What will power the "future car"?

According to most energy sages, hydrogen-powered cars will be what most of us are tooling around in several decades from now. But you don't just drill in the ground and pump out hydrogen; it has to be extracted from another source.

Hydrogen is the most abundant element in the universe and is found in many, many different molecules. Thus, it can theoretically be extracted from a wide variety of sources. But the favored sources, at least for now, are:

• water;
• natural gas, particularly methane;
• coal, via coal gasification; and
• biomass (vegetation such as wood chips and agricultural waste).

The processes for extracting hydrogen from these sources are different, particularly in the case of water. To get hydrogen gas out of water, electrolysis is used—that is, electricity is employed to strip the hydrogen molecules out of the water. Comparatively, in the case of natural gas, a "reforming" process is used.

However, no matter what the source of the hydrogen, the process requires electricity and/or other types of energy. Additionally, in the cases where fossil fuels or biomass are used as the sources, the substrates are power-plant fuels themselves, which sets up a sort of competition between using them for generating electric power and generating hydrogen.