Making Natural Charcoal

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Peanut

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Part 1

Years ago I started making charcoal to sell at the farmers market. The retort method I use is old and has been used for other purposes than charcoal. Most notably by Sir Henry Bessemer in making high quality steel.

It’s a simple method that anyone can master it but it is hot, hard work. Can’t get the components I use? With a little imagination all components can be changed or modified as long as simple principles are followed.

In the process I use small pieces of quality hardwood that are placed in a small 15-gallon steel drum. The small drum is placed into a larger 55-gallon steel drum. Scrap wood is then stacked in the gaps between the two barrels and burned. This “cooks” the quality wood into charcoal without allowing it to be consumed by fire.

Primary Components

Furnace – 55-gallon steel drum with removable lid, usually called an “Open Head”. The lid is held on with a nut and bolt closure ring or a quick lever closure ring (preferable). The lid is used during the process to help control the burn.

Retort – 15-gallon steel drum with removable lid. The crimp type lid is most common around here.

Both can be purchased new or obtained used from trucking companies or large farms etc. If only used drums are available I recommend oil or grease drums, then burn out the contents. I don’t feel safe using a small drum that might have held unknown chemicals or came from unknown sources.

Secondary Components/Tools

3 fire bricks or other spacers that won’t burn. These are used to keep the small drum off the bottom of the large drum. A brick is 2.25 inches thick, this distance has worked well for me.

You’ll need welding gloves and a heavy fire poker. I made one from rebar. You’ll also need 2 pieces of rebar to use as a spacer between the lid and furnace. I cut them about 30” long. Also needed, very large channel locks.

Wood: 2 types

Any quality hardwood makes great charcoal, various oaks, hickory’s, even maple. I experimented a lot the first year. The properties vary with the type of wood used. I prefer red oak over other types. It comes out very pitted with large cracks. It is easy to light and produces a very even burn when used for cooking. It’s also great for water filtration without enhancements.

Cut a red oak log and allow it to dry 9 months to a year. For making a batch cut discs, 5 inches long, off the end of a log. I used a vertical log splitter as much as possible. It worked great for splitting log disks into smaller pieces that can then be split with a hand axe.

In this step I used a hand axe and cut the wood into pieces about 2 inches X 2 inches X 5 inches. If the pieces are larger it just adds unnecessary cooking time.

Tip on tree selection – Pick a tree that grew among older trees at least 100 yards from any open area. It would have grown straight, tall and fast, with very few limbs. Great for splitting! A tree at the edge of a field gets more sun and will have had many more limbs as it grew.

Scrap wood. You’ll need tinder for starting the fire and some hardwood as it produces a steady even heat. Lastly, small amounts of scrap pine lumber. It’s cheap and easy to acquire. It produces quick heat, helpful in regulating the cooking process. All are split small enough to go in between the sides of the barrels and about 2 feet long.

Component Modifications

A. Furnace Drum

1. The removable lid is used to help regulate air flow during the cook. Most have 2" x ¾" Head Fitting Plug, also helpful with air control.

2. Cut horizontal vent openings along the side of the furnace drum at the bottom edge. Cut 3 vents, 2 to 3 inches high X 8 inches long. Space them evenly around the circumference. Leave one end attached so they can be partially closed or opened to control air flow during the cook.

B. Retort Drum

1. The retort drum bottom must be vented to allow gas to escape from the wood while it is being cooked. These gases leave the retort before coming into contact with oxygen and burn. This cuts down on the total amount of scrap wood used. When out gassing starts you will really be able to feel the extra heat coming from the furnace.

2. In the bottom of the retort drill 1/4 inch diameter holes, 25-30 is plenty. Space them evenly over the bottom. I didn’t measure, just eye-balled it.

Assembly

1. Put the fire bricks in the bottom of the furnace to support the retort. It allows space for out gassing but it also prevents the ground from wicking heat from the retort.

2. While loading the retort with wood, shake it as you go to settle it. This insures as much wood as possible is cooked per batch. It also leaves as little space as possible for oxygenated air. Put on the lid and clamp it tightly. Set it inside the furnace drum on the fire bricks.

Note: At some point early in the process there will be a flash burn in the retort. Its over quickly and leaves no oxygen in the retort, a good thing.

3. Drop kindling down the outer sides of the retort and then pack scrap wood around the sides and over the top.

4. Stuff paper and tinder into the furnace vents and fire it up!

Part 2 next
 
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Peanut

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Part 2

Cooking a Batch, Moisture is your enemy!

The goal is to hold at least 700 degrees in the retort for approximately 1.5 hours. Make sure the moisture content is low as possible in all the woods used. High moisture content will use up a more scrap wood and time. To start cooking I usually wait for a 10-12-day dry period, usually in August. I also cook in the afternoon, hottest part of the day. Dry air and the hot sun are your friends.

