[Diesel_Dave]

Gasification is a pretty cool process. When wood (or other biomass) burns in a flame it's actually a two stage process. The solid doesn't actually burn. In the first stage, the heat turns the chemicals in the solid into a gas. In the second stage, the vapors (gas) burns. That's why when you see a log burning, the flame is primarily above the log, not on the log.

Gasification basically separates the two steps. The gasifier heats the wood without enough oxygen to allow ignition. That way it only converts the solid into a gas (primarily hydrogen and carbon monoxide). You can then burn the gas in an engine, just like natural gas or propane.

You can actually make a simple "gasifier" to see it work. I did this a while back. Get a short large steel pipe (like 2" dia x 6" long or so), a pipe cap, a reducer, and a small pipe (like 3/8" dia x 12" or so). Put some wood chips inside the large pipe. Screw on the cap and the reducer. thread the small pipe into the reducer.

Now put the big pipe in a open fire (campfire or open stove) with the small pipe sticking out of the fire. After a few minutes you'll see steam coming out of the small pipe. A minute or two after that, you'll see the gas coming out of the pipe become less white. This is because the water is all gone and the actual gasification is happening. At this point you can actually take a lighter and ignite the gas coming out the pipe. It looks like a little torch. Pretty cool.

After you're done, open up the pipe and you'll see all the carbon is left. That's how charcoal is made. In a true gasifier, even that will get gasified.