To see some ways of making bio-char check out youtube.com and search bio-char and terra-preta there is one where the oils are collected with an extremely long tube used as a condenser. One of the easiest retorts you can make i found at this site.
MAGH CM-II NATURAL DRAFT T-LUD WOODGAS STOVE
I plan to make one out of an old hot water heater and use it as a barbecue as well. I don't know if it will work but I'm going to make a second top half that will have a chimney and I'm going to put a trap in it where charcoal can be loaded and then charged with the smoke vinegar as the smoke travels through the chimney.
