alternative fuel 
noun
A fuel other than petrol or diesel for powering motor vehicles, such as natural gas, methanol, or electricity: alternative fuels have gained ground [mass noun]: vehicles running on alternative fuel...
- In the late '80s and early '90s methanol was the alternative fuel of choice.
- As an alternative fuel, ‘bio-diesel’ is derived from canola, soy, corn, sunflower, etc.
- Even the way cars are powered has changed with the recent rise of diesel cars as well as LPG and other alternative fuels.