- French natural hydrogen startup Mantle8 raised €31M in Series A funding, bringing total funding to €37M.
- The round was led by Sandwater with participation from Breakthrough Energy Ventures, Bpifrance, IP Group, Wind Capital, and Calderion.
- The company will use the funding to expand its global exploration and drilling programme for natural hydrogen reservoirs.
French Mantle8 has secured €31M in Series A funding to scale its natural hydrogen exploration technology and drilling operations. The investment brings the company’s total funding to €37M, including a €3.4 million seed round raised in 2025 and a €2.06 million EU Just Transition Fund grant received earlier this year.
The round was led by Sandwater and included backing from Breakthrough Energy Ventures, the Ecotechnologies 2 fund managed by Bpifrance on behalf of the French government, IP Group, Wind Capital, and Calderion.
Founded in 2019 in Grenoble by geoscientist Emmanuel Masini, Mantle8 develops subsurface modelling and exploration technologies for detecting natural hydrogen. Its core platform, HOREX, produces 4D images of active underground hydrogen systems.
“Natural hydrogen exists, but the challenge is finding commercially viable high-purity reserves. We’ve built and patented a technology stack to solve that challenge, and the next step is identifying and drilling the best prospects in our pipeline,” says Masini.
The company estimates its technology could reduce hydrogen production costs to around €0.80 per kilogram. It also plans to expand its global development pipeline through partnerships focused on drilling and reservoir exploitation, supporting large-scale hydrogen production in Europe and other regions.
In 2025, the company completed what it described as the world’s first 4D imaging of an active underground natural hydrogen system at its Hydrogeco project in the French Pyrenees.
The company also uses its Geological Trifecta framework to identify reservoirs where hydrogen generation, continuous replenishment, and sealed geological structures align. Mantle8 claims that this reduces exploration risk and lowers production costs.
Mantle8 operates in the growing natural hydrogen sector alongside companies including Koloma, Gold Hydrogen, and HyTerra, but differentiates itself through its proprietary 4D imaging technology and geology-driven exploration framework designed to reduce drilling risk and improve reservoir accuracy.
“We back founders solving critical challenges with strong technical expertise. Mantle8 has developed proprietary exploration technology, validated it in the field, and is now moving toward commercialisation. Natural hydrogen could become an important clean energy source as Europe pushes for greater energy sovereignty,” says Tom Even Mortensen, founder and managing partner of Sandwater.
“Natural hydrogen represents a strategic opportunity for France and for Europe. Mantle8 combines a proprietary exploration technology stack with a clear path to commercialisation,” adds Alexandre Wagner, investment director at Bpifrance Green Venture.
The capital will fund a two-year exploration and drilling campaign focused on locating commercially viable reservoirs of high-purity natural hydrogen. Mantle8 plans to use its technology platform to identify, rank, and drill promising sites while evaluating hydrogen volume, purity, and reservoir quality.
