天然水素の流出率と生産の実行可能性の関係

Despite the widespread occurrence of mostly low concentrations of molecular hydrogen (H₂) in nature, the quantity of commercially recoverable natural hydrogen underground remains uncertain. Two production variants are conceptually considered: a self-replenishing system, in which underground generation balances off-take; and accumulation systems, in which H₂ is trapped underground over long periods and is extracted similarly to conventional natural gas deposits. To assess the potential of natural hydrogen, we compiled and harmonised global data on H₂ flow rates, flux rates, and concentrations from various sources like seeps, springs, mines, and wells. Across different geological settings, observed large natural H₂ flow rates typically fall between 10⁵ and 10⁷ cubic meters per year (m³/yr). When comparing these values to the output of producing natural gas wells and economic viability thresholds for modelled H₂ projects, we find that commercially viable rates must be at least an order of magnitude higher (≥ 10⁷-10⁸ m³/yr). Furthermore, sustained production at high hydrogen purity over two to three decades is generally required for commercial success. Based on this analysis, we argue that economically recoverable natural hydrogen from self-replenishing systems is unlikely.