Illustration: Permaplans
Kon-Tiki kiln and fire pit
A cone-shaped fire that burns from the top: the flames shield the embers below from oxygen – that is how biochar is made.
The Kon-Tiki is an open metal cone or a cone-shaped pit in the ground. You light a thin layer of wood and add more whenever the top layer has turned white. The wall of flames on top uses up the oxygen – the embers below char instead of burning to ash. At the end the fire is quenched with water.
Advantages: little smoke, no technology, done in a few hours.
Safety: keep enough distance from trees and buildings, never in drought or wind, have water ready.
In Garden Survival the fire pit needs 3 m distance from every tree crown. There firewood becomes biochar: 1 rm of wood → 0.25 rm of char.