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.