Earlier this year, Professor Jacques Pironon and his team, while on a quest for methane in the Lorraine Basin, northeast France, stumbled upon an unexpected treasure – a vast deposit of hydrogen lurking around 3,000 meters underground.

"It is what we call serendipity," says Prof Pironon, research director at France's Centre National de la Recherche Scientifique (CNRS) at the University of Lorraine.

Not long ago, such a discovery might have been confined to academic interest, but in today's context, it sparks excitement.

Hydrogen is gaining recognition as a potential key player in achieving a net-zero global economy, as it does not produce CO2 when used as a fuel or in industrial processes.

However, the major drawback is that the current methods of hydrogen production are not environmentally friendly. According to the Carbon Trust, less than 1% of global hydrogen production is emission-free.

Various types of hydrogen exist, including grey, blue, black, and green. The most elusive is green hydrogen, generated through the electrolysis of water, but it remains expensive and in short supply.

The recent discovery in France involves natural hydrogen, found through the interaction of ground water with iron-rich minerals. This process splits water into oxygen and hydrogen, creating a potential emission-free source.

While natural hydrogen discoveries aren't entirely new, the French find is considered the largest-ever naturally-occurring deposit, estimated to be around 250 million tonnes – enough to meet global demand for over two years.

Prospects for additional undiscovered hydrogen deposits worldwide are high, with the US Geological Survey suggesting thousands or even billions of megatonnes. However, not all may be readily exploitable.

Efforts are underway to tap into these resources, with commercial ventures and exploration projects in Mali, the US, Australia, Russia, and various European countries. Bill Gates's Breakthrough Energy Ventures and other firms are investing in startups focusing on hydrogen exploration.

While major energy players are currently cautious, industry experts believe that once production data becomes available, significant oil and gas companies will likely enter the hydrogen market. However, challenges remain, such as the lack of a robust hydrogen market in certain regions.

The future of hydrogen as a widely adopted fuel source may depend on concerted efforts to develop both supply and demand, overcoming the current "chicken and egg problem," as Geoffrey Ellis, a USGS research geologist, points out.

"I think it's a function of how much effort we put in. If we really decide this is something we need to figure out quickly, I think it could be done," he concludes.<