Mr. Charcoal (Automatic Firewood to Charcoal Processor)

Ok here is a concept Ive been carrying around in my head for quite a few years.

The idea of this, is for use as a primary heat source using standard cut and split firewood while rendering charcoal as a byproduct. So in concept during a first light up it will run in a bypass updraft mode. Just like most ordinary wood stoves. So you fill it up and get it going until its good and warmed up. Then you switch off the bypass gate it runs in a downdraft mode. Bellow the primary air input is a set of rods with fingers. Sort of like a rebok chunker but instead of blades there are finger the poke into the char logs and chunks to break them up into small pieces. From here these pieces then fall down into an auger troft. There are three bars that span across this troft and spread 4 inches apart. So larger pieces that make it through the buster, will further be broken down as the auger tries to push them past these bars.

Primary combustion gas also passes through the buster mechanism, but right after it is redirected updraft and too the outside walls of the burn chamber. Second stage air is introduce immediately after this transition so the ambers and established combustion will keep it lit. Fire brick will be used on the outside housing of this passage chamber. Once the gas enters the top is then directed to a heat reclaim with a forced air blower to direct heat out of the unit. This will have a backside exhaust outlet so it is more universal you can go through wall or through the roof.

Dealing with the charcoal indoors I think is a no go. So this will have an auger drag out that will take the char out through wall to an outdoor barrel drum container with a sealed lid.

I have no idea if this will work at all lol. But ideally I will be able to control how much char it produces verses how much heat is produces. For instance during the day I may run optimized for charcoal production, but at night I will want a full nights sleep. So this thing will need to still be burning in the morning. I think if I control the buster speed to a crawl or even stop it, then it will act as a static grate and the fuel will burn to ash. No biggy the auger will pull it out. You will still need to screen the fuel so ash isnt a worry.

Ill post more detailed pics later, Ive been working on this from the time I woke up till right now. :fire:


I like that idea a lot!
Would like to see a diagram of the internal workings.


Ok here are some more details;

Here is a section view, the core is the burn chamber, the chamber to the sides are the second stage combustion process. Then outside of this is just the enclosure that will have lined firebrick that will be sandwiched between this outer chamber and the enclosure panels.

Here you can see the angle bars with the holes drilled at the top side. This is the primary air feed and the idea is to point up to increase dwell time and to better saturate this zone for thorough combustion process. Bellow are the buster shafts. There are support plates that run along the shafts to act as journals to support the shafts and also aid in breaking up the fuels. Then you have the auger trawft where the fuel falls into for the auger to drag it out busting up larger pieces if too big to pass through the bars along the top.

This here is a closer look at the secondary air feed tubes. You can see the series of holes drilled point at the path where the gas is transitioned back up though the outer chamber.

Here is the unit with front and back panel. Note there are slots in these panels to install the breaker bars. They will insert sort of like a cam shaft. These bars will be a consumable part. They are drive with a gearing system just like a rebak chunker. However this will turn very very slow at very high torque. I do expect this make annoying noise as it functions. Hopefully it wont be too annoying.


Just to note, this buster system may not even be needed. Just a very loose grate system maybe enough to let produced char through. Then the auger will smash it up. A few years ago I built the fire pits and those had a grate with a 2" or 3" grid. Lots of char fell through this grate. So this breaker system maybe beyond the KISS method. But Im going this route first as will be able to test this with the buster bars removed.


Actually that maybe exactly what Ill do. Is bring those busters slighter lower and closer together then add in a loose grate above. This will ensure the fuel is processed enough to be busted up.


Ok so made some revisions and added the passive grate. There is about 7 inches from the grate to the center of the buster shafts. I also changed the busters from pins to triangle plates. I think this will have more integrity while also making them less aggressive and some what passive.


Did a lot of detailing today and some things to reduce cost. Those spur gears I specked are ridiculous they are 100 bucks a piece. I did away with the gear reducer and will go to a chain drive driven by a lower cost DC worm drive motor. Did away with the mounted bearings and will go to press in bearings that we make our own housing for. The electronics will be simple just an AC to DC power supply a programmable cycle timer, fan speed control and that will be basically it.

I estimate retail pricing to be around $3500.00. That is low compared to other high end stoves that dont have nearly as much going on as this one does. This thing is much more that burning wood in a box! There are other stoves well in the $5000 range that are not nearly as complex as this stove.

So today I detailed the front and back panels, added in the heat exchanger, exhaust outlet and created the ducting to vent the reclaimed forced air heat out the front of the unit. I designed my own gears we will cut with the CNC machine. Plus the revisions I made for the buster system and the added passive grate. Still more to design build yet. I need to add in the door latching system, hinge, create the worm drive motors and add them in. fastening system for the front cover and then create the new bearing set ups.

Then I will move on to the charcoal gasifier units. I will be bringing back the Fusion gasifier design and re working it for charcoal. It will share existing touch screen automated systems with electronic air fuel mixture system, self ignition and flare lighting full valve control and all other automated processes existing machines currently have. The charcoal gasifier system will have a large top feed hopper with an updraft reactor. However it can be recharged on the fly like a down draft. It will be built sort of like the experimental kit machines I built last year. It will have a liquid cooled reactor with steam reformer. The blower will be the Amtek blower that is crazy powerful. My target pricing for this will be around $4500 ish. Just the electronic alone is $1000.00 bucks and thats just for the parts. Steel, paint, seals, hardware, all the plumbing fittings, hoses for the steam reformer, hose attachment system for the engine connection; all that will come to another $1000.00 at least. So then I have overhead, building cost, shielding gas, grinder disc, torch tips. band saw blades etcs. Im looking at a months build time it takes a week just to build and wire the panel. So yeah it will be expensive at this level. However I may offer a bare bones version. I could probably build just the gasifier, no electronics, no engine kit, no blower, no valves, no auto ignition , just gasifier for around $1500. I plan to crunch it down some as I can shed the reduction zone and the ash bin and condensate chambers can loose some volume as well. I think i can get it down to stand just 36 inches tall and it will boost a fairly larger hopper :fire:


You might scavenge the charcoal fines with some of the air you are moving around.

