A long time ago I read an article that peripherally mentioned making charcoal at home. I couldn't do whatever it was that the article was really about (probably forging swords or casting rocket nozzles from aluminum or something), but I could make charcoal. However, I never actually did anything on this since I live in Chicago and have no yard where I can burn things for hours on end.
Then last month I heard something about an episode of “Dirty Jobs” where he worked in a charcoal factory, and the process was described as basically putting a sealed container of wood in a fire so that it partially burns, but not completely. I was already planning a camping trip soon, so I decided to give it a shot there.
When I got there, I found a log and sawed off some 1 inch rounds, then chopped it into pieces a little smaller than my palm. I put about two gallons of this in a 5 gallon metal bucket. Then I turned it upside down so it was more or less sealed with the earth and started a fire around the outside. I had trouble getting a decent fire going and the fire pit was probably too small to allow the size I would need, but I set it going nonetheless and left it to burn for about 6 hours. When I returned, I pushed the fire aside and lifted the bucket to find … warm wood. The fire wasn't nearly sufficient to char it all. I found a few pieces that were charcoal, but this was definitely a failure.
So I tried to figure out where I went wrong. The careful reader might notice that earlier I said I read “something” that mentioned making charcoal, then I heard “something” about a show that mentioned making charcoal. Nowhere did I say I read instructions on how to make charcoal. So step 1 for next time, read instructions. I found a couple good articles on the process. The first describes the science of charcoal pretty well, and the second describes the rig much better with bigger pictures. The second also has an interesting feedback loop mechanism where the wood is heated by burning the hydrogen, oxygen, vaporized alcohol and tar that are driven off in the heating process, ensuring an almost perfect heating duration every time. These rigs look a little more complicated than I'm able to do at the moment, but there will definitely be a charcoal round 2 at some point in the future.