"Hydrogen gas (H2) will play an important role in developing sustainable transportation in the United States, because it can be produced in virtually unlimited quantities using renewable resources. Pure hydrogen and hydrogen mixed with natural gas (hythane®) have been used effectively to power automobiles. However, hydrogen's real potential rests in its future role as fuel for fuel cell vehicles. Hydrogen and oxygen fed into a proton exchange membrane (PEM) fuel cell "stack" produces enough electricity to power an electric automobile, without producing harmful emissions." - http://www.afdc.doe.gov
