The answer should be Hydrogen I just got finished reading about a fireplace that uses water for fuel. What they do is apply some kind of electrolisis to the water that separates the Hydrogen and Oxygen. They burn the Hydrogen use part of the Oxygen to enhance the fire and send the rest into the room. The by-product is water vapor. It doesn't need to be vented. Now it Cost $50,000 for a unit manufactured by I think Heat n Glo or whatever. They didn't say how much electricity was used to break down the water though. Toyota is also planning to build a Hydrogen powered car. They already are selling hybreds that run on gas and electricity(two separate engines) the electricity is generated from the gas engine and from the movement of the vehicle and is then stored in batteries that supply the electricity to the electric engine.
Wouldn't it be great if we could go to sleep now and wake up unaged a thousand years from now. That's if we don't all kill each other over something stupid like who gets to control the Oil. We are spending a ton of money to fund a war so that we can protect that oil when with all that money we could have already developed some practical solutions using Hydrogen which has the potential to save a ton of money that can be used to make earth a better all around place to live for all its inhabitants.
