Save Gas: Use Producer Gas from Wood!

Running an engine on wood is not for everyone. But it may be just the fuel you're looking for in order to save gasoline consumption for your car, truck, generator, or farm machinery.

Imagine adding a bag of wood chips to the hopper of your producer gas generator, opening a door on the combustion chamber, starting a small fire, finishing your morning coffee and three or four minutes later taking off down the road. It's been done!

Millions of cars, trucks, tractors, and taxis were operated this way during the worldwide petroleum shortages of the late 1930's and into the 1940's. Both Volvo and Ford build production model vehicles during those years, with the apparatus built into the design of the vehicle. Charcoal-burning taxis were still common in Korea as late as 1970.¹

What is Producer Gas?

Producer gas is a vapor by-product, primarily carbon monoxide, of a high-temperature combustion process (1800 degrees Fahrenheit), obtained by restricting the amount of air supplied to the burning fuel. Other names for it are fuel gas, water gas, and town gas.

The only requirement is that the fuel must be carbon-based--wood, charcoal made from wood (grilling charcoal is vegetable-oil based and will not work), coal, peat, rice hulls, etc.

What about Emissions?

A producer gas generator with enough capacity to operate a vehicle for several hours will only create a few tablespoons of ash.

Paper, oil, or water filters trap any tar and ash that may come through the system.

An engine running on producer gas has only two exhaust emissions coming out of the tailpipe: carbon dioxide (not a "greenhouse gas") and distilled water! According to the author of the internet article "Wood Fires that Fit, "as long as wood burning is sustainable and doesn't cause deforestation, its CO2 emissions are neutral -- the CO2 released in the fire simply gets recycled back into more trees."²

How Does a Producer Gas Generator Work?

Here is a very simplified description of the process:

Once the fuel begins to burn at approximately 1800 degrees Fahrenheit a chemical process takes place called pyrolysis. These high temperatures are reached by simply restricting the airflow to the area of combustion. The by-product of this pyrolysis is not the sooty smoke you see spiraling up your chimney from a fireplace, but primarily carbon monoxide gas in vapor form. This carbon monoxide gas is the "producer gas".

First this gas is cooled to reduce volume and increase horsepower potential. Next it is cleaned in a filter or scrubber. At that point the producer gas is ready to be mixed in an approximate ratio of 1:1 with outside air and drawn into the intake manifold of an internal combustion engine. No other holding tank or pump is needed. The vacuum created by the displacement of the engine cylinders adequately pulls in the correct amount of gas/air mixture as determined by the throttle and load demand.

How does Wood Compare to Gasoline?

In general, the amount of energy in one cord of wood equals that of 100 gallons of gas. A cord of wood is a volume measurement, generally considered to be three stacks cut and split to 16-inch lengths, each 4' high by 8' long (4' x 4' x 8').

Here's another way to compare: Your 1986 Chevy C10 pick-up holds 25 gallons of gas, and you are able to drive 400 miles at 60 miles an hour on each fill-up. Four tankfuls (100 gallons total) would give you a driving range of 1,600 miles.

The equivalent amount of energy in one cord of wood, operating the same engine in the same truck, would be able to take you 1,600 miles also, and probably as far as 2,000 miles or more.

A cord of wood also equals about 128 cubic feet, and weighs about 2,000 lbs. Quality charcoal made from wood has a ratio of about 1:10 by volume and weight. In other words, a cord of wood will produce about 13 cubic feet, or 200 lbs., of quality charcoal. The amount of energy potential is not reduced, when the wood is first converted to charcoal, because the charcoal is nearly pure carbon.

How Practical is it?

I ran across a story set in the World War II days of gasoline shortages, of a Navy pilot in Australia who was called up to active service. He tells of his experience driving the 200 miles from his home to the Navy base, in a full-size Buick with a 350 cubic-inch V-8 engine equipped with a charcoal-fired producer gas generator. He filled the hopper when he left with one 50-lb. bag of charcoal and added two more bags along the way, averaging 80 miles an hour!

Another anecdote tells in detail of a couple in the 1980's who drove the circumference of Australia on wood they picked up along the way. If wood was not plentiful they used sugar cane cuttings and anything else they could find that would burn. Their story may be found at: http://members.tripod.com/~highforest/woodgas/woodfired.html.

The Federal Emergency Management Agency released a report in 1989 detailing how to build a producer gas unit from readily available supplies, which would adequately run a tractor, generator, well pump, etc.³ I have used their drawings to build a successful prototype, which I hope to improve upon in order to begin generating electricity, followed by the application of what I learn to operating a vehicle on producer gas.

Will we see cars by the thousands efficiently buzzing around town, running on only wood in the near future? Probably not, for a variety of reasons. But the application of this simple, proven method may be perfect for your needs and abilities.

Pitfalls to Producer Gas

OK, so what are the drawbacks? There are several:

1. Wood must be reduced in size to be compatible with your unit, which takes some work. The family in Australia could use anything shorter than 8 inches and about 2 inches in diameter. The Gengas version in the FEMA report required smaller wood chips, which any typical wood chipper could create from limbs and branches. If charcoal is used, there is of course some labor and handling involved, but it's not too difficult to make large quantities of charcoal at a time.

2. Some maintenance is involved. Filters must be cleaned daily, and periodic maintenance of the engine is required. Anyone with beginning auto mechanic skills could handle most of the maintenance readily. Carburetion could be as simple or as complicated as you like.

3. Driving habits may have to be modified, depending on your vehicle, the load, and road conditions. Typically an engine will have about a 40% reduction in horsepower compared with gasoline, but this can be limited to 20% or less with the addition of a turbocharger and different rear end gear ratios. The introduction of water into the intake air of the producer gas generator can increase horsepower potential by as much as another 10 to 30%, since the hydrogen breaks apart from the oxygen at the temperatures needed for pyrolysis, and hydrogen adds to the effectiveness of the producer gas mixture.

Do some reading and experiment! If you have already, I would be interested in hearing about your experience, whether positive or not.

References:

^1. LaFontaine, H. "Construction of a Simplified Wood Gas Generator for Fueling Internal Combustion Engines in a Petroleum emergency." Internet. Database available online. http://www.gengas.nu/byggbes/executive_summary.shtml

^2. "Wood Fires that Fit." Internet. Database available online. http://journeytoforever.org/at_woodfire.html

^3. LaFontaine, ibid.

Resources:

http://www.gengas.nu/byggbes/index.shtml FEMA Report, with plans and drawings.

Cash, John D. and Cash, Marin G., Producer Gas for Motor Vehicles, 2^nd ed., Sydney: Angus and Robertson, Ltd., 1942 (reprinted by Lindsay Publications, Inc., 1997)

http://journeytoforever.org/at_woodfire.html Excellent source.