Natural hydrogen system evaluation in the São Francisco Basin (Brazil) Vivian Azor de Freitas, Alain Prinzhofer, João Batista Françolin, Francisco José Fonseca Ferreira and Isabelle Moretti Sci. Tech. Energ. Transition, 79 (2024) 95 Published online: 28 November 2024 DOI: 10.2516/stet/2024091