“Green” hydrogen, produced with renewable energy, will be an important tool for decarbonization. We need to use this tool correctly, in places where it is the only answer. We talk with an expert about the best uses of green hydrogen.  We can begin by replacing the ‘grey’ hydrogen (derived from methane) already being used in many industries. That would be a big step all by itself. Then we can look at steel, shipping and maybe even airplanes- if battery technology doesn’t get there first.