Woodgas for 70-120 kVa generator

Hi all,

I’m new here and have been reading a lot of interesting projects so far! One topic was about a man that runs a Cummins 6BTA on woodgas, the man is named Patrick Johnson I believe. His installation looks very interesting. I have a 100 kVA generator with a DAF 825 engine. Since gas and diesel prices are insane I start thinking of converting an engine like this more and more… Is it possible and efficient to run a generator dual fuel, and use it for example 100% on diesel when you need it for just a short period, and run it for 80% on woodgas if you need it for half a day or more? That will make it way more flexible for me, and possibly it allows me to run the generator on diesel while starting up the gasifier for example. What size of installation will it be to run such a unit and what will the woodchip consuming be approximately? What size boilers/water buffers would you need to make use of the thermal energy as well? Recently I found a couple of 70 kva generators with Cummins LPG powered engines, are they easier and more reliable to convert than a diesel engine?

I own a sawmill, that’s why i have the generator. I have a tractor powered woodchipper as well to do small chipping jobs for other people and companies, so if I get payed for chipping jobs in winter, I can get ‘free’ fuel.


Depending on what you mean by chips, they’re a very annoying media to work with for fuel. Some have done it but they designed the gasifiers around that fuel entirely.

Stationary adds another hurdle for woodchip fuel, lots of bridging.


Welcome KoenS. We also have a KoenV. Hopefully you have read the thread Tractor on Gas where Tone converted a diesel tractor to run on WG. He did excellent documentation of that build. The thread is long and his project starts somewhere near the middle I believe.


What kind of chippers? There is a difference between what is called a ‘chip’ depending on where you are.

Woodgas doesn’t have as much energy as diesel so power output will be derated by over half.

Look for hypermiling on this site, and that gives you an idea on how to run diesel and woodgas. But I think you would want something slightly more sophisticated for power production.

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I have a PTO disc chipper, producing G30 like wood chips. Plan is to dry them, and sieve the fines and the bigger particles out. So everything between 15-50 mm is the target.
I will take a close look at the Tractor on gas topic!


Hee Koen, goede morgen :grinning:. I think a dual fuel engine like a diesel is perfect. You can always convert it to sparks, but I like the dual fuel more. Tone is showing very nice results. Kristijan played with the compression ratio had didnt notice less power on woodgas. I am reading mostly, fixed a new gasifier yesterday. Just because I had some time. My goal is chips / sawdust for fuel. To many projects and dont know where to start.
Where are you located?


Goedemorgen :slight_smile: , it’s more that I ran into the cummins generators with the gas engines on the internet. They have Cummins GTA 5.9 litre engines. Can imagine that it is easier to change it to wood gas than a diesel, cause the pump etc. needs to get lubricated by diesel. But if it is possible to easily switch from woodgas to diesel, it can be very handy. When I start up my mill it needs lots of power, there is a 22 kw engine on it. When the wheels turn it draws 25-30 Amps. Maybe I can start the mill with diesel, and slowly mix it on woodgas. I have no idea or that’s possible, totally new to woodgas technique!
I’m located in the south west, in Zeeland.


I am also located in Zeeland- only in west Michigan. The Dutch settled here in the late 1800’s and early 1900’s and we are surrounded by small villages like Vriesland, Noordeloos, Groningon, Overisel, Benthiem, Zutphen and Graafschap. I grew up hearing a lot of Yankee/Dutch jokes :smile:


Good morning Koen and welcome to the DOW.

Search anything of Patrick Johnson or woodgas South Africa . Below is one of his videos .



We have a thread for sawmills KoenS. Obviously yours is not small or homemade, but it would still be interesting to see what you have and hear of your experiences.


That’s an interesting thread. My mill is now located at my brothers yard. We went to our ‘new’ home last year and still haven’t had much time to move the mill over here. Mine is not home made, but it’s an old Mebor that needs a lot of improvements and home made add ons :wink: Hopefully I can move it over here this winter and start milling again. It’s not my main job, more like an out of control hobby…


Haha that’s cool! I’ve heard from Holland in Michigan, but never that there is a town called to our province Zeeland!


the all power labs power pallet uses between 1-4cm chips dried to 25% moisture content. I would say you are in the right range.

Cody is right there have been numerous issues with bridging. and I don’t think you can use drum chipper chips.

You might also consider changing chippers. A lot of people use the leftover slabs and chunk them with something like a WK’s chunker, or laimet or rebak which give more consistent sizes. to eliminate the sorting part.

you will also have different results with different types of wood because of the density of the wood.

