Charcoal kiln, Kursk 2.0

Finaly l got some time to get back to woodgas, and it all starts with fuel prepp!

Last year l bought this 3m3 tractor cistern. Now its time to make it do some real work!

Started today by clearing the spot. Got lumber in order and cleared the old insulation l got for free at some company. Beer break then l hope to get someonehelping me load the thing on the tractor trailor so that l canbring it to the wealder.


Hey, I am looking forward to seeing your latest version of the Kursk. I cut a bunch of trees down by my place this year, and needed to burn the slash right away. I did not need any engine grade char, so I decided to make biochar out of it. Anyway, the system was dead simple, and it makes a LOT of charcoal. It dawned on me that there is no reason I could not have simply sorted out the fines and had engine fuel for very little effort. Here is the setup:

the pit is about 10 feet long and 4 feet deep. I lined the sides with cob (sand mixed with clay) and that fired into a nice liner that kept dirt from mixing into the char.

I raked the sticks to one side and quenched with water. Its pretty easy to put it out, and the heat in the bottom dries the layer at the top right away. It was bone dry when I dug it out.

I was burning branches from fir trees, so it made lots of fines that would have needed to be screened out, but with larger feedstock, I suspect it would basically burn down to being about the right size for a gasifier. I wet all of this stuff down to reduce the dust and make sure it was out, but it is bone dry in the pit.

Anyway, that first batch made about 1.4 cubic yards. I spent a little over 3 hours feeding the fire, and another couple hours to wet it all down and transfer it into sacks. It appears to be very well charred, but it would probably still be wise to only run it through a downdraft. I like that it is a good way to get rid of slash or anything that is too small to bother with cutting up for wood, it is literally dirt cheap, and it works with green wood.


Hi Carl sometimes the simple ways are more than good enough , clever idea of yours to cobb around the pit , because when i did this hole in the ground i ended up with so much baked clay/earth in the mix it was a pain to use , i now have a hopper from a 3pl seed broadcaster i use to burn down my small bush materials from the property into helps keep it off the ground and cleaner for me .


Carl, this is fantastic!

The leafs charcoal shuld work great in the garden as it usualy contains moreminerals.

Tryed that last year but our soil and clay was too crumbly for anything more thain garden charcoal. Tryed to run it in my MB once or twice and all l ended up with was a ball of expanded clay in the gasifier :smile:


Yeah, I think baking the sides of the pit into a solid ceramic lining would be the key to make engine grade stuff. The nice thing with such a big pit is that fuel processing becomes negligible. I could toss in whole 10 foot long branches, and they just burn down into dice-sized pieces of charcoal.

I saved a big pile of limbs that I was going to chip, but I might save some to do a test batch this fall when they have dried. I have an enormous stockpile of charcoal, though, so what I really ought to do is work on another charcoal gasifier… Maybe this fall I will make some time.

Remind me Kristijan, what happened with the original kursk? I seem to remember that it got hot enough that some of the metal warped, but did you do enough batches in it to get an idea of how long it would hold up?


The original Kursk is still functional apart from some design flaws but we moved to our new property and left it behind.

Problem was first, not enaugh insulation. It got wet touching the sides and it then became useless. Second, it was hard to load and unload with the top door. Third, the burn place was flooding from rain. Fourth, the emptying door was hard to seal.

The new one will have a burn zone in the actual kiln. No part of the tank will ever be directly heated and the burn place concidered expendable and easy replaced when neaded. Everything here is round or dome shaped for stability too.


Mud mud and MUD but determined to get it done!



Now THAT is an absolute unit!
Funny that you call it the Kursk after a submarine, in the illicit alcohol distilling business guys will make stills out of tanks similar to that and also call them Submarines.


Okay the wood goes into the larger barrel and is sealed, and smaller half barrel is the fire tube heat source for baking the wood. Are you using a rocket stove for heating the Kursk?
Will the gases coming off the wood be recycled back into the firetube for more heat?


I like pic no2 to the left = thinking chair :smile:


I prefer standing next to my project and staring at it for a long time, then forgeting what I was thinking about on it. And having to walk away from the project to remember what it was. Then remembering the previous thought I had. That I also had forgotten about. You can see why it takes a long time to finish anything. Kristijan does not have this problem obviously. He a geter done type of guy.


Hahaha! :smile:
Bob, you nailed it. My memory works exactly the same :smile:
We may not be twins, but obviously the same area of our brains fried :smile:


When they say retrace your steps they weren’t kidding. I have times like that a lot. Maybe we all have some kooky thing in common that also correlates with Driving on Wood.


Does carbon monoxide poisoning cause memory loss? Now I cant seem to remember… :grinning:


Or walk to the toolbox and blankly stare trying to remember what tool you need. Proceed 2-3 minutes. Start walking back to the project to refresh your memory and click that’s what I needed half way back to project! Spin around head for tool box, become distracted by parts delivery, shiny object, wifey duties,the fridge full of brain oil goods between toolbox and project, coffee pot, the pile of projects stacked atop the toolbox on the “healing bench” ect ect


I just realised l never gave a update!

The kiln was set.

I put about 6" of fiberglass over it then l will plaster it all over to make a hard shell.

For a test run l threw all kinda junk laying around. Most at least wet wood, some even green.

First fire

It was 8 in the evening and l had a neighbour come by, curiousity ofcorse. Adding on twigsand limbs in the fire, 3 hours and quite a few empty aluminium cans later it reached criticality.

Fire in the chimney

For refference. My old Kursk neaded 8-12 hours of warmup and reach criticality! Im amazed.

So, l waited for a bit then decided it doesent have enaugh draft to cause a supernova event, exess gas produced vented its self out by sufdocating the flame so l went to sleep.
Next day.

No need to say any more. Its all but a few logs at the door that turned in to hard, ringing charcoal. Fantastic. Now l need a gasifier :smile:


Kristijan is back. Watch out! :grinning:


I have been following this and wondered why you call it Kursk?

Quite the tank/pressure vessel you got there, reminds me of the guy from Vietnam that used to live across from me. He was building a submarine in his garage… He did not want to explain himself though and for a very long time I wondered about the giant pressure vessel HA HA.

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This is a very good thing too. I better get my double flute gasifer built finish. Or he will have one up and running before my next progress report.
As a matter of fact. I am going to go out and start working on it right now.
Bob signing off to play on the the dark side.