Table 1 Key energy carriers and the processes for interconversion.

Processes listed in each cell convert the row energy carrier to the column energy carrier. Further details about costs and efficiencies of these interconversions are available in the supplementary materials.

e Electrolysis ($5 to 6/kg H2)Electrolysis + methanationElectrolysis + Haber-Bosch
Electrolysis + Fischer-Tropsch
H2Combustion Methanation ($0.07 to 0.57/m3 CH4)Haber-Bosch ($0.50 to 0.60/kg NH3)
Oxidation via fuel cell Fischer-Tropsch ($4.40 to $15.00/gallon of gasoline-equivalent)
CxOyHzCombustionSteam reforming ($1.29 to 1.50/kg H2) Steam reforming + Haber-Bosch
Biomass gasification ($4.80 to 5.40/kg H2)
NH3CombustionMetal catalysts (~$3/kg H2)Metal catalysts + methanation/Fischer-Tropsch
Sodium amide