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Everything Old Is New Again: Biomass Burners at Automechanika Frankfurt

The charcoal-fueled Opel Kapitän. Click to enlarge.

by Jack Rosebro

Visitors to one of the 4,500 exhibits at last week’s Automechanika Frankfurt 2006, which is Europe’s largest and best-known automotive service, repair, and aftermarket accessory trade show, were treated to a biomass “blast from the past” in the form of a 1938 6-cylinder, 3.5-liter Opel Kapitän which ran on wood and charcoal almost seventy years ago.

Charcoal burning conversion kits, which are really wood gas generators, enjoyed a brief civilian and military niche market in England, Germany, Australia, the United States, and other countries up to and during World War II. Wood gas generators were used to power taxis in Korea as late as 1970.

A charcoal burner actually burns the gases produced by heated wood. The burner is a two part system: a closed chamber with chunks of wood in it, and a charcoal burner to heat the closed chamber and make the wood generate gases by a process called pyrolysis.

Flammable gases produced by pyrolysis are then routed to a carburetor of sorts, mixed with air, and burned in the engine’s combustion chambers. Once the wood in the closed chamber has produced gases and turned to charcoal, it is transferred to the charcoal burner to heat the next load of wood. Some charcoal-fueled cars were designed to be started on gasoline, and would then be switched to charcoal once the vehicle was underway.

The vehicle was part of a display entitled “Alternative Kraftstoffe und Hybridantreibe” (Alternative Vehicles and Hybrid Powertrains) by Deutsche Kraftfahrzeuggewerbe, a German organization that was at the show to promote uniform teaching standards related to alternative fuels and hybrid powertrains.

The sleek CLEVER. Click to enlarge.

The dark green Opel was nestled among displays of current alternative fuel technologies, including VW’s CNG-fueled version of its Caddy minivan (earlier post), a bioethanol-fueled Ford Focus, a BMW-powered, CNG-fueled CLEVER trike (earlier post), a hydrogen fuel cell-powered Opel minivan, a Honda Civic hybrid powerplant, and an engine equipped with Valeo’s integrated starter-alternator (earlier post).

Fuel economy for the biomass-fueled relic was 100 kilometers for every 38 kilograms of charcoal.

In February, University of Hawai’i researchers announced the successful construction of a working alkaline fuel cell powered by charcoal.


  • Automechanika Frankfurt website

  • Deutsche Kraftfahrzeuggewerbe website

  • University of Hawai’i research on charcoal-fueled fuel cells



I think the fuel economy was roughly equivalent to 8 mpg. Hopefully there was a forest to pull into when the tank was low. This display ties in with German BTL producers lobbying for a tax break.

Joe Rocker

Good luck trying to pass emissions with that.


From the angle in the photo, that Opel looks like a fairly handsome car. Underneath that charcoal burning apparatus, of course. I had thought such setups were only used during WWII to cope with the petroleum shortage, not before.

Jack Rosebro

"Good luck trying to pass emissions with that."

You're right! A typical 1930s gasoline-fueled vehicle in good running condition would probably put out around 5% carbon monoxide, while a wood-gas generator produced about 20% carbon monoxide. By comparison, today's vehicles produce less than 0.005% carbon monoxide at idle.

"I had thought such setups were only used during WWII to cope with the petroleum shortage, not before."

World War II certainly represented the zenith of wood-gas burning vehicles; almost all of Denmark's vehicles and 40% of Sweden's automobiles ran on wood during that time. However, the technology has been around since the 1880s.


My grandad drove a wood powered truck during the depression when they couldnt afford gas.


The back of the Opel reminds me of Mr. Fusion in Back to the Future. Now if we had some of those, we could be all set! :-))

Alan Belson

I'm afraid we have been treated to typical media inaccuracies by whoever wrote this up. What you see on the back of the Opel is a version of an 'Imbert Gazogene' or down-draft wood gasifier. It used dry wood chunks about 2" [5cm] cubes @ 15%-20% MC as the fuel, [ in the sack ], loaded into the hopper, lid shown open. The 'Gazogene' has a zone of hot charcoals, [c.800-1000C], at its heart which is fed with insufficient air for full combustion. The engine sucks air through the 'Gazogene' from the inlet-manifold's depression, which thus produces gas more or less on demand. In that 'charcoal reactor' almost all the products of pyrolysis, like steam, tars and acids, are [theoetically at least] converted into hydrogen and carbon monoxide to create a gaseous fuel, usually c.20% carbon monoxide, c.20% hydrogen, c.50% nitrogen, plus methane, water vapor and carbon dioxide. As the charcoal is consumed, the wood chunks, from the hopper above, fall to replace it. Fine gas-borne ash is partially removed by a cyclone, the cylindrical device at the extreme rear of the car. There was usually another ash-filter, probably mounted in the front compartment of the Opel, of a drum of granulated cork or oiled wood-chips. I assume this is a rear-engined vehicle, [see the rear louvres], indicating another [unseen] pipe to bring the gas back to the inlet manifold. The pipe carrying the gas over the roof is the primary gas cooler for better volumetric efficiency. There may even be a gas-cooling radiator up front, this was commonly fitted. 'Producer', or 'blue gas' has a low calorific value compared to say propane, but it burns well in most types of engines. Compression ratios of up to 14:1 are possible and diesel engines can be modified to run on it.
As to emissions, an 'Imbert' fueller would have produced exactly the same or better emissions as a contemporary gasoline-fuelled vehicle of the time, and the fuel consumption, counted in dollars, would be cheaper than gasoline today, with 1940's quoted consumptions of around 60 miles on an 80lb fill of wood. These devices were mostly abandoned after WWII as low oil prices made them uneconomic. They were also prone to poison the owner with carbon monoxide leaks [!] or explode if mis-treated on light-up and were dirty and fussy to operate with often variable performance. The gas could also cause excessive engine wear if too much ash was fed with it through the engine.


