Some time ago, on a forum about making charcoal, a question was asked about using green vs. kiln dried vs. even using rotted wood. After reading that, I simply had to do some tests. I recently tried out some charcoal that was made with willow branches that were semi-rotted. they were at the stage where the bark had all peeled off and the wood was just starting to soften (bigger branched could be broken by hand fairly easy.) The BP made with this charcoal was HOT!
Since I recently made the jump from 2" to 3" shells, I've been doing testing on design variations on 3" can shells. Saturday night, I used my rotten-wood charcoal BP for the lift for a 3" shell. The shell weighed in at 288 grams, so I used 25 grams of powder for the lift. The first thing I noticed was the lift was very loud. Next, I noticed the shell was still in rapid ascent mode when it burst. The time fuse for the shell was approximately 3.5 seconds. The burst pattern looked a bit oval due to the rapid upward motion. The last thing I noticed, my 3" gun was blown apart!
So, you can make really hot BP from charcoal made from "old" wood.