[reg45]

I have been an advocate of hydrogen as a fuel for over forty years; either in a fuel cell or in an internal combustion engine.

[Reeses]

after all the only emissions are water vapor

Which happens to be the number one greenhouse gas.

Hydrogen molecules are tiny and are going to leak constantly into the atmosphere, for example at the refueling point. Because hydrogen is lighter than all other atmospheric gasses it floats up into the sky where it then reacts with the ozone layer, eating it. Hydrogen may work for small scale projects but is never going to work as a mass market fuel.

[Foundahardheadedwoman]

‘I have been an advocate of hydrogen as a fuel for over forty years; either in a fuel cell or in an internal combustion engine’
I believe it will come down to a horse or shank’s mare. Since horses give off gases and solid waste the EPA will promptly make them illegal. I guess shank’s mare will soon be the only option, except of course for our government overseers.

[backwoods-engineer]

I have been an advocate of hydrogen as a fuel for over forty years; either in a fuel cell or in an internal combustion engine.

Well, then you have been blinded for 40 years. Hydrogen is an energy-storage medium, not a fuel. Where can you drill for hydrogen? Even if you skim it off a gas giant, or the Sun, you need energy to compress it, cryogenically store it, and bring it back.

Hydrogen as a fuel is a fool's errand.