I saw an article in a mag that had a restored WW2 truck running off the fumes of a wood fire burning wood chips (coal or whatever you have that will burn well) !
It was widely used in WW1 Europe as well.
You light the fire, eat breakfast to let it get going, turn on a fan to get the smoke pulled down into the intake manafold area, crank the engine to start it and drive off!
All you have to adjust it is set the smoke to air ratio and keep the fire tube more than 1/4 full.

There are even plans and sizing chart to tell you how big a diamiter a fire tube you need for whatever HP or CID your engine is!

Be warned, it might not work well on a tiny little Geo Metro as the processor might be a bit big for it, but on a truck it seemed not so big.

I plan to make a stationary unit out of a 215 V8 I'm building just to see it work, then perhaps convert it to work either as a gen set or perhaps if I find a classic truck cheap, it might go in it.

I also saw someone in Australia I think had a processor on a trailer pulled begind a station wagon to carry the wood and cooker for LONG nonstop trips.

The info I gathered is on my daughters laptop, but I googled it and found tons of info.

 

The problem with those is they get terrible miles per pound of fuel. But put one on an offroad trail or remote farm or property and you never have to worry about running out of juice.
I think it would be cool to set one up as a cogenerator. Basically a wood burning stove combined with a generator.
I'd like to see one run on sawdust or some other waste product.

 

But if things turn bad, real bad, with no gasoline or diesel available to run anything, it would be better than the alternative of no energy at all.

Run a generator off the back, and a wood chipper off the front, the system would be self supporting.

 

Mother Earth Mag. has had many atricles about wood gas and even sold plans to make a "cooker" and detailed info on how to mod your carb. I believe that was in the early 90s. It was very interesting. You might want to check them out for back issues and plans.
Also, I remember there were a few groups that built and drove these things across country admid much tv coverage. Most of them had a car that pulled a trailer. Mother Earth Mag had a chevy 6 truck they did their conversion on and they also bult a power generator plant using wood gas to power their compound.
Anyway, something to think about. Seems to me it would be a pain in the but, however if worst came to worst.............