I don't know of any charcoaling courses coming up, but I'm going to start running them again in my woods near Exeter as of next year with luck. I have a proper kiln that lives there and the chap who owns it is one of the best wood colliers that I have ever met (Alex Arther, trades as Chew Valley Charcoal), so hopefully he will be running the courses for me
Until this year I had either bought it in or made it myself in oil drums. The oil drums are easy, but the % yield is a bit rubbish compared to doing full sized burns. An oil drum would give me about 10kg of charcoal I guess and I would normally load up to 3" diameter (preferably split rather than rounds as the bark can slow down the pyrolysis). I found the best use of time was to run two oil drum burns simultaneously. That way I could load the brown ends from the previous burn into one kiln and then have fresh (dry) wood in the other. I found that getting good conversion straight off the bat wasn't really possible; there were either too many brown ends or too much ash and blown charcoal.
The system I opted for was to cut 2" square holes in 8 places around the base and then have a lid that I could prop up or seal off on the top. Stick some kindling in the bottom and load the wood in with the bigger stuff nearer the top and the centre, where the most heat is. Light it with the lid off and when the smoke is too thick to get near, go up to it and place the lid on with a 1" thick stick propping it open. that makes sure there is enough air to draw the heat through, but not so much that you have an efficient incinerator
Then when the outside of the drum is too hot to touch (ideally when a drip of water sizzles off it), drop the stick out but don't seal it, you can also close off half the holes at or a bit before this time. Then just watch for the smoke to diminish and change colour from yellow, to white, to blue; when it's blue you are burning charcoal, so ideally close it all down (seal up smokey leaks) just as it goes blue. Then leave over night to cool.
I looked at the Hookway retorts and they are great bits of kit. Most of the top end commercially produced charocal and biochar is made with a retort and the Hookway is the most economical out there (ie, it's about 12 grand cheaper than the next available set up!). James Hookway also sells plans to build your own, either from an oil drum or from brick/stone. I got the plans for a tenner I think it was and it's not hard to make one, but I just haven't got around to it!
