By on July 10, 2014


The autoblogosphere is abuzz with the topic of “rolling coal“, apparently the practice of some diesel pickup truck enthusiasts who fiddle with their fuel systems so as to produce voluminous clouds of dense black, sooty exhaust smoke. I have to admit that when I first saw the phrase “rolling coal” in a headline at Jalopnik I thought it had something to do coal gasification and running cars on wood gas or syngas. After finding out that rolling coal wasn’t what I thought it was, I did look into the history of powering motor vehicles on wood gas and ended up finding out about these rather odd looking cars and trucks known as gas bag vehicles. Frankly they’re more interesting to me than whether or not pickup truck driving bros are blowing smoke in the faces of Prius drivers. I believe that you’ll find these vehicles interesting as well.


The process of using oxygen starved combustion to turn organic material into a combustible gas has been known for 175 years. Gustav Bischof built the first wood gasifier in 1839. By the turn of the 20th century, before the use of natural gas started proliferating in the 1930s, in many municipalities syngas produced from coal was centrally produced and distributed via pipelines to homes and businesses to use for heating and cooking. In 1901, Thomas Parker made the first vehicle powered by wood gas.


The best known use of wood gas and syngas to power vehicles, however, was in Germany during World War II.


Germany was heavily dependent on petroleum mined outside of the country’s borders so gasoline and diesel fuel were rationed for the civilian population in order to reserve those fuels for military use. Germany may have had little petroleum but it had a lot of domestic coal.


Considerable effort was also put into industrial scale production of synthetic fuels and lubricants using the the Fischer-Tropsch method. It’s estimated that 9% of the Reich’s liquid fuel and a quarter of the automotive fuels used during the war were synthetics made from coal.


In addition to commercial scale synthetic fuel production, by the end of the war there were about a half million German cars, trucks, buses, tractors, motorcycles, and even marine ships and railroad locomotives that were equipped with portable wood gasifiers. Wood gas powered vehicles were also common elsewhere in wartime Europe.


The widespread use of synthetic gas to run cars and trucks dates to another war, though, World War One. As mentioned, many cities distributed what was known as “town gas” or “street gas”, a byproduct of making coal into the cokes that are used to refine iron.


During the first world war, some creative folks in France, the Netherlands, Germany and the United Kingdom figured out that they could run their motor vehicles, like Thomas Parker did, on that gaseous fuel rather than on gasoline, which was in short supply due to the ongoing hostilities.


One of the barriers facing modern day gaseous fueled vehicles is that compressed natural gas (CNG) or liquified petroleum gas (LPG) have lower energy densities than gasoline so the tanks for the compressed gas end up being about twice the size of a conventional liquid fuel tank. “Town gas” has an even lower energy density than CNG or LPG. At normal atmospheric pressure, the town gas equivalent to a liter of gasoline takes up between two and three cubic meters of volume.


While today CNG vehicle operators can buy commercial and even home gas compressors, a century ago such compressors weren’t readily available. Also, syngas is made up of carbon monoxide and hydrogen. Though it was possible to compress town gas, it wasn’t practical. Carbon monoxide breaks down when compressed and the steel tanks of the day could not contain hydrogen gas without leaking.


The solution was to store the syngas in large inflatable bags, essentially balloons, made of coated fabric, that were mounted on the roofs of the vehicles. It was obviously more practical for larger vehicles, like trucks and buses, but some automobile owners made the conversion as well. Some of the commercial conversions included fairings and bodywork to hide the bags and provide some aerodynamic improvement (back then it would have been called “streamlining”), and a place for advertising, but in most cases the vehicles looked like they were hauling around bales of cotton, well, until the bags deflated as the gas was consumed. Some owners built metal or wooden frameworks to contain and protect the fuel bladders, which were made of rubber coated silk or other fabric material. If they sprung a leak, they were repaired with a patch for a bicycle tire tube.


Because of the lack of energy density, gas bag vehicles were strictly for short range driving. With consumption of 13 liters of gas per kilometer, the equivalent of 22 mpg with gasoline, a 13 cubic meter gas bag would give a range of about 50 km (~30 miles). It’s possible that some drivers fitted some kind of fuel gauge, but apparently most just watched their fuel tank deflate. The vehicles could be refueled wherever town gas was supplied.


The main drawbacks to the gas bag vehicles were fire risk, bridges and the fact that your fuel tank might blow away if you went too fast. Passengers waiting at bus stops were warned not to smoke.


“Rauchen verboten” – smoking was forbidden at bus stops due to fire risk from gas bag leaks.

Drivers had to plan for overpasses and other potential overhead obstacles and were urged not to exceed 30 mph, both to preserve range and to keep the gas bag secured to the vehicle. Sidewinds were also a problem.


