Well I finally did it. Got some kilns out in the woods to burn slash piles that are normally incinerated to ash. Thanks to Grayback Forestry and Sean Hendrix for inviting us to bring the kilns to see what they could do. Each kiln consumed about 6-8 burn piles and made close to a cubic yard of char. It rained steadily all morning, but we were still able to make char. We lit up at 9 am and quenched at 12:30. I was pleased to see it took less than 50 gallons of water to completely quench one kiln. Took a lunch break and dumped the kilns and loaded them back on the trailer. Went pretty smooth, really.
Some of the Forest Service fire people were there and they said that 7 piles corresponds to about 40 feet of roadside thinning. So if you could unload 20 kilns along 800 feet of roadside, you could treat all the slash and make 20 cubic yards of biochar in 6 hours of work. If the feedstock is well-staged and you don't have to pull apart piles and move it long distances, I think one worker (a young, strong one, not me!) could feed 4 kilns continuously. So a crew of 6 could do it. You'd need a flatbed to transport the kilns and 1000 gal water truck to quench.
The only part I have not figured out yet is how to gather up the biochar for bagging. I'd like to try a shredder vacuum, but I worry about wet char sludge clogging up the works. Otherwise, a loader with a scoop could pack it into totes for sale. You'd get a little forest duff in the bags, but that's a bonus extra!
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