I'd like to hear Weisshaupt's take on this.
Okay, you asked for it :>)
From what I can tell this is basically the distillation of wood- we did this in my 7th grade science class. So yes, you can get a nice explosive gas from doing this, and it its a perfectly viable fuel source.
http://en.wikipedia.org/wiki/Gasificationhttp://en.wikipedia.org/wiki/Wood_gas_generatorHowever you should consider:
1) the compression ratios in most engines will be wrong. If I were to do this, I would expect to have to do modifications on the engine to get a good result - but LP based machines might be okay with minor adjustments. Like running on alcohol, significant engine adjustments will probably be required.
2) Storage. Energy storage is always, always, always the major problem. Mostly this is H2 we are burning, and H2 is small. Really Small. It likes to get out of whatever container you put it in - so much so that when most humans store it, they do it in a liquid form, in a pressure container. You can make synthgas out of this.. and store that, but that is a whole other process.
3) Purity. - but given the source material you are going to get all sorts of other stuff too - which, over time will gum up the filters, or worse, it can get in the engine. If the filter doesn't prevent the larger oils and chemicals from getting into the engine, its going to tar things up. The long term effects on the engine of running a fuel it wasn't designed for may require more maintenance than you want. The engine running too hot/cold or with potentially corrosive gases ( trees contain a lot of things that can become caustic) is going to not do well over time. Of course in a real teotwaki situation, you do what you gotta do.
4) Feedstock.. this is fuel conversion is going to work best with chips, so you need to reduce your feedstock into that form by some method. Yes a Wood Chipper will work fine-- but what are you fueling that with?
5) Carbon Monoxide. Lots of it.
So as a backup/alternative to Solar, this is fine, providing the output is clean enough to not F' up your generator. I would still prefer Solar because it requires almost no attention and has fewer moving parts.
For a Propane/LP alternative you would need the high pressure equipment to take the gas and push it into the pressure tank - and then you may have to modify any appliances you have to get the right air/fuel mixture.
For heat/Hot water? Again, I don't see the need. A modern wood pellet stove does essentially the same thing.. though I would be interested on seeing the efficiency numbers of this process. This article suggests in large scale systems, its a difference of 30 to 36% for electricity production , and 62% and 82% if you are also using the heat. - which should put it in the same range as your typical modern stove (70-80%) without the need to get the fuel really, really hot, or to chip it up. And those are large scale numbers.. I suspect small scale numbers are going to be worse.
http://www.biorefine.org/proc/biomassgas.pdfBut maybe not.. this company claims a 87% conversion - which is probably 10% better than a wood stove, with hot water thrown in.
http://www.alternativefuelboilers.com/searchlanding.html?gclid=CLmRpoz5taoCFQVrKgodwD6m7wHowever, I suspect probably just easier throwing another log on the fire in a normal stove. Water heating can also easily be done with solar, using a pretty cheap DYI system - and again, its one of those set it and forget it kind of things-- especially if you have an automatic alternative to heat the water on days when the sun isn't co-operating... but that brings us back to the propane.
I would be very wary of using this on a vehicle - especially one you plan to depend upon. You need to know the fuel is clean...
As with all of these newbie/greenie tech, the companies supplying this are questionable. In a brief search I didn't find any that really seem to have a handle on it..
These guys seemed the "best"..
http://victorygasifier.com/ - offering what appear to be polished, turnkey systems.. but they don't seem to list prices ( always a worrisome thing to me) and they have a $500 "mentoring" program if you need more than a few hours of support. (and if their product was that good, why would they need that? )
However, there seem to be some industrial companies that might be more viable ( and expensive)
http://www.chiptec.com/index.html#productsSo in summary, yes this is a viable Teotwaki technology, but to my mind it has significant limitations compared to other methods.. - in particular with the energy storage. Yes, you could mount one on your vehicle, spend 10 minutes firing it up, and load the hopper with about a pound of biomass for every mile you plan to drive. Or you can produce ( and STORE!) biodiesel or alcohol..
All of this is also going to depend on what you are planning for. If you think there is going to be a Max Max scenario - yes you probably need one. If you instead just see us declining into the third world, then there will be people producing synthgas, alcohol, bio-diesel if the Oil becomes unattainable or too expensive. I am not aiming for 100% independence... and I still think a liquid fuel is the way to go for vehicles , but I may be wrong :>)