It may seem odd, to some, but internal combustion engines can be run on gas produced from plain old wood. The practice was somewhat common in petroleum starved axis countries during World War II. The trick here is gathering up all the parts and doing all the welding BEFORE the you go through an energy blackout.
One important thing to note is that the process basically pressure cooks the wood. This can be an extremely risky affair since the device has a home made potential bomb built in.
For more information on wood gas
The Hard Tack Brigade 