I know it is a hobby or side business type of operation, but you might also look at microgrid types of solutions ESPECIALLY if you are looking for expenses for tax write offs. I am thinking like an inverter and a battery bank then possibly add solar to it down the road. In the video, the harder he used it the more diesel he used. The trick is run is you can run it longer on woodgas and use less diesel with the batteries. Solar is ultimately a cheaper form of energy but it probably isn’t going to be generated in enough quantity when you need it. However, it is an awfully handy system to have for your own house and can fill up the battery packs. I also wouldn’t skimp on the battery packs and would be looking at LiFe batteries because of the number of charge cycles, they just last significantly longer time so the per charge cycle cost is less then lead acid and less mucking around. (but they do perform poorly in below freezing temperatures so they need to be warm).

What I am really saying is evaluate your overall energy needs, and you can use this as a jumpstart to building equity in an energy system that can supply your needs. Because even if you don’t have a sawmill, an EV charger is going to draw 50amps for several hours, it isn’t like you are going to end up with something you can’t use in the future.


In Germany and England there are sawmills or farms that have gasification installations of Spanner RE2. Those installations are really slick, but way too expensive for me. Our connection to the grid is only 3x25 A and if we want to upgrade it gets expensive, and over here we pay annual for a bigger connection. The potatoe storage is 6x1,8 kW and is used in winter and spring when there is not enough solar power. Was thinking of a combination of solar and wind for the daily usage. But my mill and workshop are more peak users. That’s why I need the generator. But diesel prices are about 1,60 per litre at the moment… I hope I will get uniform enough chips to prevent bridging in the hoppers, but I don’t know or bridging in the gasifier will be a bigger problem? I can change settings of my chipper to get G50 chips. When I sieve it more coarse the bridging could be less. The fines I can use to upgrade our fields.

The combination of diesel and gas would be good for me, but how will it react when I start up a big electro motor? Now my generator grunges a bit and puke out a blue/black smoky cloud and it continues :smiley:


Actually I was assuming (incorrectly) you were disconnected from the grid and only using the generator to get around the 3-phase AC grid connection charges. But a micro-grid (or off-grid) can be configured to only draws power if you aren’t generating enough which is probably what you are doing with your ac now. But you are really trying to utilize the farm backup generator. :slight_smile:

I won’t say it doesn’t get expensive to do micro-grid either, but there is a payback period at least, and it covers backup generation if the grid goes down issue. Which is a larger issue for you since potatoes need the airflow, and I am guessing that is a large part of your primary income. Battery storage buys time and integrates with your solar and wind solutions without a larger interconnection.

Batteries could help with this as well. then the generator doesn’t waste the fuel with the big blue smoke as it tries to catch up. (the short burst itself doesn’t justify the cost of batteries.)

To be quite frank, a lot of people use batteries to cover the startup burst of electric motors because 3phase AC is charged differently. In the states, it is based on total kwh used PLUS a line charge that is based on max current draw (yearly and monthly). EVEN if you only use grid supplied AC, the batteries covering the electric motor startup reduces the line charge part of the bill and have a payback period all by themselves through an avoided cost. It is called ‘peak shaving’ It is used a lot more in manufacturing and commercial buildings.


Hello Koen, interest in alternative fuels has grown a lot, even in my neighborhood some are seriously interested in wood-fired power. So, if I briefly describe the operation of a diesel engine on wood gas once again. Wood gas is a high octane fuel and can be used in an engine with a compression ratio of up to 1:16, I do not recommend a higher cr, ideally cr 1:14. The diesel engine works on the basis of self-ignition of diesel fuel, which gasifies and ignites in contact with hot air, if wood gas is mixed with this air beforehand, it also ignites and does the job, well, if we increase the proportion of wood gas to a ratio of 1:1 against the proportion of air, we must strongly mention the injected amount of diesel fuel, the limitation limit is somewhere around 10%, or in other words, the amount for engine idling. Combustion is fast, as it takes place at high temperature and high pressure, so there is no need to increase pre-ignition, the engine works stably and power loss is minimal. Everything seems complicated, but if you understand the operation process, it’s very easy, but the production of quality and clean wood gas is another story, there are many models of gasifiers described here, and it’s up to you which one you choose, or which one you can afford. to make.


Ours is 3-50A and I am working to bring it back to 3-25A. Haha , not possible anymore because there is to much PV. Next problem…project.

In Belgium they have a sort of the same system. Maybe in the future in the Netherlands too. The grid is working on his limits with all the pv installed last years.

There is a nice Duth design again for agriculture. The one with wooden blades. You see them a lot lately. Might be one for you. To bad Lagerwey went bankrupt.

