FAO - Charcoal, Brick kilns
Properly constructed and operated brick kilns are without doubt one of the most effective methods of charcoal production. They have proved themselves over decades of use to be low in capital cost, moderate in labour requirements and capable of giving surprisingly good yields of quality charcoal suitable for all industrial and domestic uses.
There are many designs of brick kilns in use throughout the world and most are capable of giving good results.
The brick kiln must comply with a number of important requirements to be successful. It must be simple to construct, relatively unaffected by thermal stresses in heating up and cooling and strong enough to withstand the mechanical stresses of loading and unloading. It must be unaffected by rain and weather over six to ten years.
The kiln must allow control of the entry of air at all times and during the cooling phase must be able to be readily sealed hermetically to prevent entry of air. It must be of reasonably light weight construction to allow cooling to take place fairly easily and yet provide good thermal insulation for the wood undergoing carbonization, otherwise production of cold spots due to wind impact on the kiln walls prevent proper burning of the charcoal and can lead to excessive production of partially carbonised wood pieces ("brands") and low yields. The ability of the brick kiln to conserve the heat of carbonisation is an important factor in its high conversion efficiency of wood to charcoal.