The Potential for Geologic Hydrogen for Next-Generation Energy
not unlike that of—you guessed it—olives.) This interaction can cause the water to be reduced to oxygen, which bonds with the iron in the minerals, and hydrogen, which then escapes into the surrounding rock.
Once hydrogen has formed, a variety of natural processes can consume the gas. In particular, many microbes survive on hydrogen, and microbiologists have now described a vast, deep biosphere fueled by hydrogen. Additionally, the process by which petroleum forms from organic-rich rocks consumes any available hydrogen. This is one of the reasons why hydrogen is rarely found with hydrocarbon gases like methane or propane.
Any hydrogen that isn’t consumed by these processes may reach porous rocks, where it could form a gas accumulation. But in order for the accumulation to persist, an effective seal rock must be present to hold the gas in place. For decades, geoscientists have assumed that seal rocks could not effectively contain hydrogen accumulations, because hydrogen’s small size would allow it to escape through even the tightest rocks. However, studies show that the diameter of a molecule of two hydrogen atoms is about equal to that of a single helium atom and that the two gases are likely to get trapped by similar rock layers. There are known helium accumulations that have been preserved for as long as 100 million years, so it is reasonable to assume that hydrogen could be trapped for similar time spans.
USGS scientists are incorporating all these factors into their model, which will improve our understanding of the resource potential of natural hydrogen on Earth.
Mapping It Out
As the principal scientist in the USGS effort to evaluate the potential for geologic hydrogen resources, Ellis is leading the USGS effort to map the regions of the conterminous U.S. most likely to contain geologic hydrogen. His team is using the hydrogen system model as the basis of this work. By mapping the distribution of each of the components of the hydrogen system and assessing how well they align they can provide an initial estimate of the potential for geologic hydrogen across the nation.
There are at least two major areas of the country that have favorable geology for the generation of significant volumes of hydrogen. These lie along the Atlantic coastal plain and in the central U.S., underlying parts of the Great Plains and the Upper Midwest.
The Atlantic area of interest stretches along most of the East Coast and is associated with a