Hydrogen (H2) combines explosively with oxygen (O2) to form water (H2O). The reaction is exothermic, in other words it releases energy. Hydrogen and oxygen have therefore been used as rocket fuel for decades, not because of a benefit to the environment but because the full weight of the fuel is ignited. That the process is clean-burning suggested to some, back in the 1990s, that it would be environmentally friendly to expand its use as a car fuel as well. Though the idea was quickly dismissed on scientific grounds, the idea has experienced a rebirth in recent years.
Proponents of hydrogen as a fuel believe that a switch from hydrocarbons to hydrogen fuel is advantageous to the environment. Specifically, they tout the cleanliness with which hydrogen burns, producing only energy and water. This however, ignores the production end, which is highly pollutant.
About 95 percent of the hydrogen currently produced in the United States comes from natural gas processing called "steam methane reforming." Although the process uses natural gas, production creates a great deal of CO2--the opposite of the impression proponents of hydrogen fuel give.
Other Hydrogen Production
The separation of hydrogen and oxygen by hydrolysis (using electricity) is much less popular than steam methane reforming because it is so inefficient; only about 70 percent. According to the documentary "Who Killed the Electric Car?" a fuel cell car powered by hydrogen made with electricity uses three to four times more energy than a car powered by batteries. This difference is expected to widen as battery technology continues to improve.
Hydrogen leakage can occur during many steps of its production and use. Science Magazine reported in June 2003 that hydrogen leakage from widespread use of hydrogen fuel would gobble up ozone faster than CFCs do. Chlorofluorocarbons are banned worldwide to prevent deterioration of the protective ozone layer.
Hydrogen cars further hurt the environment by distracting from the far greater efficiency of electric cars. Research engineer Wally Rippel of AeroVironment put forth the argument that GM and Shell are pushing forth hydrogen fuel cells as a way to distract the public with a technology that is too far in the future to hurt current demand--and therefore acts to preserve the status quo. In contrast, U.S. Energy Secretary and Nobelist Steven Chu has called for the cancellation of all of the $100M in his DoE budget for hydrogen fuel cell research.
Two possibilities that researchers are pursuing to salvage hydrogen as an environment-friendly fuel are as follows. Argonne National Lab is studying CO2 capture during the steam methane reforming process. And researchers in Australia are working on a solar-driven residential hydrogen pump--creating hydrogen fuel by hydrolysis using photovoltaics on one's own garage roof.