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Help with Easy Biochar drum  RSS feed

 
Posts: 184
Location: Huntsville Alabama (North Alabama)
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I found the metal drum, used to hold Lime Juice. I also have the flue.  

I want to follow the easy method mentioned by Dr. Redhawk.

12 to 14 holes where the flue will be pop-riveted over.

Will this require any holes at the bottom of the drum? Any on the sides?
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You need holes around the bottom.  I make them with a hammer and chisel, so mine are more like big slits :)  As the wood burns down, keep checking the holes.  When you see the fire has burned down to the bottom near any one hole, kick dirt over that hole so the fire stops on that side.

I personally have the best luck using another complete barrel for a chimney.  I start the fire at the top of the bottom barrel and then put another barrel on top of the first for a chimney.  The chimney barrel also has holes around the bottom.  Once the fire has burned down to the holes at the bottom of the barrel full of wood and you have kicked dirt over all those holes, knock the chimney barrel off and put a lid on the barrel full of charcoal, or quench it with water.

They are several very attractive opportunities for burning yourself here, so please proceed with all due caution :)
 
Dennis Bangham
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I drilled 14 holes in the top and 16 holes in the very bottom side of the barrel.  Dug a large pit and found it has a clay bottom.  I am using a failed mushroom log experiment to fill the barrel and also create the fire underneath.
Will find out tomorrow or next weekend how well it works.
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If you end up not liking your drum consider the open pit method.  Since using an open pit I've realized that I will never go back to a drum....too little production and just another ugly thing taking away from having a permaculture paradise.  I was very happy when I got rid of mine....although I do singe myself sometimes with an open flame (will add a large stone or other surface to draft the flame and act as a chimney to take care of that issue).  Best wishes.
 
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Please take a look a the various videos on youtube of the "Cone Kiln" designs.



I have used barrels for making both charcoal and biochar and would never go back to that again. The batch size and yields are so small, and the whole principle is working against the fire, rather than with it.

  • In the cone kiln the base is completely sealed and the top is completely open.
  • Dry fuel is added to the kiln and the TOP is lit. The flames above the fuel protect the wood from being burned away, because they are in a low oxygen environment, while simultaneously burning the gases above hot and clean.
  • More fuel is added in layers, and as it chars it collapses down in to the bottom of the kiln where it totally stops burning.


  • This is the total opposite of my experience using drums, where the air is added at the bottom. In those designs you are continually fighting a balance between just enough air to get it to ensure proper combustion, but not so much air that your wood burns away to ash. It was smokey, and tricky to control, and depended on having dry materials of small enough dimensions to fit in the drum.

    I wanted to experiment with the cone method, but didn't have the funds to splash out on fancy metal kiln. I adapted the technique to a trench, and was very very happy with the results.

    Biochar Trench Method
     
    Greg Martin
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    Yes, the cone kiln and the open pit/trench are essentially the same, except that you don't have to buy a metal object and have it shipped.  The in-place trench method is perhaps the best if the land is open, not already a food forest.  Clearing dropped branches in the fall in a trench that will become a planting bed in the spring is pretty attractive.  A great mimic of a forest fire disturbance.  Composting in place with that spot would make it even better.  Anyone who has not composted with biochar in the raw materials mix is missing out.  It's the most beautiful compost you'll lay your eyes on!
     
    Dennis Bangham
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    Thanks for the inputs. I hope this will help limit the smoke and flaming ashes.  

    My problem is I live in a neighborhood with restrictions on open fires.  They allow metal fire pits since they can contain the fire and flaming ashes.  

    I located this to a back area of my yard and will only use when the ground is wet and since my lot is only 0.65 acres I should not need to use more than 2 x a year.  I can always fall back to using the pit I dug too.
     
    Trace Oswald
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    My own experience is different than others here. I started making charcoal in a barrel,  went to a retort,  tried the pit method,  and then went back to a retort. I get the best charcoal from a retort. With the barrel I get too many brands and it's hard to tell when a batch is done.  With the pit,  it's easy to get brands as well as burning a lot of wood to ash,  and I don't like shoveling the charcoal out,  sorting the brands and putting them back in to burn again.  With a retort, I don't have to quench the charcoal when it's done,  and I prefer working with it dry. I suspect which method a person likes is largely personal preference and situation more than because one method is "better", so I wouldn't be bothered by the fact that your situation lends itself to one method over the others.
     
    master pollinator
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    Is it possible to alter a drum to function like the deep cone kiln?