I just installed Victron and still working on the ESS and experimental LiFePo4 battery. But wich inverters are used for this purpose in the US?

Cant find the CR of my Lister HRW2. It only says B.M.E.P 6,13bar/88,9 lbf.in2. What do you think? Will it be ok?

Well Koen, a nice warm welcome it is. :grinning: And we have a village here too with the name Zeeland, near Volkel the airbase, not far from Dutch John’s place

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Welcome to the site. I was just skimming the thread. Two points it might be hard to get the generator to actually make the correct voltage on wood gas. The motor will definitely have less power and probably a lower RPM. An electric motor probably won’t notice the frequency being off a little but there is a solution involving batteries and an off grid power setup that has been discussed here before. You can use a wind turbine charge controller to connect the generator to the batteries that system will not care if the voltage is off. A hybrid inverter will definitely not like a generator that isn’t making the correct frequency. Just something to kick around if you want a full off grid system with storage.
As to the question of how will the generator handle the big electric motor. I would look into a soft start circuit for the motor. The circut you need depends on the motor i suspect you are talking 3 phase power. But a soft start would be much easier on your current system too.

I don’t have time to look up much at the moment, but you want a small subset of something like this:

The only concern i would have is making sure the 3 phases are balanced or the controller can handle it. Because i ran into 5 papers that talked about unbalanced 3 phase which makes it sound like an issue. And it is pretty common to pull a 120v leg off for lights.

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Good Morning (here) Koen, and welcome to a forum that I enjoy and get a lot of useful info from.

I do not think Patrick is going to answer you. He emigrated to Australia about 4 years ago. Many reasons, but one of the primary ones was that his (Zulu) workforce had explained to him in very precise detail the process, and the specific body parts required, of the shaman (magician/tribal “doctor”) making muti (tribal medicine) from the beautiful golden haired little four year old girl that he and his wife (Heidi??) had.

I was the second last person to whom he demonstrated his equipment. (My son was the last.)

He did indeed have a TURBOCHARGED 6 BTA - and he did something to the turbocharger. Bigger? Smaller? I cannot remember. The gasifier was a WK with a 44 gallon hopper on top. I do not know the specifics of the insides.

He started the engine (I think he said his farm together with the sawmill required something like 130 kW) on diesel, and let it idle to warm up. This used about 2 litres of diesel per hour - he had a glass jar set up (the one in the video posted by Wayne, here) which showed both the return from the diesel/injection pump and the additional diesel being drawn in from the 25 litre drum visible in the video. He would then spend 10 minutes or so cleaning ashes and “wood vinegar”, filling up the hopper etc, and firing the gasifier. Once he had some temperature (I am not sure what temperature but it was WAY below the true operating temperature of the gasifier), he would push the throttle to the stop and switch over the farm and sawmill from ESCOM (the national power grid), to the generator. You could see the diesel being drawn in through the glass jar. If memory serves this equated to more than 20 litres per hour. Then he would switch the intake of the engine to woodgas, pulling through the gasifier. Temperatures rose quite quickly, attaining true gasifier temperatures in about 5 minutes. As my son said to me, those five minute’s worth of gas was DIRTY gas. Then, over the span of about 2 minutes, the exhaust smoke disappeared (only a stream of heat visible), the NOISE became much less - and the diesel being drawn in through the jar turned into just a DRIP. He never touched the engine, or the throttle, again. It was all managed by the engine’s governor.

One interesting feature that he demonstrated was that he had a separate (vertical) throttle body of his own design and manufacture mounted on the intake manifold. This had a flap as throttle, closing from the inside, hinged on the intake, and with a counterweight on the outside. He would start a 30 kW electric motor, the governor would add diesel and the flap would be sucked open immediately - it was just like when operating only on diesel. Over the space of a little bit of time the added suction would pull harder on the gasifier, the gasifier would supply more gas, the throttle flap would slowly close and the whole shebang would smoothly run on woodgas.

What he illustrates in the video is the fact that he used less than 20 litres of diesel per day running that generator at full load. He also shows (but is not clear about it) that the voltage never changes and the frequency (50Hz here) is also perfectly stable all the time. He refilled the gasifier once, over lunchtime, and told me that “we can now come back to shut it down tonight”. No supervision required.

I asked him how much wood he used. The reply to that was “I used to throw away 4 tonnes of wood per day. I now throw away 3 and a half”.

The wood was really offcuts from the process of making split poles. Pine, about 3,5 inches square and 3 quarters to an inch thick. Much the same size as the old 30’s cigarette packs.

Patrick still uses, from time to time, an old email address that I could supply if needs be. Got to be careful, here.

Hope this helps!