Geologic Hydrogen
What is geologic hydrogen?
Geologic hydrogen is clean fuel that forms naturally underground. This guide explains how it works in plain terms, how it differs from other kinds of hydrogen, and what still has to be proven.
The reaction
How does hydrogen form underground?
Ultramafic rock formations are dense rocks high in iron formed long ago from ancient sea floor. At elevated subsurface temperatures and in the presence of water, the iron phase captures the oxygen while releasing hydrogen into the geothermal fluids that we aim to produce to surface.
Reaching the hot rocks and lifting the hydrogen back to the surface relies on well-established geothermal drilling methods.
Read how we put this into practice in our phased exploration approach.
The climate case
Why is geologic hydrogen called low-carbon?
When hydrogen is used for energy, its only by-product is water. The carbon intensity depends on how the hydrogen was produced. Most hydrogen today is made from fossil fuels or by using large amounts of electricity, and both can carry a heavy carbon footprint.
Geologic hydrogen is different because the earth has already done the work. There is no factory to build and no fuel to burn to manufacture it, so producing it can be far less carbon-intensive. That combination of a clean fuel and a clean source is what makes the resource potential so compelling.
How it compares
How is it different from green, blue, and gray hydrogen?
Gray hydrogen is made from fossil fuels without capturing the carbon, which makes it too polluting for a low-carbon grid. Blue hydrogen adds carbon capture to a fossil-gas process, but requires long-term storage of that captured carbon, known as sequestration. Green hydrogen is made by splitting water with renewable electricity. It is clean, yet it has struggled to deliver at the scale or competitive cost the grid needs.
Geologic hydrogen is the one pathway that could combine scalability, affordability, and low emissions at the same time, because the resource already exists underground. Early estimates place its cost near $1.75 per kilogram, roughly the energy equivalent of a gallon of gasoline at the same price.
Fossil-based, carbon-intensive.
Fossil-based, with carbon capture.
Renewable electrolysis. Cleanest, costliest today.
Our early cost estimate.
Momentum
Is geologic hydrogen real? What has changed recently?
Interest in geologic hydrogen has grown quickly, and so has the credibility behind it. National laboratories, the United States Geological Survey, and university researchers at institutions such as Stanford are actively studying how and where it forms.
States and regulators are paying attention as well. Several states have moved to open their ground to exploration, and federal agencies are reviewing how to permit it. Major investors, including Breakthrough Energy, have backed companies in the field.
The momentum is global. Hydrogen demand is projected to roughly double by 2050, and the ultramafic rock that generates geologic hydrogen exists on every continent, with active work underway in Oman, Australia, Brazil, France, and other parts of the United States. By early estimates, a single prospect could supply close to one percent of US hydrogen demand.
That said, the science is still young, and that is exactly why careful exploration matters.
A realistic view
What still has to be proven?
Exploration carries real uncertainty. Finding favorable geology is not the same as confirming how much hydrogen a system holds, how fast it generates, or how economically it can be produced. Those answers come only from data and drilling.
Fremantle Lake is an early-stage project, and we frame our figures as estimates that guide the work rather than promises about the outcome. You can see how we reduce that uncertainty in our exploration approach and learn about the Fremantle Lake project.
Safety
Is geologic hydrogen safe?
Hydrogen has been used in industrial applications for decades, and its properties are well understood. California also has extensive experience regulating geothermal exploration and drilling, providing an established framework for permitting, environmental review, and well oversight. While geologic hydrogen exploration is an emerging industry, geothermal exploration and well construction use established regulatory and engineering practices.
Fremantle Lake follows applicable regulatory requirements and industry safety practices throughout its exploration activities.
Go further
Have a question we did not cover?
If you are an investor, researcher, or policymaker who wants to understand the science in more depth, we are happy to talk.