Need alternatives to gas.

What else can I run my car on.  I am not paying these gas prices any
longer.

I understand I can use straight alcohol, but I first need a source,
and then I believe the carburetor needs to be modified (how)?
(this is an older car with carb, not fuel injection).

I also have access to lots of free manure.  I understand it can be
made into methane gas, but I think that is pretty complicated.

I've got a woods filled with downed trees.  I recall once hearing of
cars that run on burning wood.  Does that require a special engine, or
is there a way to extract the gasses from the wood fire and run a
standard engine?  

Dont mention electric cars or hibrids.  Cant afford them !

One other option is propane, but I imagine that is way up in price
too.  Plus, I'd imagine this would require a major engine
modificiation.

Yes, I am already riding my horse more, but to go long distances, I
still need the car.

Any suggestions?

Mark