Gold & Silver Forum - Making Charcoal

Electric Amish had said he was interested in seeing my charcoal pit in another thread. I still don't have a decent camera. :no_ma: Anyway I figured others might be interested in the subject since charcoal is useful for so many things... cooking, filtering, heating, working metal, improving soil, etc.

I've tried a wide array of different charcoal making methods. The one I've found to be the most satisfactory is also probably the simplest. Somehow I'm not suprised. The basic technique is to build a large fire in a container or pit and when everything has combusted well, about a 50% reduction in mass or so, kill the oxygen supply. This process is obviously about 50% efficient, even using a retort I haven't yet managed to do much better than that. Well, that isn't entirely true... you can get a high degree of efficiency but you pay for it by ending up with more brown ends, wood that didn't turn to charcoal. Using a 55 gallon drum as a kiln it's a lot more worthwhile to me to lose half my wood pile and end up with 25 gallons of charcoal than to lose only 1/3 of the wood and get about 5 gallons of charcoal. It's a real pain to fish out unburned wood and start a new burn five times in a row to get the same ammount of charcoal.

There are a number of ways you could go about making a kiln. The first I tried was just a pit in the ground. I started a big fire, let it burn like mad and then covered it with dirt and watched it smoke for several days. I ended up putting in about three times as much wood into this fire as I got out in charcoal, not very efficient but it was a large burn so the total ammount of charcoal was also large. The biggest problem was getting it out of the dirt, a job I ended up having to do mostly with my own two hands. That's when I got the 55 gallon drums. Initially I wanted to build retorts that re-routed the woodgas to the fire to sustain the burn. It works but requires a lot of infrastructure and expense. Iron pipe isn't cheap these days, you need a frame to hold the barrel and you need insulation around the whole mess to get it hot enough to work. By the time I was done I was getting about 50% efficiency and the cost of the project was threatening to get high.

Burning in a container is more conventient for me than burning in an eathern pit because of that mixed in dirt I mentioned. The trouble with 55 gallon drums, or any steel really, is that the heat causes flaking and rust. Sooner or later you will burn through the drum, just like a cheap grill. I've got maybe 10 burns on one drum right now and it is starting to look bad, still solid though. I'd guess there is probably 20 to 30 more burns left in it.

I mostly want charcoal for agricultural purpose, to increase soil biodynamics and break up heavy clay. Obviously that means I have a lot of clay to work with and this has me thinking about an ultimate solution. Right now I'm looking at creating a clay kiln to burn the wood in. It won't rust out like the steel drums and it won't end up with too much dirt mixed in like the pit I was using. If thick enough it shouldn't crack for a long time and when it finally does the clay will have been fired enough times at a high enough temperature that its properties will have changed. When ground up instead of being sticky it should act more like sand.

As far as wood to use goes... try to keep to only one kind of wood in a given burn because of varying burn rates. Also try to stick to pieces of 3" diameter or less for better results. This will reduce the ammount of brown ends you'll have to deal with. If you are making charcoal for agricultural use rotten wood works great! It converts readily and it very easy to powder. You get the same bulk with rotten wood as you get with solid "fresh?" wood. Other things like grass clippings and pine needles will also work but it is in your interest to get them as compressed as possible before the burn or you'll lose a lot of combustion and the overall yield will be low due to air spaces. On the subject of air spaces, I have gotten the best results from laying the wood horizontally with the minimum ammount of air space between the pieces. Remember, a 55 gallon drum doesn't have 55 gallons of wood in it, it has maybe 40 gallons of wood and a lot of air.

Here are some charcoal making resources.

The Handbook of Charcoal Making

http://books.google.com/books?id=1jV...DFBqsw#PPR3,M1

Woodgas retort

http://www.twinoaksforge.com/BLADSMI...20CHARCOAL.htm

A satisfactory 55 gallon drum kiln

http://www.eaglequest.com/~bbq/charcoal/