    What would happen if a metal basket or grate was placed in the drum, reaching about halfway down, such that the pile would burn in a similar way? The pile would burn at the top, creating an updraft around the barrel, keeping the bottom of the pile and anything falling through the grating in an oxygen-free environment. It would burn from the top, coals would settle and drop through the grate, and you keep adding material until the barrel is chock-full of charcoal.

    And it quenches itself, in an oxygen-deprived manner, so less monitoring of the burn status is necessary, and probably more uniform pieces at a similar state of pyrolysis.

    I think short of a giant retort that you could load large pieces in, the cone kiln is probably the best idea I have seen so far, and should meet most burn appliance ordinances.

    But if you like what you're doing and you're getting good results, good job. You might be able to tweak your approach for better efficiency or higher biomass to charcoal conversion rate, but don't let the perfect be the enemy of the good.

    Keep it up, keep us posted, and good luck!

    -CK
     
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    I was considering many processes.  I tried this one because it seemed to make the most sense.  A pit makes too much smoke and doesn't burn the wood vertically, so it's not efficient.  The retort creates tiny amounts of biochar.  I knew I could get a 55 gallon drum cheaply-for free in fact.  I got the chimney at the Habitat for Humanity restore for $1.  This video seemed to work really well for me except measuring the top. Easier just to center it with your chimney by hand drawing and go.  The only other thing is knowing when to quench the fire. I learned from trial and error-easy.  Just wait until the flames die down to the height or just above the biochar.  

    https://www.youtube.com/watch?v=YIbGkmt1VdE

    John S
    PDX OR
     
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    This spring me and a friend made the "tin-man" by Bob Wells from living web farm, because that man seemed the most dedicated bio char maker i found. Have only used it one time as a try-out, still waiting for the paint to fall off. I gathered you need very dry wood as well for a perfect batch 600 degrees burn. The higher i stacked the chimney, the more pull, the less smoke.
    How did your bio char turn out Dennis?
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    Michael Cox
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    John Saltveit wrote:A pit makes too much smoke and doesn't burn the wood vertically, so it's not efficient.



    That is the exact opposite of my experience with a trench method. I wonder if it is to do with how the fire is constructed, lit and fed?

    I fill my trench with dry branches as an initial charge, then put a layer of thinner kindling size twigs over the top.  I then light the kindling layer on top, which burns hot and fast, because it is dry and has excellent air circulation, being propped up on the branches beneath. As it burns it cooks the wood beneath it, and the smoke from the layer below passes up THROUGH the hottest bit of the fire and burns off completely. The embers from the burning layers above fall down through the wood beneath so the burn front spreads downwards into the pit with little to no smoke. Once it has burned down to a good layer of embers I start adding more material above, allowing each layer to get going properly before adding the next, so there is still little to no smoke.

    By the time I'm done I have a trench full of char.

    On the other hand, many people build a bonfire, then try to light the bottom of it. The embers fall down and away from the remaining fuel (less direct heating) and the smoke from the partially cooked fuel rises up and away from the combustion zone.
     
    Greg Martin
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    John Saltveit wrote: A pit makes too much smoke and doesn't burn the wood vertically, so it's not efficient.



    I hope my experience can be helpful to some folks who come across this.  My experience is that a pit can be near perfectly efficient and smoke free.  For example, my pit makes 200 gallons of biochar per batch from about 400 gallons of starting wood, which is the volume reduction that I get in a kiln where none of the biochar is lost.  Also it only generates a little smoke when I'm first lighting the fire.  After that there is virtually no smoke as the hot fire burns it all up.  I add the wood so as to create a teepee structure.  Perhaps that helps as the wood is not laying horizontal but rather is funneling the pyrolysis gases to the center.  Even with generating a cubic yard at a time I find I always need more, so a smaller system wouldn't work for me.  If anything I'm thinking about scaling up the pit to make several cubic yards at a time.
     
    Greg Martin
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    Looks like we were typing at the same time Michael!  How much biochar volume can you produce in your trench at a time?  I've been thinking of trying the trench geometry to allow for the use of longer wood and I'm wondering how large a single person can go before it's hard to manage the fire without losses.  Thank you for sharing this!
     
