The Hydrogen Economy The world's fossil fuel reserves are being depleted at an alarmingly fast rate. Faced with this dilemma, scientists have made intensive efforts in recent years to develop method of obtaining hydrogen gas as an alternate energy source. Hydrogen gas could replace gasoline to power automobiles (after considerable modification of the engine, of course) or be used with oxygen gas in fuel cells to generate electricity (see p. 786) One major advantage of using hydrogen gas in these ways is that the reactions are essentially free of pollutants; the end product formed in a hydrogen-powered engine in a fuel cell would be water, just as in the burning of hydrogen gas in air of course of a hydrogen economy would depend on how cheaply we could produce hydrogen gas and how easily we could store it.