Jack Rosebro

"I'm afraid we have been treated to typical media inaccuracies by whoever wrote this up."

Other than what is noted below, I really don't see any contradictions. But thanks for reading.

"I assume this is a rear-engined vehicle, [see the rear louvres], indicating another [unseen] pipe to bring the gas back to the inlet manifold."

Nope. Engine's in the front. I checked.

"As to emissions, an 'Imbert' fueller would have produced exactly the same or better emissions as a contemporary gasoline-fuelled vehicle of the time"

No. Even a 1930s vehicle in good running condition does not produce 25% CO. If It did, the excess gasoline would wash the cylinder walls of lubrication. Expect to see 2 to 6% CO on a well-tuned vehicle from the 1930s. I have measured them.

J Perry

is anyone running on wood gas in the USA and if so pleasew let me know ?

Cheryl Ho

There are developments in DME in China today:
DME is an LPG-like synthetic fuel can be produced through gasification of Biomass. The synthetic gas is then catalyzed to produce DME. A gas under normal pressure and temperature, DME can be compressed into a liquid and used as an alternative to diesel. Its low emissions make it relatively environmentally friendly. In fact, Shandong University completed Pilot plant in Jinan and will be sharing their experience at upcoming North Asia DME / Methanol conference in Beijing, 27-28 June 2007, St Regis Hotel. The conference covers key areas which include:

DME productivity can be much higher especially if
country energy policies makes an effort comparable to
that invested in increasing supply.
National Development Reform Commission NDRC
Ministry of Energy for Mongolia

Production of DME/ Methanol through biomass
gasification could potentially be commercialized
Shandong University completed Pilot plant in Jinan and
will be sharing their experience.

Advances in conversion technologies are readily
available and offer exciting potential of DME as a
chemical feedstock
By: Kogas, Lurgi and Haldor Topsoe

Available project finance supports the investments
that DME/ Methanol can play a large energy supply role
By: International Finance Corporation

For more information:


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Carl Talley

My friend built a coal fired gas generator for himself and his wife during ww2 and they got 600 miles to 100 lbs of coal. By the way he has a PHD in engineering and a PHD in chemistry. My 88 year old friend is going to give me his drawings so i can reproduce his mechanism. The carbon monoxide produced is the main heat source, but all the other gases are flammable too. The main reason for wear is the lousy oil that was available at the time and poor metallurgy also poor machining. Some of these engines lasted 10 years or more. This from someone who was there and qualified to speak on the subject. I will let you know what the results are when I finish building ours.


Brendo D Buenaluz

When I was about 8 yrs old, in Manila, Philippines - during the Japanese occupation, I have seen cars moving in the street of the city which are charcoal fed. Seems like this technology has been around for sometime.

Why is combustion not more complete and why can't an oxidization catalyst take care of producer gas engine emissions? Are there any published test results with a catalyst engine?


Hi: I arrived in Europe in 1945 with the US Merchant Marine. Most autos with the exception of US Military vehicles were powered by charcoal burners mounted on the rear of the car. True, these charcoal burners were quite large because they were home-made and very primitive. However, if modern technology were incorporated into the design and efficiency of the units, I beleive they could be much smaller and more efficient than the home-made units used by the Germans during WW2. Many of these units were still in use when I arrived in Germany in early 1951 with the US Army. This was because of the high cost and shortage of gssoline, and the depressed ecconomy of the Germans.
Thanks: Bud Maresko

Will M

As regards a wood/charcoal/coal burners, I have not had any experience with such. However, I have seen coal fed industrial units installed shortly after WW1 and was used to run a large slow running engine driving a generator and air compressor. This engine had 15 ft flywheels.
A large tank about 15 ft in diameter and about 10 ft high acted as the gas generator. It had a revolving tray underneath the tank in which the ash was allowed to spill. The green coal was introduced by a star feeder at the top and was regulated by the engine throttle and adjusted by the operator. A fire was started in the ash pan and as green coal was introduced on top of the fire the gasses were drawn off by the engine which was electrically spun until enough coalgas was produced and drawn off to run the engine.
The coal hot bed go fresh air thru the ash bed to an incadecent bed which was continually being used up to heat the green coal.
What type of filtering the gas had I sumise came from filtering up thru the green coal bed.
In the 1980's there was some interest in wood burning units installed in pickups.
If any one has ideas or plans for wood or coal for auto transportation, please e-mail me.


coal ran cars would be very popular here, but the oil and gas companys would not like that as they are the energy Czars of the USA. Also I would convert my home to run on coal again back east for heat with home heating oil at record high prices near 5 bucks a gallon!

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