Wood Gas! Wood Gasification Powers This Truck

Enlarge Image Image Gallery You can run a truck on alternative fuel with a wood-gas generator by using wood scraps or firewood for fuel. This article includes detailed diagrams, photographs and how the wood/gas generator was constructed. MOTHER EARTH NEWS EDITORS

1,500 miles of alternative, free-fuel driving, and there's a lot more where that came from: We were pleased to report in Homemade Motor Fuel ... From Firewood that our experiments concerning the use of wood scraps for vehicle motor fuel showed promise. But little did we realize, at that time, just how well the unlikely form of "solid" energy would work in a "liquid" world.

In short, for a total cost of about $125 — and a fair amount of cutting and welding — we've come up with an alternative fuel power system that not only moves our rig down the road as smoothly and reliably as any conventionally powered automobile, but does so at zero fuel cost!

(Click here and here for a downloadable version of the contruction illustrations.) 

A Straightforward Process: Using Wood as Fuel

Here's how the system works: Wood scraps (we use chunks that are larger than sawdust or shavings, but smaller than a 6" length of 2 X 4) are contained in a modified hot water tank, and rest on a cone-shaped, cast-refractory hearth. The recycled vessel is airtight . . . except for a spring-loaded and sealed fill lid, a capped lighting aperture, and an inlet port (the last is simply a two-inch brass swing check valve, which allows the "draw" created by the engine to pull controlled amounts of air into the firebox).

Incoming "atmosphere" is directed through a series of holes drilled into one shoulder of a discarded wheel rim (which is girdled with a circular band of strap metal and fastened to the bottom of the tank), and supports combustion in the vicinity of the hearth. As the fuel in that area burns, it consumes the oxygen in the air—creating carbon dioxide and water vapor—and forms a bed of glowing charcoal, which collects on a grate sus pended from chains several inches below the hearth assembly. (Simultaneously, a heat-induced "decomposition" zone is created right above the combustion region . . . driving gases from, and carbonizing, the wood prior to its incineration.)

The mixture of CO2 and moisture—in addition to some creosote—is then drawn through a "choker" (positioned between the hearth and the charcoal grate) and forced into the embers at the lower part of the tank before leaving the gasifier. The choke serves as an air restricter which blends the various vapors and directs them through the glowing coals, where they're reduced to the combustible gases carbon monoxide, hydrogen, and—in small amounts—methane. The final product also contains a good deal of nitrogen, along with some unconverted CO 2 and traces of tar and ash.