How it works: The angled sides of the cone control the combustion process by only allowing oxygen to the top layer where the flame is.

The area below the flame is oxygen starved but remains hot due to the flame above heating it like an oven.

This hot area is the pyrolysis zone where the biochar is made.

The heat causes flammable gasses to evolve from the biomass, which rise to the top where they are burned in the flame zone.

When no more gasses evolve (i.e. no more visible flame), the process is complete, and it is doused with water.