The hydrogen economy is a term for a economic system in which hydrogen is used to store energy. Burning compressed hydrogen, a chemical compound (H2) could be used in fuel cells to produce energy without carbon dioxide emissions. Instead, water would be produced.
Hydrogen, which is the most abundant of all elements, is found in stars and is a volatile gas on earth.
It is widely believed that the hydrogen economy will replace the current fossil fuel economy where internal combustion engines burn gasoline. However, only a few companies have begun selling hydrogen vehicles and there are a limited number of fueling stations, mainly in the California and Washington DC areas. Hydrogen itself is not a fuel source, but is a carrier of energy. That is, the energy to create the hydrogen must come from somewhere else.
Despite this, a new hydrogen economy would have the advantages of reducing the economic and security risks of importing oil, reducing the risks of environmental pollution (like oil spills, smog and global warming).