The degree to which this technique can fulfil its promise to lower CO2 and provide a sustainable fuel source depends crucially on the balance of energy it requires and the energy it stores.

BBC: Petrol from air: Will it make a difference?

"To me it was clear that depleting natural resources and rising fuel costs make solar the energy source of choice for tomorrow, " the entrepreneur explains.

CNN: Recasting the Mind

Those who are for more widespread use of ethanol said it can improve national security, improve our ability to make home-grown fuel and improve our health by steering us away from an energy source that is becoming increasing harder to get to and dirtier to extract.

CNN: Ethanol: Is it friend or foe?

Chesapeake is looking at natural gas as a potential energy source to fuel its rigs due to the cost benefits and the environment friendly nature of the fuel.

FORBES: Chesapeake Energy Gassed Up For Drive To $36

Mr Salmond's opponents say the Scottish government has cut the fuel poverty support budget - and they argue further that Scotland could not found an economic strategy upon a declining energy source.

BBC: Alex Salmond keeps the faith

"Our vision is that one of these plants would be the core element of a community energy center" that could provide a local, sustainable source of both transportation and heating fuel.

FORBES: Ethanol

And skeptics are also saying that wind energy is an intermittent fuel that must always be backed up by a power source that can begin generating when the wind dies down, making it expensive to operate.

FORBES: Wind Energy Generating A Lot of Mud