Despite their drawbacks, gas bag vehicles’ use has not been restricted to wartime. Because the fuel is an inexpensive byproduct of industrial processes the city of Chongqing, China developed gas bag buses as a cost effective public transportation solution in the 1960s and gas bag buses stayed in operation in China into the 1990s.


Ronnie Schreiber edits Cars In Depth, a realistic perspective on cars & car culture and the original 3D car site. If you found this post worthwhile, you can get a parallax view at Cars In Depth. If the 3D thing freaks you out, don’t worry, all the photo and video players in use at the site have mono options. Thanks for reading – RJS

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20 Comments on “Rolling [Gasified] Coal: Gas Bag Vehicles...”

  • avatar

    Great article – I did not know of this use of (what we called in the steel industry) “Coke Oven Gas”.

    South of Pittsburgh, the Clairton Coke Works processed coal into coke, and the COG byproduct was captured and pumped through 2 24″ diameter pipes to all the USS mills along the Monongahela River. It was burned for various low-BTU purposes, (preheating ladles and furnaces after brick re-lining, low-output steam boilers, other uses); it was a nasty-smelling, toxic gas that carried a lot of contaminants that made the combustion byproducts corrosive.

    I can imagine what cities that had these vehicles running around looked/smelled like.

    • 0 avatar

      Great article Ronnie, and very preceptive of you to make the connection. I too have a connection with the coke gas process, but did not know about cars that ran on it.

      >As mentioned, many cities distributed what was known as “town gas” or “street gas”, a byproduct of making coal into the cokes that are used to refine iron.

      >While today CNG vehicle operators can buy commercial and even home gas compressors, a century ago such compressors weren’t readily available. Also, syngas is made up of carbon monoxide and hydrogen. Though it was possible to compress town gas, it wasn’t practical. Carbon monoxide breaks down when compressed and the steel tanks of the day could not contain hydrogen gas without leaking.

      Building on what Shaker said; to get the coke gas into the city mains, the coke plants used massive steam powered compressors housed in large compressor buildings.

      The former Solvay Coke plant in Milwaukee and a coke plant in Seattle were two examples of coke plants that had the huge compressor houses for pumping the gas into the city mains. The Solvay Coke plant was pretty much intact until about a decade ago; as Shaker described, it was a nasty smelling Superfund site full of all kinds contaminants. A developer went broke trying to clear the site to build condos and a marina. Myself and Larry Tucker, another computer geek, tried to rally to have the compressor house with it’s rare steam powered compressors preserved intact. We failed at our efforts, but Larry took a ton of pictures which I posted on the web, and a few of the machines were saved:

      A short-lived TV series called “Urban Explorers: Into the Darkness”; which was about individuals who explore derelict urban sites like these, also came and filmed an episode there. They called me at work when they got to the plant gates to learn more about the building they were about to film in before going in, and mention me in the credits.

      It was decided that the former coke plant site in Seattle was forever too toxic for anyone to live and work on, but was fine for short term visits. So, the plant site was turned into Gasworks Park; it is located on Northlake Way, and is used for concert venues. Fortunately, the compressor house with it’s compressors was preserved more or less intact:

      For those of the B&B who live and visit in Seattle, now you know “the rest of the story” about Gasworks Park.

      Because it was mostly carbon monoxide, coal gas was toxic as well as flammable. A story was told about a man who decided life wasn’t worth living anymore, so he turned on his gas oven, stuck his head inside, and waited to die. But, he did not know that the city had just switched to natural gas, so nothing happened. He then decided that life was worth living after all; took his head out of the oven, and lit a cigeratte to celebrate still being alive…..

      • 0 avatar

        Great photos, thanks for posting the link.

      • 0 avatar

        Nice story except for natural gas and nothing happened.
        During the Depression the suicide rate was high and death by natural gas was a method.

        • 0 avatar

          I think it was more likely by exhaust fumes or coal gas than natural gas.

          There was a home in our town, just a couple of blocks down the church we attend, that had natural gas leaking into their water line due to an underground leak. Apparently, they were aware that they were able to set their tap water on fire, but did nothing about it.

          She was on oxygen, and when she went to light a cigarette one day, her bedroom exploded.

          It could be that you could suffocate due to natural gas; but it is much more likely that it will find an ignition source somewhere and ignite first. There was another home in the region last winter that exploded due to a natural gas leak. JMO.

      • 0 avatar

        jhefner: Nice post.

        The “iron”y is that the coal had to be purified into coke before it could be used as a fuel in blast furnaces to smelt iron, yet the poisonous (flammable) byproducts were deemed acceptable for household use.

