Hydrogen when they get on top of it.
Anti electricity big time as 65% of the current supply is from oil and gas to begin with, so there's energy loss there and down the transmission lines.
Hope for the future - syn petroleum - where CO2 is extracted from the air, concentrated up and then reacted with H2 to create the basic organic building blocks for oil products - effectively meaning that we rent CO2 from the air, not from fossil fuels..... Yep, they're looking at a project at the moment.