    Greg Martin
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    Also, I like the trench geometry for creating biochar at the site of a future planting, just did the dirt back in to make a sort of biochar version of a hugel….it's on my bucket list of things to experiment with :)
     
    Michael Cox
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    Greg Martin wrote:Looks like we were typing at the same time Michael!  How much biochar volume can you produce in your trench at a time?  I've been thinking of trying the trench geometry to allow for the use of longer wood and I'm wondering how large a single person can go before it's hard to manage the fire without losses.  Thank you for sharing this!



    My trench was about 8ft long, and I was burning pieces up to about 14ft max. You just have to occasionally go back and chuck the unburned ends back in. I didn't care too much about losses as I had a HUGE amount of thinnings to process - it was more about getting it done quickly, with minimal processing steps. I was about to take whole sapling stems (up to 14ft long, some 6 inch diameter) and just lay them on, parallel to each other.

    Periodically I let the fire burn down, and too a shovel and emptied the trench into a tub of water. This worked well as the trench itself stayed hot enough that I could carry on loading straight away. I was able to burn for a whole day.
     
    John Saltveit
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    Greg,
    The tepee structure makes sense as it can make it more vertical, like a rocket mass heater, and thus more efficient. That is not what I've seen from most pits.

    An important point that you guys are making is the scale.  My 55 gallon drum fits the extra prunings from my .2 acre food forest really well. I am currently running about 4 loads of it per year.   I don't have room for a pit in the yard.  I can burn the drum in the driveway, so I don't endanger anything nearby.  The 55 gallon drum and chimney are skinny and vertical, taking up very little space.  I use the drum to put wood into it during this time of year, so it is storing the wood to dry it out, which I couldn't do with a pit.   It sounds like you have bigger yards and more wood or biomass to get rid of.  

    I like how we are presenting a wide variety of options for people who have different situations.

    JohN S
    PDX OR
     
    Michael Cox
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    John Saltveit wrote:
    The tepee structure makes sense as it can make it more vertical, like a rocket mass heater, and thus more efficient. That is not what I've seen from most pits.



    Efficient in what sense? A rocket mass heater is very efficient at ensuring complete combustion of the fuel, because the draft blasts through the burn zone with loads of oxygen. It is very hot and clean, but doesn't seem compatible with a system that focuses on collecting char. The ideal burn from my point of view is one where NO air gets to the base of the fire, and the fuel packs as flat and dense as possible. Then above that zone I have a hot a clean combustion zone of pyrolysis gases. The flame front should protect the char that is collecting, otherwise you are promoting complete combustion of the char.

    From personal experience I hate the tepee structure for fires in general. It seems nearly inevitable that the inner core burns out quickly, and drops away from the outer layers. The outer layers are self supporting, so don't drop down as the charring wood beneath collapses, so end up further from the combustion zone. Then you end up with a smokey fire, and more wood that burns away completely. I'm sure you can work around this - drier wood that chars faster would help, as would cutting to shorter lengths, and more careful management of loading - but it is much more work than simply laying whole stems horizontal along a trench.
     
    Greg Martin
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    Michael Cox wrote:From personal experience I hate the tepee structure for fires in general. It seems nearly inevitable that the inner core burns out quickly, and drops away from the outer layers. The outer layers are self supporting, so don't drop down as the charring wood beneath collapses, so end up further from the combustion zone. Then you end up with a smokey fire, and more wood that burns away completely. I'm sure you can work around this - drier wood that chars faster would help, as would cutting to shorter lengths, and more careful management of loading - but it is much more work than simply laying whole stems horizontal along a trench.



    You're guesses are correct.  When I clean up my wood I cut it to 2' lengths and stack it to dry completely before charring.  I then start with small diameter wood, move to the largest and then move back to small again at the end to ensure I maintain a flame cap while converting all the wood.  I think John was suggesting that it is very efficient at burning all the smoke to maintain clean emissions throughout the burn while very efficiently converting the wood to biochar, which it does very well.  Michael, you are also correct that this method involves extra work doing all that cutting (and if the diameters are too large then splitting as well).  I'm ok with the extra work for the high carbon capture aspect, though doing less work and achieving the same is much better!


    John, you're also right about the size of my property.  It's about 12 acres and I also bring home a lot of pine that line crews leave on the side of the road when they're clearing power lines.  Others will take home the hardwood for their stoves, but they leave the softwood to rot and release most of it's carbon.  I like that I can offset my driving with the logs I bring home and char.
     
