Don't know about french fries, as the oil is not *supposed* to be the major energy content e.g. in McD's french fries, approx 42% of the calories is from fat, but I'd certainly bet on getting more energy out of a field-full of corn by converting it to ethanol (assuming anerobic biomass digestion of the waste to provide gas to fuel the distillation) then fuelling an IC engine powered generator than by feeding it to a room of BBC cycieists powering pedal generators.