Use the lid of the furnace to hold heat in but not so much as to kill air flow. I raise the lid just a little with pieces of rebar between the drum and lid while cooking. I also start with the “Head Fitting Plug” removed. I hook the hole to make moving the lid easy. I remove the lid occasionally while adding wood and making sure scrap is burning evenly.

As the burn progresses ash and coals will drop to the bottom of the furnace. It will start to clog the 3 vents, keep the vents clear for good air flow.

When the batch is done attach the lid to the furnace and tighten the band. Screw in the “Head Fitting Plug”. Close the bottom vents on the furnace and cover them with dirt to stop all air flow.

Tip – Don’t allow the scrap to burn out naturally. When you decide the charcoal is done seal the furnace. The burning scrap in the drum will use up remaining oxygen and help prevent charcoal loss.

Leave the air tight furnace to cool over night. If you expose the charcoal to oxygen while it is still hot it will ignite and burn up all your work. I remove the retort the next morning. It should weigh about 22/23 lbs, if it feels a lot heavier you did not get a complete conversion.

Pour the contents onto a framed 1/4-inch screen to filter the tiny pieces and dust then bag your charcoal. You should have about 18lbs of high-quality natural charcoal.

You have to learn to read the smoke. There is an art to this!

The first smoke will be heavy and white. This is moisture from the scrap wood and will continue for a while, then almost disappear. A short time later the white smoke will reappear but not so heavy as before. This is the moisture/steam from the wood in the retort. The conversion process is underway.

Tip – On days with higher humidity or if the wood in the retort has a higher than normal moisture content… The time from when the fire is first started to the time the retort finishes producing white smoke will be longer than normal. This is an indicator that the time for the conversion to be complete will also be longer. Meaning you’ll have to cook the retort longer. This is something only experience teaches.

Don’t worry too much, the odds are at some point you’ll go out the next morning and find a partially converted batch. You’ll have to clean out the furnace, prep scrap, reload and re-cook the same batch again, an invaluable lesson.

Sometimes there is a small amount of charcoal loss to fire, usually just on the surface of a few pieces at the bottom of the retort. A lot of ash is caused from not having the lid on the retort tight enough. Do not allow air to flow through the retort!

Although crude this is a very effective process for producing high quality natural charcoal. I normally run 2 furnaces at the same time and can produce about 35 pounds a day.

One person can prepare all the oak and scrap for 2 furnaces and have time to cook both batches concurrently in one day. Cooking with 2 furnaces has advantages. They will share radiant heat cutting down on the total amount of scrap used. I place them within 3 feet of each other.

When out gassing begins the temperatures will jump to near 1000 degrees. Metal will begin to soften. It’s difficult to feed and work the furnaces at these temps. Be Quick and Be Careful!

Only cook in hot weather, 90 plus degrees and sunny with low humidity. If the temp is around 70 you will use a lot more scrap to cook the same batch, more work and time for the same return.

I only use seasoned red oak for charcoal. Wood from things like pallets could have been treated or had chemicals spilled on them and should be avoided. I use some of my charcoal for medicine and water filtration, no point in starting with contaminated wood.

You’ll get 20 batches or so out of a set of barrels. They will deteriorate over time from high heat.

Tip – one last tip on out gassing. Once by accident I was still cooking after the sundown. Out of curiosity I looked through a vent. From the holes in the bottom of the retort jets of blue flame could be seen. This can’t be seen in bright sunlight. There after I timed a cook so the out gassing was complete after 5pm. When I wanted to check if the out gassing was near completion, I place an object to cast a shadow and take a quick look through a vent. This allowed me to know exactly when to seal the furnace. No blue flames mean out gassing is complete.

As preppers being able to make your own charcoal is a handy skill to have. As I wrote at the start the components I use can be changed or modified. Around the country average humidity varies greatly as do the available wood species. At best the process I used is nothing more than a general guide for others to reference. Use your imagination and make some great charcoal!

Pics...
FC 01 – Stacked red oak disc’s ready for processing.

FC 02 & 03 – red oak split into bricks with a log splitter. The radiator isn't attached, it was there to divert exhaust from the engine.

FC 04 – Loading the retorts

FC 05 & 06 – Barrels ready for cooking

FC 07 – Scrap pine I got from a local wood products company. It’s already in small pieces, ready to drop into the barrels. Quick burning pine is helpful in regulating the cooking process but scrap hardwood provides most of the heat.

FC 08 – Vent holes in the retort.

FC 09 – 1 of 3 vents cut into bottom edge of a large barrel.

