Well E85 is 85% ethanol which (IIRC) in this country is made from corn – so, if you buy a flex-fuel vehicle you could run mostly off of ‘corn fuel’. Of course they don’t tell you your fuel mileage will suffer by about 50%………but it’s not 50% cheaper to buy.
Diesel is the other option, and back when it was invented it was actually made to run off of peanut oil, not the petroleum product. There’s a whole controversy behind that and the untimely death of Rudolph Diesel after which the oil companies said the engines would only run off of fuel made from crude oil.