A Wood Gas Powered Lawn Mower

When mowing the lawn, you generally have a choice of pushing power, electric or gasoline. Thanks to the nutty inventor [Colin Furze], you can now add wood gas to the list, as long as you don’t mind some inconvenience. He built a wood gas generator on top of a formerly gasoline powered lawn mower, so he can now run his lawn mower on wood chips.

Wood gas generators have been used with internal combustion engines for a very long time, reaching their peak in the later parts of WW2 when fuel shortages plagued Europe. When wood is burned at high temperature but with limited oxygen, it produces a combustible gas mix that can be fed into an internal combustion engine. [Colin]’s generator went through a number of iterations, and the problem-solving that goes into a project like this is always interesting to watch. We would not recommend running tests like these indoors, but we suppose no [Colin Furze] video would be complete without a bit of danger.

On his first version he had an extraction fan that was too close to the outlet of the burn chamber, so it melted very quickly. The combustion temperature was also not high enough, which required some changes to the chamber geometry. The main problem that plagued the project was filtering out the moisture and tar. [Colin] did eventually get the lawn mower to run on wood gas, but tar was still getting into the engine, which prevented it from starting the second time. The filtering system will need some refinement, which [Colin] will address in his next video, which he also hints will involve some sort of diabolical swing set.

How [Colin] has escaped serious injury up to this point is beyond us, but his projects have undeniable entertainment value, ranging from a giant hydraulic exoskeleton, to a hoverbike. We’ve also seen a number of other wood gas projects, including a wood gas powered bicycle, and gasometer storage tank.

44 thoughts on “A Wood Gas Powered Lawn Mower

  1. Needs to run on grass clippings. Need a snowblower that runs on snow too. My burn barrel runs on junk mail, made it from the outside of an old washing machine. I go to the backyard to “wash” the papers. It’s totaly redneck/ghetto, but it wash & dries in 1 cycle.

    1. Yeah I was thinking of running it on grass clippings too, but would there be enough? But your comment about junk mail, that’s inspired, a wood gas generator that runs on junk mail, made mostly from pulped wood, and you have a never ending supply of fuel, genius!

    2. I can’t watch the video where I am but I gotta know, is that thing self propelled? if so I love it, maybe a convert a rider or zero turn…add a little guidance … watch it mow the lawn on the pile of sawdust near the woodpile … where’d I put that 23 HP Kohler …

    3. You “warsh” the papers hopefully there are no plastics. I remember when every house had a burn barrel at the alley, and there were no plastics. I get about a garbage (thirty gallon) can of junk mail a year. I saved it once to one of those metal cans that the city no longer picks up, it got recycled.

      1. Tar has always been a problem in gasifier systems. This is true in both wood gasifiers for vehicles, and for coal gasifier plants for lighting/city gas.
        Tar isn’t watery, it’s the heavy hydrocarbon fraction.
        The solution is to bubble the gas through cool water tanks to make sure it all condensates and ends up in the water, and then filter it through wood shavings/chips to catch the last bit of heavy hydrocarbons.

      2. Cats aren’t necessarily a deal breaker. Provided you can do something clever with Nickel or Copper rather than Rhodium or Palladium, well unless you can throw megabucks at development. Copper shows heavy hydrocarbon reforming potential, think you have to get it over 85 C though.

        1. Yeah lots of metals work well for catalysing carbon chain reactions the reason the expensive fancy stuff goes into vehicle cat’s is that they are entirely passive systems that have to work quite rapidly and only off exhaust temp to start with (then temperature they can generate from doing their job).

          So processing that tar in the Colin bunker is quite possible.. Could even just distil off the lighter stuff and use it for the post apocalypse lubrication. And burn the heavy stuff in a marine fuel oil diesel engine… Should be about right for them.

  2. Forget woodgas compressed air is the way to go.
    High power density, conversion efficiency and virtually unlimited storage lifetime. Cyclonic heat separation for water and warm / cold air, Tesla turbines to generate electricity, venturi effect vacuums. Cars, trucks, lawnmowers. Repurpose the existing propane gas network to carry air. Even freeze distille the atmosphere and rebalance the gas percentages.

        1. Compressing air produces a LOT of waste heat. You lose a few dozen of % in the compressor. It is very inefficient.
          For any serious amount of stored energy, you will also have to work with several hundred bar, which carries enormous risks.
          Compressed air has been used in ‘flameless locomotives’ for the mining industry because you don’t want electric sparks or a boiler fire in a mine, but those fireless locomotives had to be refilled with air every 15 minutes or so.
          It has also been used in a tramway in france i think. It was moderately succesful but electricity soon surpassed it.

          1. In terms of compressor losses, this is dependent on how much the air gets to heat up in the compressor chamber. The increase in heat is just due to the thermal energy in the air getting denser due to one compressing the air. And this increase in heat causes additional pressure for one to fight.

            If one allows this additional heat to dissipate into the cylinder walls, then it won’t be able to reach as high temperatures, and thereby not add as much pressure. To give the air as good of a chance as possible to do this, we preferably want a fairly small diameter to our cylinder, and also run it at a low RPMs. (Our efficiency is eventually mainly limited by friction and other mechanical losses.)

            Most shop compressors you can find in most stores and industrial suppliers aren’t aiming at efficiency, but just pure throughput. So they aren’t a remotely good example of how efficient compressed air energy storage is. (And yes, most shop compressors are having rather poor efficiency.)

            This all means that the power density of compressed air energy storage isn’t all that impressive if one aims at efficiency. And most flameless locomotives aimed at producing a lot of power, efficiency weren’t a remote priority. (mainly due to how cheap it is to produce compressed air.)

