Renewable Alternatives To Oil Viable At $60/barrel
They were doing research on this at AU and many other universities while I was there. Don't know how inflation has affected those estimates, but oil has closed the gap a lot. You can make fuel from biological byproducts that are normally wastes from food and paper processing or even grow crops specifically for conversion like corn to ethanol. The end of oil is not a wall, but it would be a big economic bump. It probably won't be that steep though as interest and research will rise as the cost of oil goes up so there will probably be a gradual phase in rather than a crisis followed by rapid research and implementation.
Regards,
Mark