| Rice Hull Charcoal Maker
I bought a rice hull charcoal maker for 1000 yen (+/-$10) at the local home center. Think of a leaky funnel, about 50 cm mouth, with a 10cm chimney on it.
Operation-
Start a small fire on the ground, invert the funnel over it, and pour rice hulls around the funnel. As you see charred bits along the sides, shovel up more un-charred hulls from the bottom. When it looks to be about 80% charcoal, pull out the funnel, rake out the hulls, and water them well.
As a bonus, the small wood fire under the funnel has also turned into charcoal! I am going to try someday with sawdust and see if that works as well. If it does, I will be the first guy on my block with 20% charcoal soils. I will try and take some pictures.
The 150x150 cm bed I tested this on now has spinach growing in it (and quite well at that). I had about a 5cm layer on the soil before I double dug it in with some chicken manure and rapeseed meal. | 
