Mantle8, the Grenoble France based natural hydrogen exploration company, has raised €31M in Series A funding to leverage its proprietary technology stack across a global exploration and drilling campaign targeting the first commercially exploitable reservoir of high-purity natural hydrogen. The round was led by Sandwater and includes Breakthrough Energy Ventures, Ecotechnologies 2 fund managed on behalf of the French government by Bpifrance, IP Group, Wind Capital and Calderion (an Audacia-backed investment platform).

This capital will be deployed during the next two years to fund the world’s most advanced natural hydrogen exploration and drilling campaign. Mantle8’s novel technology platform, which is tailored to identify commercially viable natural hydrogen reservoirs, will be employed across its global development pipeline to identify and rank the most promising opportunities. These sites will then be drilled to confirm natural hydrogen accumulations and to evaluate volume, purity, and reservoir quality in support of commercially viable, large-scale production.

Hydrogen is a crucial part of our future decarbonized industrial system; however, the importance of its role will depend on its price and origin. Mantle8’s novel technology for identifying commercially viable natural hydrogen reserves reduces exploration risk and cost, with economic models projecting production costs as low as €0.80/kg, significantly contributing to a much lower average cost of clean hydrogen supply. This will fundamentally change the hydrogen sector’s economics, unlocking a low-carbon source of sovereign energy supply for Europe as well as other geographies. By cooperating with partners focused on drilling and exploiting target reservoirs, the technology can be rolled out quickly and at scale.

“This raise reflects the growing conviction among leading clean tech investors that natural hydrogen is a resource worth pursuing at scale,” said Emmanuel Masini, Founder and CEO of Mantle8. “The existence of natural hydrogen is a well-established scientific fact; the challenge has been finding free gas accumulations of high-purity hydrogen that are commercially viable. I’m proud that we’ve built and patented an entire technology stack to answer this critical challenge, meeting the expectations of our existing shareholders” he continued. “The next steps are to identify the prospects in our pipeline that meet our commercial hurdles and drill them. I’m excited to welcome investors who have a long history of involvement in subsurface resources, sovereign investments and ecosystem building.”

“We built Sandwater to back exceptional founder teams with the technical depth and operational rigor to solve critical challenges and deliver solutions that lead to a better future”, said Tom Even Mortensen, Founder and Managing Partner of Sandwater. “Mantle8 is exactly that kind of company. Emmanuel and his team have built truly proprietary exploration technology, validated it in the field, and now have a clear plan to move into the commercial phase. Natural hydrogen sits at the intersection of energy transition and resource discovery, two areas where Europe must lead as it seeks energy sovereignty. This is a demanding challenge but with the potential to create a new clean energy source, which is what we need and why we see in Mantle8 the opportunity for outsized impact and return”

“Geologic hydrogen is one of the most surprising energy developments of the past decade, with the potential to play a significant role in the global energy mix,” said Carmichael Roberts of Breakthrough Energy Ventures. “The Mantle8 team has made impressive progress in advancing its rigorous, geology-driven approach to exploration, and the team continues to execute on targeting the first commercially exploitable reservoir of high-purity natural hydrogen.”

“Natural hydrogen represents a strategic opportunity for France and for Europe,” said Alexandre Wagner, Investment Director at Bpifrance Green Venture. “Mantle8 combines a proprietary exploration technology stack with a clear path to commercialization. Backing this company, aligns with our mandate to accelerate the energy transition through sovereign, low-carbon solutions that could be developed before the end of the decade.”

Mantle8’s Series A follows a period of significant momentum for Mantle8. In 2025, the company raised a €3.4M Seed Round led by Breakthrough Energy Ventures and went on to complete the world’s first 4D imaging of an active underground natural hydrogen system using HOREX® at its Hydrogeco project in the French Pyrenees. Earlier this year, Mantle8 received a €2.06M grant from the EU Just Transition Fund to industrialize its core exploration technologies.

This investment round brings total funding raised by Mantle8 to €37M (US$44M). “With this backing, we will work alongside industrial partners globally to move from exploration through to commercial development”, said Bart Markus, Mantle8’s chairman. “The next two years are about proving that the active hydrogen systems our technology has pinpointed can deliver sustained, commercially viable flow.”