Great info Bro,
Necessity works wonders for ingenuity. Thinking on that project for charcoal, it makes wonderful sense, and simplicity is awesome. As fro trapping the gas, a copper line from the hole to the storage unit. If your doing pine, you can also distill the gas for wood spirits (turpintine), or so I've heard.
Sounds like a realatively quick set up too after scrounging the materials. Hard part is chopping the wood. And for practical purposes your smithing fuel becomes free.
BTW how long would it take to char a can of wood? And how much fuel was used to char the can?
You also realize other than for smithing, this is the first step for black powder production.
Grae
(a guy who admires primative and obsolete technology)