I used exactly 100 pounds of wood. i got 29.49 pounds of engine grade, tar free, charcoal and 3.41 pounds of uncooked wood. This is an old water heater I converted to a TLUD (Top Lit Up Draft). I live in Colorado where we have a very dry climate, so my wood was very dry. And it was a very dry day, 21% humidity. I suspect that if you live in a wetter environment it will be more difficult to get these results.
Rindert