[E. Pluribus Unum]

"We can dig up petroleum, but hydrogen has to be created from, say, seawater. And that requires a lot of energy."

And that energy comes from...

PETROLEUM!!!!

[Physicist]

And that energy comes from...

PETROLEUM!!!!

But not necessarily. Petroleum is an expensive power plant fuel. The cheapest thing right now would be to build fission reactors (and they won't have to be near populated areas this time). Ultimately, coal represents the greatest available store of energy.

[AppyPappy]

And that energy comes from...

Coal, wind, solar and nuclear.