Gasifier Engine Driven Charcoal Production

To start off, Im putting this into it own topic as any design work I put into this is free for the taking.

So what I am planning on building is a charcoal production system that will be universal fuel input capable. (Pre processed chips, chunks or non processed typical cut and split fire wood)

This will be the kiln only, the primary thermo process and engine system will be a separate and external system.

This will be rather simple, it will have a removable basket to contain the feed stock, a Pyrolysis gas re-circulation system and a simple swirl burner below the basket with a 1 to 2 inch gap between the basket and its outer walls for combustion gases to flow through for even heat distribution. The pyrolysis gas recirculation system will feed back the gas into the combustion process bellow the primary combustion process swirl burner.

For the gasiifer engine system to drive the combustion process. I plan to build a dedicated gasifier but could also use a simple fire, or the charcoal units I have planned.

For a dedicated gasifier system, I plan to build a FEMA gasifier!! Finally a use for the FEMA gasifier. However this will be modified a little. The hearth will have air inlet jets like an Imbert. The air feed will come from the hopper so some air feed will migrate thru the fuel in the hopper. This will be a closed unit and air pressure driven as I dont want any electrical input to drive this system. Since all we are doing is burning this gas off in the swirl burner of the kiln gas quality is not an issue.

In any case this will eventually have some automation with an O2 Sensor driven air mixer valve system. The idea is to control the gasifier gas production and slow it down once the process gas from kiln becomes combustible feeding the process.

More to come :fire:


I wish designing and building a commercial engine grade gasifier was this easy. I litterally designed and modeled this in a half hour.

So this here is a sealed FEMA unit with passive jetting. If you look close you can see there are some slots in the inner vessel. These are the jets to help keep the oxidation zone static. This has a very shallow reduction with a very passive grate. So hopefully grate intervention will not be necessary. Even though the lid is not there yet, this will be a sealed unit with an air intake feed inline with one of the jet openings to allow for lighting. Ill use an ejector to get it lit and meter in pressurized air after ignition.

The bottom picture shows the upper outer shell faded out to expose the internal hopper. This outer shell is basically a manifold. Air enters in here and feeds the jet slots that are cut into the internal hopper shell and also can migrate to the top and enter the top of the hopper inside here. This should help keep combustion gases down as well.

Those looking for a stupid simple gasifier here ya go!!



Wow! Neat idea! Would like to see it in action.
Can hardly wait. Loved my little femas for making cooking gas!


Still a Fema I will never build this. However this design maybe a good one for you to play with controlling the air intake as the air entering the unit is passive. What does not go thru the jet slots will go around up around the hopper. The advantage is the hopper is no longer a static pressure, the passive air will push down combustion gases keeping fuel dry. If you can figure out how to tune this it could work.

But for me Im done with direct wood gasification. It can be done, but not with out complexity and more difficult fuel processing. I used to think just the opposite but thats no longer my assessment. I am now working on a hybrid system with an indoor stove technology that can run as a direct wood gasifier and also functions as a charcoal production system as it heats. Then the filter is a charcoal gasifier that runs on the charcoal produced from the stove. The Charcoal unit refines the producer gas created by the stove cracking the chains and reforming any moisture for higher water shift. The stove features an already developed gasifier and typically will not produce tar. But it can and in those events the Charcoal unit wont allow them to pass through its combustion process and it will destroy it.

This combined system will also double the batch run time and on the stove end you can refill on the fly. The charcoal unit will just have a larger hopper to accommodate longer run times for daily operation. The balance between them can also be adjusted.

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Can you tell us about your little femas? I want to fire an aluminum melt furnace with wood. Maybe put your reply on All About Metal Casting thread.

Hey Matt,
I’m kind of having to chuckle every once in a while in reading about your latest endeavors. As you know, charcoal is a refined fuel (when compared to wood) which makes it much easier to gasifiy and seeing you turn to the “dark side” is kind of fun. What I think you are planning is a good idea and has a lot of potential. I well remember feeding my simple fire with smoke from another device and thinking the charcoal gasifier can take “dirty” gas (like FEMA smoke) and clean it up. Sounds like you are thinking along the same lines. I never developed any further but with your knowledge, fabrication skills and marketing I hope you can launch this process.
Keep it up Matt!
Gary from PA


Yup, Yeah It took be a bit and Im hard headed. But I see opportunities to do more with charcoal that you just cant with direct gasification. Add in the stability and water drip boost its just better technology. Market perception is the hard part though.


Well, when I get some time I’m going to build a better charcoal grinder along the lines of Gary’s but I don’t see how just making charcoal is a big deal. I’m just throwing wood in a barrel and burning it while I do other things. No problem at all ending up with half a barrel of good charcoal and no effort other than throwing in another layer every half hour or so. Never bothered to try barrel in a barrel or do more with THUD. Your millage may vary.


Something else I’ve been wondering about. No one wants to hear a generator roaring away. I’m not clear on what is required for a small engines exhaust system to work well. Unlike a car engine where a well designed exhaust system moves more air and fuel through the system, most generator mufflers just look like cans with holes drilled in them. Why not pipe that exhaust into a five gallon can filled with charcoal. It would knock down the noise and dry the fuel. Dumb or what?

