I took on a little project today. There are so many little bits of wood scrap left from the events. They aren't a great size for rocket heaters and I've been thinking of ways to use them up. So I took a bunch and turned them into biochar.
I followed some advice on using a pit fired method here:
Some thoughts on the end of burn, when there are still some pieces left.
1) I do basically the same process as you, but I start with small pieces to build a teepee style fire, then when it's going ok I move to the largest pieces as soon as possible so they have enough time to convert, then I move back to smaller pieces to keep the flame cap going over the fire so that it consumes the oxygen....start small, end small is my teaching mantra. I keep a rack of dried branches broken to 2' or so and sorted by size so I can toss lots of smaller and smaller branches onto the pit to keep that flame cap burning hot. The very small branches create a lot of heat and convert to char quickly.
2) When #1 fails I usually do the same as you and move the large pieces together so they can keep burning off each other and so that I can water douse the rest of the finished coals. I usually pull mine all to one side into a keyhole to finish up....basically like a keyhole firepit for grilling, except they usually pull the coals over to allow cooking without smoke, so the same but opposite.
3) If #3 fails I just douse the left over large pieces and either let them dry for use in the next char pit session or else use them as part of a mulch.
Very excited to see you guys making biochar! Ruth Stout is a great idea for it...will also be great in your sawdust bucket for the willow feeder.