Can We Use Wood to Beat the Gasoline Shortage?

Hardwood chips are now driving the first solid-fuel trucks to appear on American highways.

| May/June 1974

Hardwood chips are now driving the first solid-fuel trucks to appear on American highways. The standard gasoline motors of these trucks have been converted to the use of producer gas, a mixture composed of hydrogen, methane, carbon monoxide, carbon dioxide and various tar gases. Pictured in the image gallery is an experimental conversion made by the Rheingold Brewery of New York City, and believed to be among the first efforts in this country to adapt producer gas for use in commercial vehicles.

Under ordinary driving conditions, wood is added to the gas producer every 50 to 60 miles. Hardwood, cut into chips less than 4 inches in length to prevent arching or pocketing in the generator, is used in preference to softwood such as pine because it leaves fewer tars and gummy residues. Even so, the cooling tanks and filters on the vehicle must be cleaned every 900 miles, and motor overhauls are in order every 5,000 to 8,000 miles.

Technical studies indicate that about 1.76 lb. of wood are required per horsepower hour. Gas producers fueled by coal or coke are more efficient, but they are much larger and more complicated. With wood, if no major changes are made in converting the engine, the maximum horsepower is about 70 percent of that on gasoline, provided that the spark is advanced and the fire is properly managed. But if the compression ratio of the motor is increased (producer gas knocks less readily than gasoline), horsepower can be pushed up to 85 or 90 percent of the gasoline rating. In general, tests show that substantially more gear-shifting is needed with producer gas.

When a cold start is to be made, wood is added from the top of the hopper and an electric fan is attached to the gas offtake pipe so as to suck a current of air through the producer. Ten minutes after the wood is lighted, the generator manufactures enough gas to run the truck. Starting the engine on gasoline will create sufficient suction to build up the fire, but this takes much longer.

As shown in the schematic drawing, the gas producer is a downdraft type. Air is supplied to the fire — within the conical walls of the refractory, or gas-generating area — by five air nozzles which run through the firebrick from the outer air jacket. The gas, produced by partial combustion of the fuel, flows out the offtake pipe to four cleaning and cooling tanks, fitted with baffles and connected in series. As it is cooled the gas becomes denser (under Boyle's law) and hence more Btu's are supplied to the motor at each intake stroke.

A condensation trap is provided at the end of the fourth cooling tank to catch any moisture deposited by the gas, which next passes through a steel-wool filter and oil bath in a tank on the running board. Just before the gas pipe reaches the intake manifold, a valve admits air to the gas, at about a one-to-one ratio, and the mixture is then fed past the throttle to the motor.

9/6/2009 9:38:13 PM

Farm boy. Even in forests grown for lumber there are many small trees that must be cut down to let the others grow bigger. Popular Science says we could us that for celulosic Ethenol. Burning dead wood doesnt effect tree huggers. Wood is CO2 neutral because the tree is just releasing the CO2 it stored. 25 mile per hour is not acceptable since we dont use horses anymore. I burn waste veg oil in my 1984 Mercedes 300D turbo diesel. The exhaust is carbon neutral and the emmisions are 67% less.

12/27/2008 12:31:58 AM

We manufacture a "tar free" gas producer

9/20/2008 4:18:49 PM

I've been looking at wood-gas for a long time.It works well and i don't care about the exaust emission's___beat's walking. I think it will be cleaner used as power for a generater myself. Keep up the good work. later

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