        Waste not, want not, I suppose.

  • avatar

    Really interesting. Most people knew about the wood-carburetors in WWII… but i didn’t know about the huge bags. Talk about drag.

    Don’t tell me people were able to use those bags, but today they act like recharging an EV every 100 miles is the biggest problem.

  • avatar

    …i imagine gas bags could be refilled significantly quicker than a modern electric vehicle recharges…

    …ronnie, i presumed the same subject matter when reading the original rolling coal headline as well: thanks for the research and history lesson!..

  • avatar

    Or, you could just go ahead and try to run the car on coal, as GM apparently tried to do with a Cadillac in the 1970s:

    • 0 avatar

      That’s a whole ‘nother concept. I remember seeing a picture of an English car converted to run on steam, supplied by a coal or wood burning stove, during the gas shortages in WWII. I image those cars had far better range, but couldn’t go fast because the tail pipe was a stove pipe chimney.

      I guess we didn’t see much of that here in WWI or WWII because we produced 2/3 of the world’s oil. The civilian rationing of WWII was apparently for PR only. A study of oil shortages in WWII noted none of our military suffered any fuel shortages of any kind at any point in the war, and in fact supplied most of the Royal Navy’s Atlantic fleet as well.

      • 0 avatar

        “A study of oil shortages in WWII noted none of our military suffered any fuel shortages of any kind at any point in the war, and in fact supplied most of the Royal Navy’s Atlantic fleet as well.”

        Standard oil provided also a fuel for German submarines during the war, as described in the article

        • 0 avatar

          Gasoline was rationed as a way to conserve rubber.

          • 0 avatar

            Not that simple. Stocks of gasoline for military purposes were required and rationing was necessary. Natural rubber for tires also. Civilians were not allowed to be living large when a major portion of young men were overseas and casualty lists were long.
            “Wednesday, August 15 1945
            Canned Fruits, Vegetables Off But Meat Stays
            OPA Order Becomes Effective At Once

            Washington, Aug. 15 — (*P)—OPA today announced immediate termination of the rationing of gasoline, canned fruits and vegetables, fuel oil and oil stoves.
            Price Administrator Chester Bowles said that meat, fats and oils, butter, sugar, shoes and tires will stay on the ration list “until military cutbacks and increased production brings civilian supplies more nearly in balance with civilian demand.”
            “Nobody is any happier than the OPA,” Bowles said “that as far as gasoline is concerned, the day is finally here when we can drive our cars wherever we please, when we please, and as much as we please.”

            The Miami News – Jan 2 1946
            Buyer’s Rush Exhausts Tire Supplies Here
            Miamians and tourists waited in lines at auto supply stores early today for tires on the first business day since tire rationing went out with the old year.
            Some of them got tires, but most of them were turned away when meager supplies ran out within a few minutes.
            Some stores had no tires to begin with. Sears … had only truck tires for sale.
            Elbert Gray, assistant manager at Passmore Auto stores … said he sold 54 tires, his entire supply of standard tires within 15 minutes after the store opened …
            Sales in most stores throughout the city were limited to two tires to a customer.

  • avatar

    Ronnie you’ve been putting up some great stuff in the last few days. Keep it coming! Thanks for your hard work.

  • avatar

    “The autoblogosphere is abuzz with the topic of “rolling coal“

    Why does this sound like the 3rd Fox show of the day saying “people are saying” when it’s their own voice they’re echoing?

    • 0 avatar

      Despite my snark above, this is some of my favorite content at TTAC. I love the combination of education and amusement that your well written and (especially) well illustrated articles give me. Thank you. I’m smarter and happier because of your work.

  • avatar
    schmitt trigger

    Ronnie; you are on a roll, Bro! You have written your best blog work in these past few weeks.
    Excellent images, too.

    I have lots of fondness for older industrial plants. My grandfather was a representative for steel making equipment maker Krupps. He would visit mills all over the place.
    When I was a youngster he took me on a visit both to a blast furnace and an electric arc furnace. There are many videos on youtube, but they don’t do justice to the screaming roar and the piercing heat that these furnaces produce when they are operating.

    But to the point of the carbon monoxide: Blast furnace gas in particular contains significant amounts of carbon monoxide. This was burnt and used for several processes within the mill.

  • avatar

    I had never heard of gas bag vehicles before. This is why I love this site, you learn something new nearly every day.

    On a sidenote, one of my co-workers has a woodgas carburetor in his pickup truck. Say what you will, but it’s pretty amazing to actually see a car running with firewood as fuel.

  • avatar

    Very interesting! I didn’t know this existed at all.

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