as a feedstock, but also for transportation, building heat, and power generation.
Unfortunately, there has always been a problem. Though hydrogen is the most abundant molecule in the universe, it typically is not available in free form. It is almost always bound up in water molecules or hydrocarbons. Right now, industry either adds heat to water and methane (a process called steam reforming) or adds electricity to water (in electrolysis) to unbind the hydrogen to make pure H2.
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Both methods work but are energy intensive and expensive. And if the emissions from the energy source or process are not captured, it contributes to global warming.
There is another pathway for producing hydrogen. The iron oxide redox cycle brings water and heat into contact with iron ions to produce hydrogen from a two-step sequence of reduction and oxidation. When ferrous iron (Fe2+) makes contact with water, it oxidizes to ferric Fe3+ and releases H2. The reaction is fast and efficient at high temperatures—around 300 °C—but it is possible at lower temperatures. The pathway also works with other metals, such as magnesium.
While steam reforming and electrolysis must be produced artificially, interestingly enough there are places where iron in the Earth’s crust naturally comes into contact with both heat and water. One such place is the mid-Atlantic ridge. While harvesting hydrogen bubbling up from the seabed is inconvenient, the mid-oceanic ridge outcrops in Iceland. Some of that island’s famous geothermal wells bring hydrogen to the surface along with the hot water Icelanders use for power generation and home heating.
There are other geological sources of hydrogen gas easier to access than mid-ocean ridges. Precambrian cratons—half-billion-year-old blocks of crust in places such as Brazil, Canada, Namibia and Australia—sometimes feature slight, roughly circular depressions where the vegetation dies due to leaking hydrogen gas from the subsurface. In European Russia, according to researchers, there are such rings, called fairy circles, ranging in diameter from 100 meters to several kilometers. Sensors around these circles show reliable flow of H2 from below ground that can be captured and harnessed for fuel.
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Overall, our latest data and understanding suggest that natural hydrogen is available at globally relevant volumes with potentially easier and cheaper accessibility and lower emissions than reforming or electrolysis. This is a new field, though, so we should not pretend to have a perfect understanding of the system, but if it is found to be viable, it could develop rapidly. For instance, by leveraging existing know-how from the oil and gas industry, extraction of hydrocarbons from shale formations went from essentially zero in 2008 to around $150 billion by 2019 and reinvented energy geopolitics along the way.
Natural hydrogen reminds me of the early days of shale in that it’s mostly an idea waiting on better technologies, policies, and market conditions for it to prosper. If it does, perhaps the oil and gas industry can turn its capabilities to extracting hydrogen produced by subsurface geological processes, shepherding in a new era of low-carbon fuels. That way it can avoid job disruption while using its global-scale competencies to ramp-up hydrogen quickly. It could give the hydrogen story the happy ending it deserves.
Michael E. Webber is the Josey Centennial Professor of Energy Resources at the University of Texas in Austin and Chief Science and Technology Officer at ENGIE, a global energy company headquartered in Paris. His book, Power Trip: The Story of Energy, was published by Basic Books.