OK, guys, I know what she's saying.
Hydrogen is extracted from water by running an electrical current through the water, which is known as electrolysis
. D-Y is arguing that power plants must produce this electricity, and that these power plants pollute, which is essentially correct, given that a large percentage of them in the US burn fossil fuels like coal, which is not a good thing.
Before things got carried away in the other thread, I was under the impression that I had clarified that the first priority would be to completely switch to non-emissive methods of generating electricity, such as nuclear power plants, to generate all of the electricity necessary to produce the hydrogen, which would make the hydrogen truly emission-free. A secondary priority would be to ensure that these methods use renewable resources (or close to it, as in the case of breeder reactors) and that the net cost of the power generated is so cheap that the efficiency question isn't such a big issue.
One source of energy with the potential to solve this particular problem is tidal power
. If constructed with environmental considerations in mind, tidal hydroelectric power plants have the potential to generate vast amounts of cheap (once the construction costs are recovered), emission-free power while making a minimal impact on the environment.