Currently, hydrogen is considered a carrier of energy rather than a source—i.e., not produced naturally as are fossil energies, but as the product of converting other resources. The H₂ used in industry is mainly produced by converting natural gas (CH₄), which has the downside of emitting CO₂. In the future, hydrogen produced through water electrolysis is expected to be used to store energy as a way of compensating for solar or wind power’s intermittent output.

However, IFPEN says, growing evidence is pointing to the existence of substantial, natural generation of hydrogen. This could forces a change of paradigm, the R&D group says. In addition to being a carrier of energy, hydrogen could also be a source of energy, and its combustion would emit water (H₂O) instead of CO₂.

While “natural” hydrogen does indeed exist and can be qualified as a clean source of natural energy, the question now being asked is whether it is sustainable. This is currently the focus of IFPEN’s research.

Natural emanations of hydrogen were first discovered along mid-ocean ridges on the seabed (“black smokers” and “white smokers”). A mid-ocean ridge is the divergent boundary between two tectonic plates forming a submarine mountain range and is the site of volcanic activity that creates the seabed.

Some 64,000 km (40,000 miles) of ridges demarcate plate boundaries on the ocean floor. The Mid-Atlantic Ridge, which separates the Eurasian and African plates from the American plates, is the longest of these and stretches 7,000 km (4,300 miles).

In this environment, volcanic systems create hydrothermal circulation, bringing together sea water and peridotites at high temperatures. Peridotites are rocks derived from the Earth’s mantle, consisting mostly of olivine (up to 90%) and pyroxenes (ferromagnesian minerals). These minerals contain reduced iron, which oxidizes upon contact with water to produce hydrogen. Peridotites are exposed in some places on the surface of the deep sea floor. Continental exposures are found in particular tectonic environments.

However, these “smokers” are located at deep sea level far from the coasts, and exploiting them is not economically viable.

IFPEN has therefore focused its research on more accessible, onshore sources of H₂, which have been observed in two geological settings:

• terrestrial mountain ranges containing peridotites, where specific tectonics expose the mantle-derived rocks to alteration by meteoric water; and

• intracontinental regions (intraplate regions) and in particular in the oldest parts (Precambrian cratons) located at their center.

While scientific literature makes occasional reference to these hydrogen emanations, until now they have never been explored in detail. IFPEN’s initial research showed the existence of major local flows of H₂ in major peridotite mountain ranges all over the world. More importantly, it demonstrated hydrogen flows were a common feature in intraplate regions.

Intraplate regions are areas located in the interior of a tectonic plate as opposed to an area at a plate boundary. Here interactions with the Earth’s depths are more limited than those at the plates’ boundaries. These areas contain the oldest parts of the continents, cratons.

Despite the flows being sparse on most sites, substantial local accumulations were identified in some areas. The various natural fluids studied can present up to 80% of H₂. It is often associated with methane, occasionally nitrogen and, in some places, economically viable quantities of helium (at a time when demand for this rare gas with numerous high-tech applications are stretching global supplies to their limit).

IFPEN is examining two possible explanations of onshore hydrogen:

• oxidization of rocks rich in reduced iron by water; and

• continuous outgassing by the Earth, which would significantly alter conceptions of the chemical composition of terrestrial planets’ interior structure.

IFPEN will continue its work as part of a new project to assess the technical and economic viability of industrial natural H₂ production. Particular interest will be paid to cratons, which cover very large areas, and may prove promising for production.

If natural hydrogen exploitation were indeed possible, it could constitute a new source of sustainable energy—as production seems to be a continuous phenomenon linked to the Earth’s tectonics—as well as being clean and environmentally friendly and evenly distributed between the continents. Large-scale industrial production, however, remains a long way off, and further research efforts are needed to determine if this is possible, IFPEN says.

Resources

• Valérie Beaumont, Christèle Vacquand, Eric Deville, and Alain Prinzhofer (2013) Hydrogen generation during serpentinisation in ophiolite complexes: A comparison of H₂-rich gases from Oman, Philippines and Turkey. Geophysical Research Abstracts Vol. 15, EGU2013-5553