Earth’s Crust May Harbor 'Gold' Hydrogen — Trillions Of Tons Could Power The World For Tens Of Thousands Of Years

In 1987 a worker who lit a cigarette beside a newly drilled water well in the Malian village of Bourakebougou triggered an unexpected explosion. The blast came from previously unrecognized pockets of flammable hydrogen rising from a subsurface reservoir. The well was temporarily sealed, then re-examined in 2011 by Petroma (later renamed Hydroma). By 2012 the company had converted the site to generate electricity for the village, which still relies on that hydrogen today.

Why Bourakebougou Matters

Bourakebougou is the world’s first known productive natural hydrogen well. Unlike manufactured hydrogen, this gas forms in the crust through geologic processes and — when paired with oxygen in fuel cells — can generate electricity with only heat and water as byproducts. That has sparked global interest because hydrogen is a critical industrial feedstock and a potential low-carbon energy carrier for transport, buildings and industry.

How Natural Hydrogen Is Formed

Scientists have long known rocks can produce hydrogen, but they assumed the gas could not accumulate in reservoirs the way oil and gas do because hydrogen is light and reactive. The Mali discovery and subsequent finds have overturned that view. Researchers now recognize that hydrogen can be generated and trapped in the crust when a set of geological conditions coincide.

Key Geological Ingredients

• Water: Groundwater is essential; generation is typically limited to roughly the top 10 miles (≈16 km) of the crust.
• Source Rocks: Iron-rich rocks (e.g., basalt, gabbro) produce hydrogen via hydration reactions; uranium- and thorium-rich rocks (e.g., some granites) produce alpha particles that split water (radiolysis).
• High Temperatures: Source rocks heated to about 250–300 °C (480–570 °F) sustain rapid hydrogen-generating reactions.
• Reservoir Rock: Porous or highly fractured rocks (commonly sandstones) that can store migrating hydrogen.
• Seal: An effective impermeable cap (shale, salt, etc.) present during hydrogen generation to trap the gas.
• Low Microbial Consumption: Minimal microbial activity in the generation/accumulation zone, since microbes consume hydrogen.

How Much Hydrogen Is There?

Estimates vary but are eye-opening. A review led by Chris Ballentine suggests Earth’s continental crust has produced enough hydrogen over the past billion years to meet today’s energy needs for roughly 170,000 years, though much has escaped to the atmosphere. A 2024 estimate by Geoffrey Ellis and colleagues put global crustal hydrogen stocks at about 6.2 trillion tons (≈5.6 trillion metric tons), roughly 26 times the mass of remaining oil. The researchers stress that only a small fraction would need to be recoverable to significantly supplement energy supplies — they estimate extracting about 2% could replace current fossil-fuel use for around 200 years.

Mapping and Early Exploration

In January 2025 Ellis and colleagues published the first prospectivity map for the contiguous United States using gravity and magnetic survey data to infer crustal composition and likely migration pathways. The map scores areas from 0 to 1 for hydrogen prospectivity based on the six geological requirements described above. Exploratory drilling has concentrated in regions such as the Midcontinent Rift (rich in iron-bearing rocks) and in exposed ophiolites in places like Oman.

Stimulated Hydrogen Production

“Stimulated” production — injecting water into hot, reactive rocks to accelerate hydration reactions or radiolysis — is now being piloted. A year ago industry skepticism was common; today attitudes are shifting as field tests and pilot projects increase. Proponents say stimulation could increase hydrogen yields in favorable geology, though technical, environmental and economic questions remain.

Benefits, Limits and Commercial Challenges

Natural hydrogen can offer lower lifecycle carbon emissions than gray hydrogen (which today is mostly produced from steam-methane reforming and emits about 1 billion tons of CO2 per year, roughly 2.4% of global emissions). It also has built-in subsurface storage. Potential uses include powering mines (where drilling already intersects deep rocks), supplying fertilizer production and other industrial feedstocks, and providing low-carbon fuel for transport and power.

However, most estimated hydrogen stores may be too deep, offshore, or too small to develop economically. Transporting hydrogen from remote deposits to demand centers can be costly, and on-site processing infrastructure may be required. Additionally, careful site assessment is needed to ensure seals were present during hydrogen generation and to evaluate microbial consumption, resource size and environmental risks.

Outlook

Experts remain cautiously optimistic. Dozens of exploratory wells worldwide — more than a dozen in the U.S. alone, according to Ellis — have returned encouraging signs of hydrogen. While natural hydrogen is not a silver bullet for the climate crisis, it could become an important low-carbon complement to renewable electricity, green hydrogen production and other decarbonization strategies.

“The potential that's down there is quite, quite large,” said Geoffrey Ellis. “But the key question is how much of it is accessible and economical to produce.”