The green transition may have found its catalyst beneath the ground in Lorraine, France: a vast deposit of 46 million tonnes of white hydrogen. This discovery is the latest development in a global exploration boom that began in Africa over ten years ago – a gold rush that promises to deliver a clean fuel for less than a dollar per kilo.
Grey hydrogen and green hydrogen
For decades, the industrial sector has viewed hydrogen as the ideal energy carrier for decarbonising hard-to-abate sectors, from steelmaking to aviation. However, production has come up against an insurmountable paradox. ‘Grey’ hydrogen, produced via steam reforming of methane, is cheap but highly polluting. ‘Green’ hydrogen, generated by the electrolysis of water, requires enormous quantities of electricity from renewable sources and suffers from significant efficiency losses throughout the supply chain. Today, geology offers a third way: the direct extraction of geological hydrogen, naturally accumulated in the Earth’s crust.
White hydrogen: the story begins in 1987
The global hunt for ‘white hydrogen’ began in the small village of Bourakébougou, in Mali. In 1987, whilst drilling a water well – which was subsequently sealed – a worker accidentally caused an explosion by holding a lit cigarette close to the borehole. Subsequent chemical analyses, carried out years later, revealed a gas stream consisting of 98 per cent pure hydrogen. Since 2011, this pilot field has been powering the village’s generators without producing any carbon dioxide emissions, demonstrating to the world that molecular hydrogen can accumulate in stable underground reservoirs and does not inevitably disperse into space, as was previously believed. The case of Mali has shattered old dogmas, transforming academic scepticism into the current ‘white gold’ rush. Predictive models from the US Geological Survey estimate that the Earth’s crust contains thousands of billions of tonnes of geological hydrogen.
White hydrogen is not a static fossil resource, but the product of a dynamic and regenerative system fuelled by two main geochemical macro-processes: serpentinisation and the radiolysis of water. Serpentinisation occurs when rainwater percolates into the subsoil, coming into contact with ultrabasic igneous rocks (peridotites), rich in olivine and iron-bearing minerals. At temperatures ranging from 200°C to 300°C, the iron is oxidised by the oxygen in the water molecules, forming magnetite. This process of spontaneous oxidation – a veritable underground rusting process – breaks down the water, releasing enormous volumes of hydrogen gas.
Radiolysis, on the other hand, is linked to the presence of naturally occurring radioactive elements such as uranium, thorium and potassium in crustal rocks (such as granites). The ionising radiation emitted by nuclear decay breaks the chemical bonds of the water trapped in the rock’s pores, releasing hydrogen. Once generated, the gas migrates upwards through faults and tectonic fractures, but if it encounters impermeable ‘geological traps’ (such as evaporites or clays), exploitable deposits are formed, such as the one discovered at Folschviller, in Lorraine.
