Wood gas or Producer gas is a very old form of fuel that is easy to produce and use. It consists of partially combusting biomass, and then burning the smoke and gas as a fuel. It sounds stranger than it really is, and can be done on a budget. In fact, most implementations of wood gas are due to budget or fuel supply issues. Production of woods gas involves a gasifier unit, where the incomplete combustion takes place, and then a filtration unit to filter out the tars and ashes from the gasifier, and delivery to either a burner or an engine.

There are many types of gasifiers, depending on the fuel used and the desired effects. Most camping gasification stoves use a top loading downdraft type of design that is basically one tin can inside another. These designs are great for batch loads of fuel, but for a continuous burn, you will want a hopper loaded downdraft type, like an Imbert design or possibly even a cross draft, if you are using it as a furnace. For fueling an engine, the gas must be very clean, to avoid tar buildup in the engine, and that's where the Imbert style downdraft works very well. Very little tar is produced with this design, so your filtering is less complicated. Also, a wide, rather than tall hopper, as in the moderator design, will allow the use of green or high moisture content fuel.

Once you have a gasifier design picked out, you will need to think about filtering the produced gas. If you are powering a furnace or heater, no need to filter, just burn! For an engine, though, filtering is the most important issue. Cyclone filters combined with a fabric or mesh filter will work well. Cooling the gas is also important, because it precipitates the tars and moisture out of the gas. So, run it through a serpentine pipe or a radiator as well.

To actually burn the gas in an engine is quite easy. Basically, you create a gas carborator, which allows air and wood gas to mix before entering the engine. A butterfly valve on the intact will allow you to throttle the supply of fuel. Most systems require a blower to get started, to pull the gas through the system to get to the engine. The other alternative is to start the engine on gasoline and once it has warmed up, switch to wood gas. This is tricky to do, but once you get used to it, it works well.

Wood gas is not a fill up and go type of fuel. You have to start a small fire in the gasifier, and then once that gets going, shut down the air intake to the gasifier and start the engine or blower. Your engine will loose about 20-40% of its power by running on wood gas, so you have to keep that in mind. For stationary applications, like a generator or chipper, it works quite well.

Wood gas is a useful replacement for wood in home heaters or furnaces. That lovely fireplace in the living room is beautiful, but very inefficient. By converting to wood gas, you can increase your efficiency several times, often tripling the heat output compared to the fuel input. This means less fuel to haul and process. Another great thing about gasification is that you can use all sorts of fuel sources from corn cobs to wood chips to paper to even plastic and tires! Anything that has oxygen, hydrogen and carbon will work, although some fuels are easier.

Wood gas should definitely have a place in your fuel supply, especially if you current use wood or biomass for heat. The leftover byproducts are fine for the compost or garden, and you can enjoy less work for more output, which is always good!

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