The only way you are going to extract hydrogen from tap water is
electrolysis, and the energy input is gonna be higher than the output
UNLESS you have very dramatic improvements in combustion.
The latter I don't know about, but the "hydrogen economy" is a load of
bunk. All commercial hydrogen comes from coal fired electrolysis
plants or processing of natural gas with the release of all the carbon
as CO2. Sure, it will only produce water and electricity in a fuel
cell (that does not currently fit inside a car and costs $30,000 or
so), but you have to MAKE the hydrogen from somewhere -- it is never
free in nature.
Peter