I wouldn’t blow them directly into the combustion chamber - combustible “dust” entrained in fresh air is an explosion hazard. But perhaps a cyclone above the combustion chamber could filter the fines out, emptying them out the bottom in a metered, safe way.

I’m always super impressed with your visualizations Matt. I know that’s years of experience at work. My ideas are all still stuck in my head, while yours get out - first in pictures and then in metal. Well done.


Yeah it actually takes longer to design a machine than it does building them. Well thats if I fully detail the machine and then after it is designed, With out design then you build it three or four times and it wont be as good as if it were designed. The nice thing about CAD there are no limits and if something dont work, nothing is lost other than some time. Just tweak it until it works. :fire:

Im not sure I follow you on the dust. In the combustion chamber its raw wood there is no dust here at this point. There will already be combustion established at the second stage and those rotary busters will turn extremely slow, less than 10 rpms. The auger will only run at 40 rpms and char ash brought to barrel will deprive it from oxygen both heat and combustion will drive it out of the barrel. The barrel will not have the band clamp anyways. Too much a pain taking that on and off. Ill just use the spring loaded latches Ive used in the past that work very well with the barrel lids.


Matt that seems like an amazing idea for charcoal generation. I have pondered something like that but have nowhere near the skills to make it real. I hope you end up developing it…
Cheers, David


I too have been thinking about this probably since l started the woodgas buisness…

Even tryed building one! For my greenhouse heater. Unfortunaly l never got it to work. Had other issues too, like not enaugh draft. Pictures, videos and tests somewhere on this site…

What l learned is a loose grate has its problems. Have it too loose will resault in bits of partialy burnt wood to fall down. Specialy a problem with a auger! Firewood is never uniform either… kindling and small logs can fall trugh and make a mess.

I think your rebak style double shaft grinder is a bit overkill. When a log burns its outer lair of wood to char, usualy it falls off in chunks by the lightest touch. Just need a mechanism to gently poke on the logs, and char will fall down.

You culdnt come up with this topic at a better time! I am building a new house and am planing to make the wood heating system my self. Char making is a feature l planed to add on later years, but since l am planing stuff l might allso plan for that…

Keep up the good work!


Kristijan, I didn’t realise. I was under the impression you were about to renovate the existing one.
Looking forward to some interesting updates on your thread :wink:


Kristijan, is your new heating system goingto be a boiler?

Well yes and no. House will be small and there is more sence (and cheaper :smile:) to go with radiant heat rather thain plumbing and radiators or floor heating. But l need hot water too. So its gonna be a combination probably.

My great grand mother has a neat system. A cooking stove with a massive bread oven (brick) and a water reseroir inside. Not sure how exactly its made but l like the idea to add some mass to the system.

I just did some thod on this actualy, charcoal production will probably not happen here. Simply because it wuldnt be worth it. We burnt 2 cords of wood this year and during the night you need that char anyway so you dont need to start a fire in the morning so that splits it to half. Most of the day the wood burning cooks our meals char is allso neaded there. The rare occasions where char culd be harvested dont justify investing in the system for me.

If it were for our previous house, thats a different story! The boiler was lit every day for hot water and burnt as much wood in summer as in winter. A lot of wood all together that culd be turned to charcoal 90% of the time. Looking at literal tones of charcoal made each year!

Right now it makes more sence to me to just get the Kursk 2.0 kiln runing :smile:


My thought on this is, we are making charcoal as the primary product. Then we are salvaging all that wasted heat for something we also need.


Well in house heating its the other way around. Kilns are hard to “throtle” and usualy work per charge. Not practical for a household except if you invest in a huge heat storage tank.


Long term goal, I’m thinking of installing a big (or multiple small) underground (or basement/ root cellar), insulated “heat energy” storage tank/ system. Use for passive solar, waste electric (wind generator), waste wood fuel, waste heat from making charcoal, etc. One tank, one fluid medium (treated water), many sources. The spirit is willing, but…One of our largest expenses is winter heating.





Already around 1930, an Italian had thought of not wasting heat to obtain charcoal, not electronics and it works perfectly this stove …

I forgot, with hot water production …


Yeah my pellet heater died this winter. So this is going to be the replacement. I have not quite figured out hot water yet. But I think Ill probably end up using exhaust heat from the power unit for this.

Good to see that how Ive visualized this is how it works. Those breaker shafts are designed so that they are gentle and also so that if hard wood makes it way to them, they will not be able to grab it. If the triangle are too aggressive then Ill have make them less aggressive, maybe the next version will be square shaped with large rounded corners. I did foresee the char crumbling up on its own, but if we take it too soon there is no foundation to sustain proper combustion. Like our gasifiers there will be processes in layers and all processes must be sustained in order for this to work properly. Char should fill up above the breaker system, This breaker system intently will feed out the char very slowly while also breaking up larger chunks. I also forsee, fuel will need to be uniform both size and dried. You will need full length wood, no small pieces, uniformity will be key to this working.

Yes at night this is my biggest frustration with wood heat is waking up a cold house. That is the last thing I want to wake up too. So a 10 hour batch run time is the criteria