Your comments on the charcoal issue is right. This information is for the people who would be interested in charcoal making.
Not properly dried wood will never yield more than 20% charcoal and most of the pieces will be broken. Charcoal which is not broken in pieces, burn longer and gives more energy. In the market what is called Grade A charcoal, brings 30 to 40% more price than lump charcoal. What is most important today is try to make charcoal as clean as possible environmentally, even in traditional kilns.
If the wood is burned too fast and not dried, average yield from the traditional kiln will be 25% charcoal which 35% will be Grade A.
We have been doing research on a new way of making charcoal from Bulgaria, Turkey and Indonesia. New regulations from EC, makes companies search for alternative way of making charcoal even cleaner than retort systems.
After many months of trying in lab and field tests shows, the results are impressive. Only release smoke contains water-steam from drying wood in kiln, all the rest of the gases burned in process, carbonization takes about 6 days for 4 m3 kiln. From Oak wood, we get 36 % average yield of charcoal which 68 % is Grade A.
This is an important issue when it comes to yield of charcoal and how clean it can be produced.
Robert S. Kana, Biomass Energy, Indonesia