Mantle8 is a Grenoble company founded in 2019 that uses geological analysis and subsurface data to predict where natural hydrogen forms and accumulates before drilling. Its backers include Sandwater, Breakthrough Energy Ventures and Bpifrance. In October 2026 it organised an open letter from more than 30 organisations asking the European Commission for a €1 billion programme to drill about 50 exploration wells across at least 10 member states.