Wednesday, July 9, 2008

How Gassifiers Work

As noted before ("Gassify Me"), this is about the simplest wood-burning stove that’s worth building. This stove is extremely simple, much more so than a can with a battery and computer fan, but yet it is also extremely sophisticated, and still has absolutely no moving parts whatsoever.

The operating principle of the wood gas stove is that burning wood produces smoke, and it is also actually not the wood but the smoke that burns. The stove is dead simple. Once you get it built, that’s it – nothing to adjust or maintain. In preparing a new book ("Make Your Fire", which is an excerpt of the stove making part of "Fire in Your Hand"), I edited a diagram I found elsewhere to show the principle this stove works on.

Light it at the top and the wood burns from the top down. The heat of the flames at the top vaporizes the wood below the flame, and the open bottom of the stove allows fresh air to rush in and create a strong updraft. Additional air holes near the top of the stove mix in more air. All these vents, combined with keeping the cooking pot two inches or more above the top of the stove allows complete combustion.

When loaded, lit, and used properly this stove will burn almost without smoke, totally unlike the average wood fire or can stove, which has to be constantly tended, and which smokes constantly.

The wood gas stove burns cleanly, and quiets down from a roaring blowtorch to a cool smolder once all the volatile gases have burned off. At the end you get a clean, warm charcoal glow, which eventually burns out, leaving a little clean ash behind.


Fire In Your Hand (at Amazon).
Fire In Your Hand (at
Zen Backpacking Stoves.
ZZ Manufacturing, Inc. (Sierra stove).