Welcome to a Gardening with Biochar FAQ!
... a work in progress...
When gardeners add biochar to garden soil, we are, in effect attempting to follow in the footsteps of the originators of Terra Preta. Because we don't know exactly how that process worked, nor how we can best adapt it outside its area of origin, we are left to discover much of this by experimenting with our own gardens and comparing observations within our own communities.
Thanks a lot for all your links and infos. I have just started a small Wiki page which intends to list and compare the different companies on the "carbonization market". Hopefully it can help to get a general idea. However, I hadn't time to do much so far, so don't hesitate to contribute !
Here is it: http://en.wikipedia.org/wiki/Biochar_production