      1. Not really every thing CRJEEA says is largely true. Though I’d not call it relevant here – you will always need something to compress the air with – so a woodgas powered engine could be the best choice for your location. Solar PV, water, wind, muscle lots of options out there depending on your needs – but plant waste that will gasify is pretty common.

        The one real crux against compressed air is the power/power-density to efficiency you can only really have one – either the system is quite large but very efficient or its focused on peak power/ small volume in which case efficiency of compressed air is pretty low. I still like compressed air for many tasks.. Not sure ‘cordless’ lawnmowing would be one though – that seems like a run the airline to it for efficiency.

    1. Domestic gas lines operate at about 20mbar (in the UK), that’s about 0.3psi, so I’m not sure it would be that useful in a domestic setting.
      I don’t know if anyone has tried estimating the energy losses in using compresses gas to transfer energy, but electricity transmission from power plants to homes has losses of between 6% and 10%, so you’d need to improve on that (and by a long way if you wanted people to switch).
      I’m not sure what the point of a Tesla turbine is in this case, they’re less efficient than a standard bladed turbine, and their only advantage (they can deal with grit etc. that would chew up bladed turbines) isn’t any use when you’re dealing with compressed air.

      Where compressed air/gas does have a use is in short to medium term energy storage.

      1. The gas pressure in houses and in the local area is as you say typically using fairly modest pressures. Mainly since the flow won’t be gigantic. (Though, as one moves up the supply line, one eventually finds a pressure regulator supplying gas from a pipe with a fair bit higher pressure.)

        Supplying power via compressed air on the other hand is likely not a too poor solution and is a thing. But mainly in industry where the air can be used to power tools directly.

        But I doubt that compressed air is a good medium for power transmission over longer distances. (And if we think of it, we can use a wire as thick as a strand of hair to send over a kW of power without major losses, can’t really do the same with air….)

        I can see a limited use of it in terms of energy storage, where we use underground pipelines as the storage vessel for the air, and have smaller distributed decompression facilities. Since it can give an extra level of redundancy to those in need of more uninterruptible power, like hospitals. (and data centers, industry, and society at large.)

        For an example. A 50 cm ID glass composite pipe would only need a wall thickness of 32 mm (safety factor of 4) to handle 120 bar, and would thereby store 11.28 MJ per meter, or 3.13 kWh/m.

        And being able to step in on a more local scale in the power distribution system during peak hours to ease of the burden from the grid itself can increase overall power efficiency. Transformers have core losses that are rather constant regardless of how little one uses the actual grid. Larger transformers = larger losses. By supplying extra power locally during peak hours, we can effectively have smaller transformers and have lower losses during low hours too.

        Or substations can have two more more transformers in parallel, and just disconnect a couple of them when they know there isn’t going to be a large load on the grid. Switching them back in is likely going to be tricky, but its rather rare that power demand spikes out of the blue. And when it does, there is usually a blackout regardless…. And this is honestly where local power storage would be beneficial.

        Also, in regards to Tesla turbines, they have another advantage over bladed turbines too. The very simple design of a Tesla turbine means that it is rather easy to build and balance, and thereby it is easier to achieve higher RPMs without the need for fancy gears. But efficiency is as you say, not its strong side….

    1. It’s referring to the power used to turn the blades, not move the mower forward. Old lawn mowers, the blades were powered by pushing the mower forward and turning the wheels.

    2. I read it as the cutting action is driven by one of the following:
      -Human push

      At the same time, the propulsion of the mower could come from human push, electrical, or gasoline. I think I’m in the same boat having not seen an electric mower with electric propulsion; not to say it couldn’t be done.

      I have a (human powered) push reel mower so I can trim the lawn late at night or early in the morning without bothering the neighbors (or wife, or baby).

  3. He doesnt get hurt because of his safety tie! But for real, he did get hurt at least once when he burned his arm when testing a turbine engine iirc. Anyway this project is awesome as usual, cant wait for his next video!

    1. Yeah, we actually posted about the burnt-arm video, even though it was on the edge of a) gross and b) exploiting YouTuber pain for gain.

      But given all the quasi-dangerous stuff that Colin does, we thought it made sense to post the downside too.

      All in all, though, he does appear to at least know where the danger lies, which is IMO the first step.

    1. In ‘serious’ gasifiers, it is indeed bubbled through water. This cools the gas and makes any too heavy HC’s condensate. And it produces tons of highly polluted waste water.
      Bubbling through oil is not useful for gas for driving engines. It was used for gas lighting, though. Heavier oil could be added to the gas mixture to increase the brightness of gas flames in the time before glowing mantles became a thing.

    2. I’d be interested in seeing how well it did bubbled through kerosene. Now kero vapor would be low octane, but there’s high octane components of the wood gas, and mower motors are not very high compression.

      However, it’s all dependent on how the gasifier is set up and what exactly it’s outputting. Also depends on whether it makes for “ridiculous” kero consumption or not and local price and availability. Hereabouts the only easy supply is the gallon jugs from hardware stores which are stupid expensive at $10 or so. I think it could be got in bulk a few hundred gallons at a time for around heating fuel prices though. Decades ago, you used to be able to buy it from a pump like gasoline, but haven’t seen one in forever.

  4. Kudos to the builder of a wood chip powered lawnmower! It’s a lot easier to attach a 20lb propane tank, people throw them out all the time with their grill. Smells like a forklift running, made mowing the lawn fun. Those were the old days….I converted my backyard to 100% garden, sadly it’s now a weed garden

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