Hydrogen fueled cars, just like electric cars, aren't zero-carbon per se, it all depends on where the energy comes from to produce the fuel. If the energy is produced from renewables then yes, it's zero carbon, but if the energy is generated conventionally then no, it has the same carbon footprint as petrol. So it's quite possible to have a hydrogen car with a carbon footprint, and a bio-diesel car with no carbon footprint. What we really need is a renewable source of energy, and particularly one that doesn't compete with food crops for land resource, though of course it does no harm to invent hydrogen-storage technology so we don't all drive around in little Hindenburgs. Wind power is not a bad way to generate hydrogen fuel because one of the problems with wind power is that you can't rely on the wind to blow, so you just stockpile the fuel on windy days.