Hydrogen Energy Fuel is not clean energy
Hydrogen isn’t always clean to produce. It’s expensive to pull hydrogen from water. Non-renewable sources of hydrogen, such as oil and natural gas, are much cheaper, but using them still puts a drain on our fossil fuels supplies. Ironically, the carbon dioxide released in the process of producing hydrogen from fossil fuels cancels out any benefits to the environment. Experts say hydrogen that escapes during the production process could erode the ozone layer even further and exacerbate global warming.
To produce usable hydrogen, it has to be separated from water, biomass (plant and animal waste), coal, or natural gas. About 95 percent of the hydrogen used today is produced by a process called steam reforming — separating hydrogen atoms from carbon atoms in methane. This process releases greenhouse gasses, which contributes to global warming.
Source: howstuffworks.com