Another reason why the hydrogen economy will never happen.
It makes more sense to use methane from rotting garbage (not just from poo, but anything that rots) to generate electricity, and then use that electricity for whatever than it is to generate electricity for the purpose of making hydrogen, using more electricity to compress, store and transport hydrogen... only to have the hydrogen converted back to electricity for an electric motor to use.
Or the methane can be used to heat homes (it isn't much different from the Natural Gas already being used) or it could be used directly in cars and trucks... though that would be less viable and of limited appeal for the same reasons why CNG and Propane vehicles have limited appeal... the explosion factor, the vehicle conversion cost factor, a lack of fueling stations and limited range.
And you could overcome the limited range through a dual fuel setup... but then you have an engine that isn't optimized for either fuel.
But to do this would require a change in how we handle sewage and garbage. Energy prices need to be high enough to justify the cost.
At the moment, some sewage-related utilities are already running their trucks on methane (sewer gas).