Introduction To Woodgas

"Woodgas" is the nickname for the gases that can be made by Gasification, from wood, other biomass and waste for heat, power and synthesis of ammonia and fuel (it is also called "producer gas", "synthesis gas" etc.).

One of the worst problem for 2-3 billion people in the world is cooking on wood fires. They cook slowly, the smoke causes glaucoma and lung diseases for the women and children, the children get burned in the fire, and they burn much too much fuel that must be gathered from greater and greater distances. One solution to the world cooking problem is to convert wood and other biomass to gas which can then be burned cleanly in a "WoodGas Stove" with the correct amount of air, some units using a small amount of electricity for a fan (a typical small burner using a single AA cell, lasts 3 hours on high and 6 hours on low).

Wood-gas stoves

Fig 1: Swosthee wood-gas stoves in Malaysia

Wood-gas cooking stoves are perhaps the best answer so far and exceed the performance of any other biomass cooking device. These are gasifiers that produce gas from wood and then burn the gas, leaving ash and charcoal. They're clean, fast and efficient. They burn small pieces of wood, sticks, wood chips, corncobs or nutshells, producing a clean, blue flame and no smoke.

They typically generate 1.5 - 3 KW of heat, comparable to the big element on an electric stove; it burns only 10 g of fuel/min (40% efficient); and it can be used indoors with minimal emissions.A lot of cunning engineering has gone into the development of these stoves, and yet they're easily made from locally available materials -- even tin cans. Technically, they're called "inverted downdraft gasifier" stoves, operating on natural convection.

Fig 2: Richard Boyt's low-tech wood-gas stove, made from 10 tin cans

Gasification is the cleanest, most efficient combustion method known. It has been used for decades where clean heat is required. Examples include the thousands of vehicles which were directly fuelled by Gasifiers during the Second World War, or the coal gas "works" which were common in cities all over the World before natural gas. These produced gas which combusted so clean it was used in chimney-less household appliances such as cookers and heaters, without adverse effects.
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Woodgas Powered Vehicles

Fuel shortages during WWII prompted searches for alternative fuels in England, Germany, Scandinavia and many other countries. One of the most unusual solutions involved the modification of vehicles for use with wood, charcoal, or coal. Typical modifications included A) a gas generator; B) a gas reservoir; and C) carburetor modifications and additional plumbing to convey, filter, and meter the gas into the engine.

The gas generator was an airtight vessel into which was introduced a charge of wood, charcoal, or anthracite coal. Heat was applied to the fuel either internally or externally to initiate a self-sustaining gasification of the fuel in an oxygen deprived environment. The resulting "woodgas" was piped to the reservoir, or in the case of small engines, directly to the engine carburetor. Wood-gas modified vehicles were therefore technically a "dual fuel" vehicle in that a self-sustaining gasification of the wood charcoal, or coal required another fuel to start the process.

Gas reservoir sizes depended upon vehicle, engine, and gasifier size. Small vehicles and engines could be supplied directly from the gasifier, thus eliminating large reservoirs. Larger, more powerful vehicles required separate gas reservoirs to compensate for gasifier outputs which were less than the fuel consumption rate of the engine. These larger reservoirs usually took the form of gas bags that were attached to the roof or rear end of the vehicle. The largest mobile reservoirs were gas bags fitted to busses which were often several feet in diameter and as long as the vehicle. http://www2.whidbey.net/lighthook/woodgas.htm