    Posts: 14
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    Hallo,
    I have a large ammout of prunned vines from my vineyard every winter.. I have chopped them on garden electric garden chipper till now, but since I already have another regular source of large ammount of woodchips, I decided to turn the prunned vines into biochar by using 55 gallon barrel with a sparse grate in the middle (see Picture). Vines will be combusted in the upper part of the barrel, after turning into char they will spontaneously broke into smaller pieces and fall through sparse grate down into the anaerobic (oxygen-free) zone and burn out without changing into the ash.. I suppose this could work. I don´t have room enough to dig a trench/pit. What do you think?
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    Chris Kott
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    That is literally and exactly what I suggested in my post above. Thanks for posting that, Jan.

    -CK
     
    Dennis Bangham
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    I am thinking that a cone kiln or kon tiki design done into a pit would work.  Dig a deep pit and line with lightweight concrete.  Put some metal angle pieces half way up and make a rebar screen to hold the fire.  This will let the char drop down and be smothered by lack of oxygen.

    This could be done in any backyard.  Cover with a tarp when not in use.  Should last years.  

    would need to find a heavy duty and fine screen dome to keep the sparks down and this should meet city ordinances as a "Fire Pit".
     
    John Saltveit
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    This is a great discussion!

    You guys are really helping me visualize what we're trying to do here, and at what scale.  Yes, Greg/Michael, that is what I meant.  The efficiency that I'm looking for is relatively large amounts of high quality char and low smoke. That's what I've been getting. The flame goes very high up into the chimney, and burns the volatile gases.   There is no air that can come in from the sides.   The char is very light weight, and makes a musical tone when it hits something.  I do try to make the wood super dry for that reason, and I try to cut them into approximately equal lengths.  I have learned over time that I don't want unburned wood and I don't want ash at the end.  By timing it just as the flames die down almost to the char, it turns out really well each time.

    Great collaboration on the design and visual, Jan and Chris.  When I visualized a cone, I didn't get it. When it looks like a cylinder it makes much more sense to me.
    John S
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    Michael Cox
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    Jan  - That is a neat design for tidying up small diameter stuff. I visited a vineyard once where they burned the prunings. But they had made a funky fire-barrow - they had adapted a wheel barrow base with half an oil drum and long handles. They could wheel the drum down the rows while they were pruning and chuck the stems straight in to burn. It didn't catch char like yours, but it could have.
     
    Michael Cox
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    Chris Kott wrote:That is literally and exactly what I suggested in my post above. Thanks for posting that, Jan.

    -CK



    A picture worth a thousand words!
     
    Jan Hrbek
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    Michael Cox wrote:Jan  - That is a neat design for tidying up small diameter stuff. I visited a vineyard once where they burned the prunings. But they had made a funky fire-barrow - they had adapted a wheel barrow base with half an oil drum and long handles. They could wheel the drum down the rows while they were pruning and chuck the stems straight in to burn. It didn't catch char like yours, but it could have.



    Yes Michael, this is a quite common way of on-site burning vine prunings.. The bottom of the drum / wheelbarrow is perforated, so the ash continuously falls on the ground.. So - at least- minerals get back to the soil (if water or wind doesn´t carry the ash away..) But making a biochar (or woodchips) is a better solution how to "recycle" the prunings.. I think, that grapevine is quite good permaculture plant, because it produces a lot of biological by-products (prunings, pomace..) which can be used for emendation of the vineyard soil..
     
    Greg Martin
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    Jan, I think that idea makes a lot of sense and I tried it once, but I ended up getting lots of only partially charred bits in the lower portion below the grate.  I'm not saying that won't work as I've only tried it once.  It may be just a matter of playing around with the design and process to get it working perfectly.  Perhaps I was just using too small diameter wood which allowed it to burn through in places and then the uncharred portions fell through.  Maybe a critical smallest diameter needs to be figured out?  If you experiment more with this please post on your results.  I think a lot of people would find this useful.  Thank you.
     
    Jan Hrbek
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    Thank you Greg, I will try and let you know. The vine prunings are max 1 cm (1/2 inch) in diameter ad 50-100 cm (1,5-3 feet) long. So it depends on diameter of the holes in the grate, in what stage of burning will the combusted vines brake and fall through.. Better not to be charred enough than too much.. The char will be mixed with horse manure, grass clippings and leaves and inoculated by red worms or used in a mix with woodchips as a bedding in the chicken coop..
     
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