Making charcoal - open fire
I was surprised that there were no how to's for charcoal productions without the need for kilns, drums etc, so thought this might be of interest to some as a trial technique. It is not very efficient by way of volume of charcoal to volume of biomass to start, but can be useful if you have quantities of garden waste such as prunings, bark, leaves etc. This type of stuff normally goes into green waste, or needs chipping to compost or use as mulch as it is too big for compost bin.
This is a process I have used which requires only an open fire or fire pit, shovel or rake and water (hose or steel buckets with water). It is a minor modification of the techniques used when cooking using the camp oven - which only uses coals instead of flame. Instead of transferring the coals to the oven pit, they are wetted down to stop burning, and create charcoal.
Basic technique is the same as if you want to make a fire for a barbeque, or camp fire. To avoid smoke use only dry fuel. In this example we had large quantities of prunings, small branches, dry leaves, bark etc. which needed to be removed before fire season. Most fuel was 5-20mm diameter. Got good results with quantities of bark and dried leaves in another burn.
Start with a small fire, and constantly add fuel - trying to keep the fire relatively small without too much flame.
Once the initial fuel burns, either add more fuel or let it die down to a small pile with coals, often covered with a layer of ash. Once the fire stops producing smoke, or flame, it is pretty much ready. See photo below.
This is fairly advanced into the fire, showing more fuel added to fire. Below is pretty much at the end of burning all available fuel.
Once all the fuel has burnt, it is now a bit cooler and easier to remove the coals to damp them down, or just wet the entire fire down with hose - thoroughly soak the fire, raking to ensure you have wet it all down. The photo below left is the fire cone opened up to remove coals. In this case I did not have a hose nearby, but steel drums full of water I shovelled coals into. The drums are handy for this as they can then be used to carry the charcoal to the garden area - and charcoal can be crushed in the tin.
This shows a shovel full of charcoal after wetting down. I then drain the bucket or transfer from wetted fire pit to bucket, and can be crushed and used straight away. Using garden prunings rather than large branches results in smaller charcoal to start with, and easier to crush. In this case, I got around 200 litres volume of charcoal.
As yet I have not planted anything into the vegie garden beds with the charcoal added, but will now be retaining all green waste to make biochar.