Gardening & Wildlife


My first attempts at making biochar were rubbish. I took the knowledge I had of traditional practice and tried to recreate it on a small scale using a barrel method. In fact, it would only be time when I would discover the key to success after seeing how they made biochar on MyFarm, a charitable organisation I stayed with over a period of 3 years. But that was not the first time I saw its successful production. I remember them clearing the Rhododendron-infested lands of Hill Holt Woods in Nottingham and owning a giant metal container, converting weed-wood into saleable charcoal. Of course, this type of wood would not be as calorific as say, English deciduous, because deciduous wood is more dense. Hence, when you look at the traditional practice in Europe the whole process requires a lot more heat to be able to penetrate the wood without incinerating it. As such charcoal is tradiitioanally made over a number of days under large earth mounds in which wood is tightly packed on the inside and then covered in earth to ensure that, as it burns inside-out over 3 days, it collapses in on itself whilst any flames are dowsed by the actual soil. Air vents are want to open up, in which case these must be covered during the process. Ironically, the first time I saw this process being used is when I crossed the border of Senegal to The Gambia and the army accosted me and showed me around the grounds. Living in relative poverty it was one of the main activities outside military training.


At MyFarm, in the Gambia, I saw the version I wanted to recreate. There, a smaller barrel completely pocked with holes, was placed inside a larger barrel that had a lid and flu. The whole process took less than 2 hours. Finely chopped material was inserted in the small barrel and placed inside the larger one slightly raised off the base. Around the small barrel in a space no more than 6inches wide was stuffed the combustible material over and around. The lid and flu was then placed on top and a flame thrown into it. Within a minute or two the whole was burning outside-in. As the flu drew the flame up drawing cold air in through the bottom the temperature began to rise and the flu sealed to allow the wood to gasify. The only down-point to this whole process was that it was labour-intensive in its preparation stages cutting the material up. This speeds up the burning process but only creates mainly fine charcoal processed later into compressed fire blocks. Having been unable to source 2 barrels of the correct size difference I instead invented my own method.


My first method was a combination of these 2 African models I had actually witnessed. I took an open-ended barrel, filled it with wood, lit a fire inside it and inverted it onto bricks. I then covered up to half its height the whole thing in sand, and wished for the best. As you can imagine hardly anything had burned.


My next attempts were more calculated. I read a pamphlet and decided to make a lot more air holes whilst ensuring the lid was quite snug; it didn't need to be tight. I started making proper charcoal but it took too much time and the quality of the burn was inefficient. There was obviously a knack. A good burn requires dry wood else it will never really get going. Secondly, the quality of the wood alters the burn times. Thin wood disappears very quickly, and if the wood is too thick it doesn't burn through. Depending on your resources and climate burning times will naturally vary. Over 2 years I modified the process and came up, with what I think, is the best method. The key was to insulate the barrel, and for this I used another double open-ended barrel cut down its length so that it opened like a glove. Placing this around the burn-barrel I held it in place with wire. It worked a treat.


No wood is wasted on the land in sunny Catalonia. I have 3 main sources from the farm, the cuttings of carob, olive, and pine. They all burn differently so I got to know how to mix it up over time. Olive wood gasifies and raises the temperature. Beyond the thickness of a cricket bat it is better left to dry and used as firewood, or building material. Carob prunings are so rotten that I use them towards the end of the burn. Freshly-cut pine is best used thickly to add bulk to the end product. By looking at the photos you should be able to learn to optimize your own methods. Here is a list of the whole process broken down.

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  • 6.


    Take an open-ended barrel with 2 sets of 1inch circumferal air holes along the base and middle points with its insulating barrel held around it by strong wire

  • Ensure the rough-cut lid can be fixed in place by a wire brace when the barrels are inverted
  • Jam-pack it full of highly combustible material of a wand-type nature (I use olive for its high-oil content)
  • Ensure it is sticking out of the barrel by at least another half-length
  • Ram into this mass thick straight pine branches, no higher than the level of the lid, that have been cleaned up of excess and are a little drier in order to get the fire going at first
  • Create a dais using 2 short trunk sections for the barrel to stand upon afterward. Ensure you have enough sand to hand for the last part of the process
  • Start a fire on top and add any old scrub to create an inferno
  • Keep adding until you see glowing coals at the bottom of the barrel through the air holes, occasionally shaking the barrels to help material down to the base
  • Top up the barrel with thicker stubby material (I use rotten carob wood) to the level of the lid. The flames will naturally begin to dowse themelves through a lack of oxygen
  • At this stage there is a lot of smoke, so wear your protective equipment
  • Place the rough-cut lid onto the smoking mass and brace in place with a diametrical wire pierced through the barrel. It is not ideal to have a tight-fitting lid
  • Invert the barrel 180 degrees so that all the weight of the material falls onto the lid
  • Manouevre the very hot barrel on top of the dais positioned in such a way as to allow 2 air-holes either side
  • Pile up a load of sand around the base allowing some air to enter at first
  • Occasionally shake the barrel down and completely exclude any more air gaps at the base
  • Leave for up to 4-6 hours (A keen experienced eye is key. I prefer doing it in the night but you will need a torch light)
  • Invert the barrels the right-way up and take off the lid and wire brace
  • Wait for the flames to indicate how well is the burn, then dowse with up to 3 buckets of water (careful of the steam)
  • Twist the barrel from left to right moving the water around until you know it cannot ignite again
  • Take out any large, partly-charred material which can be used for the next burn and will improve its efficiency
  • Replace the lid on the reduced material (up to one third of the height of the barrel) and stamp on it to compact it
  • Come back the following day (checking once to make sure it hasn't re-ignited) and remove the material to a pile
  • The finer stuff can be buried in the ground under new plantings as it conduces to trap minerals passing through the soil
  • The first burn will not be totally efficient


    The last thing to say is to allocate various uses to charcoal. Obviously the quality dictates the limitations. Hence, as I build up a large pile on the land I cherry-pick the larger pieces for outdoor cooking on pans, allowing for the technique to cook without flame and thus without burning the pans. The rest is buried in pulverised form beneath new plantings in order to trap washed-in minerals. I also use it in layers with sand in buried water feeders, adding liquid fertliser, which get water straight to the base of the roots without wastage. Charcoal tablets have also been used for millenia as a gut purifier. As you can imagine, it is not to everyone's taste, but as a means to purify water in the future, that is a real possibility.

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