I would just try the destructive distillation process. Put sawdust in a metal still and condense the vapor. A similar method is used for a gasifier, except the "wood gas" coming from the output of the still is flammable and burned immediately. If you do manage to condense it into a liquid, you could try cleaning it up with a heptane or diethyl ether wash, but this would probably defeat the purpose of making an easy and self-sustaining fuel. Alum might flocculate some of the impurities? Other than this, you could try filtering through carbon. I know that compressed wood gas is unstable and cannot be stored. Not sure what liquid components you might get out of this, though.