I drove 1800 miles in a Hydrogen Car

Zero emission means ZERO emission however there are still 'things' being emitted out of the exhaust, good or bad. Plus there are still emissions to produce and transport the hydrogen. 
Only a pure electric vehicle (after manufacturing etc) produces Zero emissions, that is, if it was charged by solar or another power source that does not create a by product. 
This is still a great leap in technology which will only assist humanity in exploring even better systems.