“The game of the moment is to find where it has been released, accumulated and preserved,” says Chris Ballentine, professor and chair of Geochemistry at Oxford University. His insight reveals the race to develop a clean energy source to meet the needs of the future – seeking massive deposits of hydrogen filled naturally in the earth’s crust to provide power to humankind for many generations to come.
Studies conducted more recently have found that the Earth’s crust has produced sufficient hydrogen to satisfy global demand for the past billion years for, roughly, the past 170,000 years. While it does exist, it becomes difficult to locate it in sufficient quantities for economic extraction. Ballentine et al. finally provide an exact ‘ingredient list’ for conditions conducive to hydrogen accumulation – this can assist exploration firms in locating lucrative targets.
There are several documented geochemical processes for the natural production of hydrogen. Perhaps one of the most abundant processes is serpentinization, where water reacts with iron-rich minerals, like olivine in ultra-mafic rocks, to split water molecules, forming hydrogen gas. Another process is radiolysis, whereby radiation from uranium and thorium-rich rocks results in the splitting of water molecules. While serpentinization is associated with ancient oceanic rocks, known as ophiolites, that rifted onto the continents, radiolysis occurs in large igneous bodies, like basalts, and Archaean greenstones. For microbes to act on it, the produced hydrogen has to move into porous rocks and then become trapped in an impermeable cap, like shale or salt deposits.
Kansas’s Midcontinent Rift is one such example of potential. Existing here are thick basalt formations that are rich in reactive iron, and here, hydrogen can be produced from the groundwater moving through the basaltic formations and then accumulated in a structure formed during ancient tectonic movements. Another promising location is the Bulqizë ophiolite in Albania, at which 200 tons of hydrogen were measured moving out of a chromium mine each year, this being the highest recorded natural outflow of hydrogen in the world. Browse Stock Photos
“Recipe” comprehension requires the estimation of six key parameters: the presence of abundant groundwater, hydrogen-bearing rocks, temperatures ranging from 250°C to 300°C for faster reactions, and the absence of microbial life. This is possible all over the globe and provides a vast search region. However, the level of exploration is still rudimentary. The single commercial hydrogen gas well is located at the site of the Malian village of Bourakébougou and supplies hydrogen gas for the local fuel cells that generate electricity using only heat and water as by-products.
From an engineering perspective, tapping these reservoirs will require adapting subsurface gas production techniques. Hydrogen’s small molecular size demands careful seal integrity assessment, akin to helium preservation studies, and specialized materials to avoid steel embrittlement in wells and pipelines. Reservoir engineering will need to address potential contamination from co‑produced gases and manage injection‑withdrawal cycles if stimulated production is pursued a method where water is injected into reactive rocks to trigger hydrogen generation.
Clean energy implications are profound. While “gray” hydrogen produced from natural gas requires some 10 tons of CO2 per ton of produced hydrogen, the carbon footprint in the case of natural hydrogen is mostly due to the production phase. Cost projections for the initial projects suggest it could be produced for $0.50-$1.00 per kg. This is significantly cheaper than any other low-carbon method of hydrogen production. If a ‘small’ portion of the estimated global resource is exploitable, it can fuel the world for centuries.
Exploration firms with support from big energy investors are already on the heels of attractive geological targets. The secret to their success will depend on the implementation of this new geological map that combines geophysical mapping, geochemical analysis, and microbiological testing to identify and protect hydrogen pools. Now that the foundation work scientifically is complete, the game is on to convert hidden hydrogen in the Earth into the foundation of the future.
