There is a whole set of little-known economic activity built around the use of hydrogen. The top uses of hydrogen consumed in the U.S. are for refining petroleum, treating metals, producing fertilizer and processing foods. It is also used by refineries to lower the sulfur content of fuels while biofuel producers use hydrogen to produce hydrotreated vegetable oil (HVO) for use as a form of renewable diesel energy. Interestingly, hydrogen has the highest energy density by weight of any element, which makes it useful as rocket fuel as well. Even though hydrogen is the most abundant element in the universe, it is not readily available in a pure form, often combined with carbon in petroleum reserves and ultimately used to produce a variety of petroleum and plastic products.

By far, the most common technique to obtain hydrogen for these uses is through a process called steam-methane reforming. In this process, high temperature steam (1,300˚ F to 1,800˚ F) is combined with methane, CH₄ (the major component of natural gas), plus a catalyst to produce hydrogen. This process creates the unwanted byproducts of carbon monoxide (CO) and a smaller amount of carbon dioxide (CO₂). Because this process results in some methane release during extraction, requires a lot of energy to produce high temperature steam and produces the unwanted byproducts of CO and CO₂, it is considered an undesirable or “dirty” process. Hydrogen produced in this way is referred to as “gray” hydrogen. The term gray refers to the production process, as the actual hydrogen produced is colorless and odorless and indistinguishable from hydrogen from any other process.

Figure 1. A rock sample with embedded olivine. Source: Public domain

However, with the thought that hydrogen is a naturally abundant element, it’s not a stretch to postulate that it must exist in its pure form in certain places in the Earth. These would be clean pockets of pure hydrogen that could be extracted using conventional well drilling techniques. Without the need for all of the high temperature processing steps, this clean, pure hydrogen source is referred to as “white hydrogen.” Based on this premise the U.S. Geological Survey (USGS) has undertaken a study to define the extent and availability of white hydrogen sources, specifically in the U.S.

Natural hydrogen

The USGS report validates that geologic hydrogen is readily produced by the Earth under a variety of conditions. Furthermore, there is the potential to use the same knowledge gained through oil and gas exploration and extraction techniques to harvest these pockets of hydrogen. Two ready examples are in New Caledonia in the South Pacific and Mali, in West Africa. In New Caledonia, in Prony Bay, underwater vents release warm (109˚ F), alkaline (pH>11) waters rich in hydrogen (between 12% and 34%). In Mali, a vent at the surface produces 98% pure hydrogen, which is burned directly inside a turbine to generate electricity for a nearby village. Clearly there is more to learn and the USGS has developed a strategy that mimics, in many ways, the evolution of the oil and gas industry.

Of course, the first step is to understand the mechanisms that create stores of hydrogen that are economic to recover. As hydrogen is created, it would naturally flow upward and congregate in formations or caverns that consist of non-permeable cap rock. Earth movements could cause these to change with time, so the shapes and composition of these underground “containers” must take that into account. This is analogous to the formation of petroleum deposits, but with a critical difference. Petroleum deposits form, coalesce and accumulate over tens to hundreds of millions of years. The chemical processes that release free hydrogen from their mother rock deposits occur in the range of tens of years, perhaps a generation or so. One example is when groundwater interacts with certain iron-rich minerals, like olivine. The process of oxidizing the mineral under the right conditions separates the oxygen from the water and locks it up, freeing up the remaining hydrogen. This is a fairly quick process that occurs near the Earth’s surface, which makes it a potentially viable candidate for generating a ready supply of white hydrogen for current uses. As we develop a better understanding of this iron rich oxidation process, we may be able to improve the process of hydrogen generation.

As simple as this all sounds there are challenges that must be addressed. In gaseous form, hydrogen at low pressure is not very dense. In small commercial volumes, it needs to be compressed to 3,000 psi to 7,000 psi and loaded on a truck for transport to be economical. This is limited to distances up to about 200 miles. For longer transport via roadway, it is better to cool the hydrogen to a liquid state at -253˚ C. Liquid is denser, though cooling hydrogen to a liquid state has a penalty of about 30% of the energy that is being carried, just to bring the temperature down this low. The preferred method for long distance is to use pipelines, with compression stations close to the point of use. These are the existing solutions that are available today, but they do make hydrogen more complex to handle. Most of these issues would be mitigated as infrastructure is built and as larger volumes of white hydrogen are produced.

Growing the hydrogen economy

One of the obstacles to discovering these types of white hydrogen generators is that our understanding of the hydrogen generating process is limited. In addition, the techniques for hydrogen detection are not fully developed. Though we can rely on petroleum extraction knowledge to some degree, it is not an exact copy of subsurface hydrogen. Once we understand the range of production mechanisms and how to detect them, we can make much better-informed decisions about how to best take advantage of these natural sources. We have a gap in our knowledge — a gap that will be quickly filled. Using rather conservative models of production, a USGS report released in April of 2023 estimates that there may be enough white hydrogen to serve the energy needs of the world for hundreds, maybe even thousands, of years, mimicking the petroleum economy growth after its first discovery.

The possibility of a rapidly expanding access to white hydrogen has stoked interest around the globe. For one thing, on the basis of mass, hydrogen has almost three times the energy of gasoline. When hydrogen burns (combines with oxygen) the only byproduct is water vapor — no carbon emissions to worry about. Hydrogen can be used to produce highly efficient (up to 80% or more) fuel cells that directly convert hydrogen into water and produce a usable electrical current similar to a battery output. Given these attributes, hydrogen could become a viable replacement for batteries in electric vehicless with fuel cells. With high energy density, the possibilities to make non-polluting electric airplanes and ships may become reality. And importantly, unlike petroleum sources, hydrogen is being continuously produced.

Moving ahead

By examining the structure of the Earth, USGS researchers have so far identified two locations in the U.S. that are promising sources of olivine-generated hydrogen: one in the Northeast and another in the Midwest. The midwestern zone underlies Lake Superior and at one time was an active rift zone splitting the continent along a North-South axis. This movement brought large quantities of minerals up toward the surface. The Northeastern area extends along the East coast and was formed during the creation of the Atlantic Basin. This area has been confirmed to be generating hydrogen; however, a definitive capturing structure has not been identified. All of this information is being used to develop strategies to search for and develop naturally occurring hydrogen.

Summary

There is still much research to be done in this field, but around the world acceptance of hydrogen as a viable energy source is gaining traction and resources. Hyundai Nexo and Toyota Mirai cars using hydrogen fuel cells have been on the market since 2020. Others will follow. Hydrogen could be used for direct heating applications as a replacement for natural gas. Existing natural gas pipeline infrastructure is already in place and could be converted for hydrogen transport. The European Union has made hydrogen a key element of their clean energy policy expecting it to cover 20% of its energy needs by 2050. Hydrogen fuel cells are standard equipment on manned space vehicles to turn stored hydrogen and oxygen into water and electricity. In short, the hydrogen genie is out of the bottle and, combined with other “green” technologies will soon be another significant option to reduce anthropomorphic climate change, perhaps as soon as the next generation.

About the author

Scott Orlosky has an MS in Manufacturing and Control Theory from the University of California at Berkeley and has worked over 30 years designing, developing, marketing and selling sensors and actuators for industrial and commercial industries. He has written numerous articles and application notes for speed and position sensors used in industrial and hazardous area environments including an author credit in “Encoders for Dummies.” Scott authored an industrial newsletter for nearly 15 years and is also co-inventor on a number of patents involving design and manufacturing of inertial sensors.