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It really depends on the engine. I have an old Briggs 7hp flat head. I tried putting the muffler from a 6.5hp Predator on it. It didn’t help. I would have to build a sound box to put the Briggs in. This would have required air flow in and out and exhaust out. Not worth it.
The Briggs was obtained as a test unit and so it remains. I’ll replace the Briggs with the Predator when I become a little more confident that I’m not going to ruin it with tar.

The exhaust only outputs 1/3 the noise of the generator. the other 2/3 come from the intake and engine itself. You can put an automotive muffler on them, look to a Honda civic, it does help. This is another I went to full enclosure systems and will continue with them. The Twins have much less noise and are more effective to put mufflers on. They sound like a V8 sometimes and are more pleasant to listen too.


Mr. Wrestling,
All I did was take a 12 inch long 2" inch iron pipe put a union on one end then a reducer from 2" to 1" for a grate I used the ss center from a kitchen sink drain.drop the grate inside the 2" tube so it’s above the reducer. Cut a hole in a metal 5g bucket lid that is just big enough for the reducer to fit snuggly. I glued the 2" tube to the bucket lid with stove paste, and high temp silicon caulk.
Can be used as is but made better gas with a 1" tail pipe 4 to 6" long mount on 5g metal bucket with about an inch or two water in the bottom. I mounted a 1" floor flange on the side of my metal bucket for the gas out pipe
Just below the top of the bucket. Pour a cup of wood pellet in the tube and light with a torch
For a vacuum I used a bucket head vac. from home depot with a cheap dimmer switch for a speed controller
There is no welding everything is bolted or glued together.
My second one was identical to the first except I used a floor flange on the top of the bucket lid and on the bottom side mate the bolt holes up use 4 bolts to hold it all together now drill a 3/4" hole 3" above the floor flange in the 2" tube tap thread for a plug( lighting port)
Put the reducer on the lower floor flange and the short tail pipe. Drop your grate in the tube.
For a fuel hopper I put a floor flange on top of the tube and bolted that to the bottom of a metal 5g bucket. Every now and then you have to tap the side of the tube to avoid cavitation in the burn chamber never filled the bucket because I did not have a lid for the top.
No way to shut the air off, when I was done cooking. So I learned how to time the burn with how long it took to cook say a pot of potatoes or pasta for 4 peeps. Then just shut the vac. off and let the pellets go out

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I forgot what this thread was about haha. Yeah things have evolved from this concept. I am going to work on a system that will use drums with a center reactor with automated grate to flow the chips more rapidly for charcoal production.

My advice to you would be to put your efforts here. figure out how to convert your readily available chips to ready to run charcoal. and then build a simple charcoal unit for engine running. Adapt a water drip system and you will have something more reliable and just as powerful as a direct system with out worry of tar. Think of way to use that heat to produce the charcoal for other things. Hot water and heat.


Yes. Once you’ve really used, and experienced small engine V-Twins you’ll not go back to big singles.
The larger singles all have internal anti-vibration counter weight driven systems in them.
Inertia. Weight. Frictions.
Some are excellent. Kohler Industrial. Some are real particles shedding engine killers. Kohler Courage engine series.
V-twins have no extra active anti-vibe system to have to lube and maintain.
Just that extra power making cylinder.

You do need to step up to 15-22 hp engines. 400-1000cc’s

Yep. with the best dual entry muffler the exhaust pulsed are timed to cancel each other to a large extent.
And I think the intake and exhaust tied together cylinders are dampening each other from combustion event broadcasting.


The Predator 670cc vtwins look like a lot of engine for the money, even new from a store. There are also a lot of lawn tractor sized vtwins out there of similar capacity both operational and not, generally all Honda GX670 clones of some sort like the Predator.

Some of the broken ones are nearly free for the taking and can be fixed for not much more. Eventually everything breaks so fixing one at the start sets you up to sort out future problems. You might even buy a few cheap broken engines just for spares and spare parts. I’d have a Store bought rebuild kit in reserve as well.

Given the properties of wood gas, you want a good amount of displacement and these vtwins aren’t a bad way to get it. You’ll need to source and connect your own genhead but that’s not too much trouble.


Central Georgia generator or go 24 volt DC. Yes the Predator 670 is a beast of an engine and run excellent on woodgas. That has been the case for all V Twins really. But the Predator 670 is the most difficult to find parts for and is the major factor for me to move to Honda. Otherwise I love the Predator engines, they are good engines but in the long run its better to find something you can get parts for.


There is an Ausie woodgasser on YouTube I think his channel name is CNC WOOD GAS
That pipes his generator exhaust into a can with a basket ful of wood chunks for drying and it does keep the noise down.
Exhaust in the bottom then out a small hole in the lid.
The basket holds one full load for the gasifiers


I’ve noticed this suggestion been mentioned a couple times. Doesn’t the exhaust contain enough water vapour to do more harm than good?


No Steam drying will unlock core moisture this is a common practice furniture manufactures use to dry wood. It is more effective than dry heat.


Yes. Steamed to cells crack.
Then, forced dry ventilation to truly dry.

And I should add . . . that old poor combustion high HC’s and CO emitting engines actually do have fairly dry exhaust. Stinky eyes watering exhaust.
The BETTER, more complete the combustion, the wetter the exhaust will be.
I will not; do not; use engines exhaust in direct contact to condition wood fuel.
Because I like having the most complete combustion engines running. So will mostly have hot wet, wet engine exhaust.