When the Nebula was formed it was almost pure hydrogen.

Because pure hydrogen does not occur naturally, it takes energy to manufacture it.

It is also the most common way to make pure hydrogen, used in fuel cells.

Nucleosynthesis - building up higher elements from pure hydrogen.

When powered by pure hydrogen, fuel cells have none of the environmental problems associated with gasoline.

If the fuel cell is powered with pure hydrogen, it has the potential to be up to 80-percent efficient.

If the fuel source isn't pure hydrogen, then the vehicle will also need a reformer.

A minibus operated on pure hydrogen was demonstrated in 1977.

Insiders suggested that rather than use pure hydrogen, these might be direct methanol powered.

Fuel cell cars are not truly emission-free, because it takes energy, and emissions, to create pure hydrogen.