I made charcoal yesterday. Here's how I went about it:
All my projects start off with a search on the Internet. This one didn't take long; making charcoal is easy and well understood. Still, I hadn't done it before, and I picked up some interesting ideas.
Charcoal is really just "cooked wood". You can make charcoal two ways; cook it indirectly, in a closed vessel heated from the outside; or you can fire it directly, burning some of the charcoal to cook the rest of it. I opted for the second way, since it is simpler.
My wood is from the gasifier fuel supply. It has been processed into 2" cubes with a hatchet. Plenty of it around for charcoal making!
I have a good vessel already; the top half of a hot water heater, leftover from building the gasifier. I set it upright full of wood, and made some air inlets at the bottom. A little diesel fuel got things going. In no time at all, there was smoke pouring out the top:
I was worried that it was going too fast, and burning up all the charcoal. So I closed the chimney some:
And it promptly began distilling tar. Plus a good bit of moisture:
OK, so I need to let it burn some more. Opened the air valves, and let it go about an hour....then I shut it down, assuming I was done. After it cooled down, I tipped it over, and found a lot of tarry brown wood. Only a little was charcoal. But as I was sorting through it all, the smoke started back up. I think the fire was trying to tell me something - It wasn't finished yet. Patience is a virtue.
So once more I assembled the cooker, and smoke came pouring out. I let it go a long time, maybe two hours. Then I put some dirt around the base, to seal the air holes and slow the fire down, but I left the chimney open. The fire continued on, eventually slowing down after a couple more hours. Once I saw that it was nearly finished, I closed off the vents again and left it for the night.
Here's what I found this morning:
Beautiful, well formed charcoal. There were still some unfinished pieces, I set them aside. I could have let it go even longer, and converted those too. All told, I got a heaping 5 gal bucket full:
So now I know how to make this. I think I could keep us supplied with some charcoal for the smoker and the gasifier. It's not hard - I could scale up to bigger batches quite easily. But for now I'll take it one bucket at a time.