FC 10 – About 5lbs or the finished product

Farm Charcoal (01)a.jpgFarm Charcoal (02)a.jpgFarm Charcoal (03)a.jpgFarm Charcoal (04)a.jpgFarm Charcoal (05)a.jpgFarm Charcoal (06)a.jpgFarm Charcoal (07)a.jpgFarm Charcoal (08)a.jpgFarm Charcoal (09)a.jpgFarm Charcoal (11)a.jpg
 
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Grizzleyette___Adams

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Thank you so much for reposting this here! I remember reading this some time ago and lost track of it. So glad to have it right here at home, in homesteadingforum.org!

I must do this!


.
 

Peanut

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I posted this at 3 or 4 websites years ago. I noticed recently that only 2 still existed. The only one with photos required membership.

So I thought I should post it here. I spent a few days rewriting the process, reworking some of the photos.

One more note... the scrap pine I used came from a small wood products company in a little town close to me. They made wooden railing parts for decks. The cut off and discarded ends of the balusters were the perfect size for my process, about 2"x2", assorted lengths.

Anyway, knowing places that might have wood scrap saves a lot of work.

Sort of funny, when I asked the owner about the scrap pine I traded 10lbs of charcoal for the first pickup load. Soon, all his employees were buying charcoal from me!
 
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Biggkidd

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Thank you nicely done. I wonder for a longer term setup if stainless steel or iron wouldn't burnout so fast? I think it's the carbon in steel that makes it burn up and flake apart like it does. Curious what does a bag of charcoal sell for? I haven't bought any in about a dozen years as I grill over hardwoods.
 

Peanut

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Natural or "Lump" Charcoal is sold by places like L o-w e s. I've even seen lump at walleys. There is a range in quality. The big appliance store has the better brands of the two.

That said, none of them are in the same league as what I can make.
 

SheepDog

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The types of wood for making charcoal depends on its ultimate purpose. For use as fuel the hardwood charcoal is tops but if you are making charcoal for art (drawing charcoal) or for making black powder you need different wood. The best for drawing charcoal is sprigs of willow and for black powder you should use first and second year growth willow. The sprigs of charcoal can be used as they come out of the retort but the charcoal for black powder has to be run through a ball mill to get it to the fine powder needed to combine well with the other chemicals.
The charcoal made from hard woods will never powder fine enough for black powder and is too porous for good art use.
 

joel

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Peanut, I like your way better, but this is how they did it in the olden days:
 

Peanut

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Thanks @joel, your post reminded me. Mike Rowe did a Dirty Jobs episode at a charcoal factory in Missouri. I just looked it up...

episode 15 in season 6 "Micro-Algae Man" November 1, 2005
"Pet groomer, micro-algae man, charcoal maker (lump charcoal factory)"

It was filmed at the Struemph's Charcoal Works in Steelville, Missouri. I couldn't find a video of it. Maybe one of our youtub watchers will know how to find it.

Sadly, Royal Oak bought out the company according to the net. Now the "Fire King" brand of charcoal is a mix of south american charcoal... sub-par, maybe they can use it in art class.

I found the following website that reviewed Fire King charcoal which was highly rated before being bought out. It has photo's. Just one look at the photo's and you'll see that my method produces far superior charcoal. But it is hot, hard work no matter who does it.

 
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Peanut

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Here is a pdf on making charcoal. It's uses the retort method but is a little different than how I did it. Who knows, if I'd have found this before I started I might have tried it this way. It does have some advantages.

I posted my method in the a permaculture forum in 2012. It's still there. Anyway, the guy who made this pdf was also a member. He and I compared notes in messages.

He was just experimenting and only made a couple of batches. His cinderblock structure wouldn't have stood up to producing charcoal on a regular basis. His barrel modification for out gassing was better than what I did. My method wouldn't have worked for barrels laying on their sides.

We both used steel drums with a limited service life. I still wonder about how well a steel barrel would stand up to constant cooking while on it's side. I don't think his barrels were supported well enough, once temps get close to 1000 degrees metal begins to soften. I see bad things happening to his barrels if he continued without changes.

His method produced a lot more charcoal on a single burn but he had several people helping. He was loading 2-55gallon retorts where I was loading 2-15gallon retorts. He wasn't using hardwood, just pine but I see no reason hardwood couldn't be used in this setup.

He also had an issue of some wood not being fully converted. I don't think he was burning long enough but can't say for sure. There is a possibility it was the way he positioned his barrels in the structure. The only way to rule out that possibility is experimentation which I couldn't do and he no longer did.

If you have help and can build a better structure, by all means use this method if you want to produce a lot more charcoal per burn. In a world apocalypse where I needed to produce large amounts of charcoal I'll improve this design. For example there needs to be a way to add fuel during the burn. His design is lock and load, no way to add fuel if for some reason you need to burn longer.

My method can be expanded but it'd become exponentially more difficult to control the burn with each barrel added.
 

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