I thought I'd share a recent video I put up on youtube that documents an incredibly simple way to make charcoal / biochar in an existing woodstove that is clean and efficient... It uses the off gasses from the process to fuel the fire to cook food and heat the house, rather than a contraption burning outdoors that is only making charcoal and heating the world at the same time. Thought people might get some use from this...
Would love to hear peoples experience or notes on this approach.

Very nice little set-up! I'm inspired to start making some biochar in our wood stove as soon as I find an old roasting pan with a lid. Much simpler than building a contraption, and a good example of stacking functions. Thanks for sharing Sean

Thanks, yeah, at some point I'll post an update video with details on how it's working (which overall is excellent). Some notes on safety in the short run if you are doing this... Have a wide tray (like baking tray) available to put under the 'retort' when it comes out of the stove to bring outside, rather than trying to carry it with gloves, since it's hot and there may be coals still stuck to it, and let it sit to cool ideally overnight outside on a stone or other unburnable surface before you open it as it may/probably will reignite... Perhaps find two similar roasting pans so you can switch them out and keep them going. I do about 10 batches a day, it's reduced my firewood use in half and provides super clean, hot fires to cook on...
Best of luck!