One thing both Honda and General Motors have in common is a belief that fuel-cell cars make sense, even using today’s non-renewable hydrogen supply. Both cite the number of cars that could be run on hydrogen today: Honda says there is enough hydrogen production capacity in the United States to fuel over 1 million cars with no additional investment. Total worldwide hydrogen production is enough to fuel 200 million cars, according to GM (assuming it wasn’t needed for anything else).

Most hydrogen today is produced from methane, a type of natural gas, using steam-methane reformation, a process that producers claim is 80 percent efficient. (The methane also powers most of the hydrogen production plants.)

And fuel-cell cars are about twice as efficient as gasoline-fueled cars. Honda would not give an estimate of fuel economy. But if the FCX can go 270 miles on 4 kilos of hydrogen, that amounts to about 68 miles per kilogram. A kilogram of hydrogen has roughly the same energy as a gallon of gas, so that is the equivalent of about 68 mpg.

Honda claims fuel cells can reduce greenhouse gas emissions overall by 50 percent compared with gasoline, even using today’s hydrogen supplies.

What’s attractive about hydrogen is that, unlike oil, it can be made from just about any organic substance or even from water. Making it from water, however, using electrolysis (which is roughly the reverse of how fuel cells operate), requires so much energy that electricity production would have to increase several fold. It would effectively have to come from renewable solar, geothermal, or wind power sources, which are scarce today. Until now, this has been the vision of many fuel cell advocates.

Finding a way to make enough hydrogen to eventually supply every corner gas station economically is a huge challenge. But fuel cells are so efficient that it looks like we’ll soon see at least a few cars using hydrogen from natural gas as one of several alternatives to increasing oil consumption.

If that’s not “green” enough for you, Honda is studying using hydrogen taken from waste methane at land fills. And GM filled the Sequel we drove with hydrogen generated as a byproduct of chlorine production at a Rochester, New York, plant powered by renewable electricity from Niagara Falls.

Using such renewable sources of hydrogen in large quantities would bring the efficiencies of fuel-cell driving much closer to fruition than they have seemed before. And as our drives of the Honda and GM fuel cell vehicles showed, driving clean, quiet, and powerful fuel cell cars doesn’t sound unpleasant at all.

Learn more about fuel cells and alternative fuels in our fuel economy special section.

--Eric Evarts