Biochar kiln Update

Sometimes the solution to problems are so close to your face that you can’t see them at all.

I have been tinkering around with biochar for a while now. Recently I was at the Sound Waters Stewards expo the other day talking to folks about it. I was complaining about the fact that I could’t Find enough dry wood to use as fuel in my biochar kiln. A fellow named Jeff looked at my design and said “What happens to all the heat generated by the kiln?”
“Nothing.” I replied “it goes up the chimney.”
“Why don’t you use that heat to dry the fuel for your next load?”

Dumb, slack-jawed, silence.

What a simple idea. Use the heat from the stove to dry out the wood for the next run.


I love it when ideas like this present themselves. Solutions so simple that you wonder why on earth you didn’t see them before. Call it “creative hyperopia”. You can see the goal or problem on the horizon with laser clarity but the solution on how to get there is so close to your face that your vision simply can’t perceive it.

Barrel on top of a barrel.

This is my first attempt at making this idea a reality. Quite simply it is a small 20 gallon drum filled with wet wood placed on top of a biochar barrel. I know this is not the optimum in heat transfer and I will be trying out new designs going forward. But the concept appeals to me because addresses two of the basic design flaws in the “tin man” nested barrel retort:

a.) how to come up with enough dry scrap wood and

b.) how to utilize the waste heat from firing the charcoal generating stove.

When I first tried out this idea I was concerned that placing even wet wood on top of the kiln might pose a fire hazard. But the design of the kiln itself has a twenty gallon drum inside the firebox and all that is produced is charcoal. The key is excluding oxygen. Thus if combustion of my drying wood becomes an issue, all I need to do is put a lid on the barrel and I will be able to dry my fuel without worry that it will catch fire. No oxygen, no combustion.

If anyone else out there has tried making biochar and has experiences or suggestion on how to make my design better. I’d love to hear your comments.

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