Making Charcoal

Charcoal. It’s handy stuff. Lights easy, burns clean, burns hot, easy to make. What’s not to like? Wait, easy to make? Yes! And I’m about to tell you how.
But first, some background. I promise I’ll keep it short.
I’m assuming you already have a basic knowledge about what charcoal is and what you can use it for (besides grilling burgers), and why lump charcoal is far superior to briquettes.
This is my current process. Actually, it’s 4 or 5 steps into an iterative process, eliminating methods along the way that are too complex, too inefficient or too expensive. Its silly if you’re spending $50 to make $30 worth of charcoal, spending hours digging & covering pits, or your process requires hard-to-find materials (like a 30-gallon metal drum). This is my current balance between ease, cost, and availability of materials that virtually anyone can do.
And of course the obligatory warning: This obviously involves fire. You may burn yourself, your property, your house, or that one dumbass chicken who’s always getting into trouble. This is how I do it and you’re on your own if you’re going to copy my brainless stunts. If you want my actual advice, just go to your local store and buy a bag of charcoal.
There, see? Short. Now on to the good stuff:

Materials

  • Charcoal wood – The wood you will be turning into charcoal. The precise species and shape (limbs, crotches, knots, solid wood flooring scraps, etc) is not that important, but keep the following in mind:
    • Needs to be cut into smaller chunks. The smaller the pieces, the quicker it will cook, but too small and you end up with crumbly bits (which is perfect for smelting iron or adding to your soil)
    • Dense hardwood is best – Maple, cherry, oak, beech, etc. Every once in a while you’ll find a dense hardwood (like locust) that almost turns into carbon lace. Enjoy the exploration!
    • Avoid composites, plywood, and pine or other softwoods (see “fire wood”).
    • Wood should be absolutely as dry as possible. Do not use green wood.
  • Fire wood – Anything that will burn, ideally cut into smaller pieces that can fit between the retort and heat shield
  • The Heat Shield: 50-gallon drum
  • The Retort: 6-gallon metal bucket with tight lid. Honestly any metal bucket, barrel, or drum will do as long as it has a tight top. A 30-gallon drum with a removable lid is actually ideal for fitting inside a 50-gallon drum but these things are rarer than hens’ teeth, kind of expensive, and the retort is inherently expendable and will wear out over time.
  • Bricks: Just clay bricks. Can even be broken. Avoid concrete “bricks”, they will degrade very quickly in the fire.
  • A firepit

Construction

The Retort:
Drill a hole in the bucket lid, about 3/8. You can drill more than one; I find one is best, though its probably not that important.
The important thing is that you only want holes in the lid. The principle is that the heat cooks the wood inside the retort and releases the volatiles that escape out the hole in the lid. Since there’s no way for oxygen to get in (since there’s only one hole and the volatiles are escaping through it), the wood won’t burn, and turns into charcoal.
If there is a hole anywhere other than the lid, then there is a way for oxygen to get into the retort and the wood will start burning. Note that the lid doesn’t have to seal completely airtight, just mostlytight, as long as there aren’t any holes in the bucket body itself.
The Heat Shield:
Cut the top and bottom off the 50-gallon drum. Keep the rolled lip, it will help reinforce the drum.
The Fire Pit:
If you don’t already have one, or know how to make one, stop reading this now and go educate yourself before you end up in the burn unit.
That’s all! Let’s make some charcoal!

Setup

Load your charcoal wood into the retort. You can pack it in there pretty tight, just leave some space around the individual pieces for the gasses to circulate. Give the lid a few good thumps to make sure it’s tight on there.
Place your bricks around your firepit so that you can put the 50-gallon drum over your fire and keep the bottom off the ground (for air circulation)

Making Charcoal

Now the fun part!
Light your fire. Make it strong but not so big that you can’t get the 50-gallon drum over it. This is a good opportunity for your family to enjoy a nice fire and cook some hot dogs, roast marshmallows or whatever. You can get down to business once everyone’s done having fun.
Then put the 50-gallon drum over it. Toss a couple pieces of wood in there to keep it going and build up a good bed of coals.
Once you have a strong bed of coals, lower the retort down into the drum, onto the fire. BE CAREFUL! YOU ARE REACHING INTO A FIRE! Use tools, welding gloves, or whatever other thing you need to keep your friends from laughing at your burn scars. Make sure your retort is stable. The last thing you want is for your retort to be perched on a log that collapses and tips the whole thing over, sending red hot metal and burning logs rolling down your hill. Trust me on this one.
Now, toss some more logs into the drum. Ideally you want skinnier logs that will fit between the wall of the drum and the retort.
What you’ve now built is a giant rocket stove with your retort in the middle. If you have a good bed of coals, the fire should take off pretty quickly and it will burn hot and clean. Soon you should see a plume of smoke coming out of the hole(s) in the retort lid, and when the fire gets big and hot enough, that plume of smoke will turn into a jet of fire and start to roar like a itty bitty jet engine.
This will go on for a while. Keep feeding logs into the top of the drum. Keep an eye on the retort and make sure it doesn’t tip over or lose its lid. Eventually, that jet on the retort lid will stop, and then you know that you have cooked off all the volatiles and your retort is full of charcoal. The time this takes will vary widely depending on the density of wood, how tightly packed the retort is, how hot the fire is, and how much moisture is in the wood.
Once the jet (or smoke) stops, just let the fire burn down. Don’t add more wood. I’ll leave it up to your judgement and safety threshold as to whether you want to bank the fire, get out the hose, or something in between.
Whatever you do, DO NOT open the retort. If you pick it up, you will see how light its gotten and just be dying to pop it open and see. Don’t. That charcoal inside may be hot enough to catch fire and the only reason it hasn’t is because there’s no oxygen. Guess what happens when you open it? I repeat: DO NOT OPEN THE RETORT. Put it aside and wait until tomorrow.

The Next Day

Once your retort has cooled (probably the next morning), then feel free to open it up. Congratulations! If you did it right, you now have a 6-gallon bucket full of high-quality lump charcoal. You will see that bucket is A LOT lighter, and maybe only 2/3 as full as it was when you started. This is normal. Be absolutely sure it’s cooled off, and add it to your stockpile of charcoal.
If your charcoal hasn’t cooled off, there’s a real chance that once you remove the lid and expose it to oxygen, it will catch fire. Remember, this is lump charcoal, not briquette, and it catches fire extra easy and burns without smoke or flame and often with very little ash. Toss one tiny ember in your charcoal stockpile and you’ll lose all of it.
You may well find a number of pieces of wood that are not fully converted to charcoal and are still normal wood or somewhere in between. This is normal. Just keep those to the side and toss them in for the next batch.
If you remove the lid and find a bucket that’s full of ashes and a lot less charcoal than you’d expect…And you have an air leak somewhere. Instead of cooking into charcoal, oxygen was getting in somehow and burning your wood inside the retort.

Well, that’s it. Enjoy, and be safe!

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