2-Can Biochar Stoves

These simple stoves use natural draft rather than forced air and are continuous feed rather than batch fed stoves.

I have taken inspiration from the principles of the Japanese style ‘top fed open draft’ kilns in which a fire is set and continuous flames are maintained through ‘baby feeding’ the fire. Air does not get down past the flame to fully combust the charcoal which forms and builds up below the flame layer; the flames consume the oxygen before it can pass down.

It is not difficult to adapt them to being brought indoors as they work better when attached to a griddle or oven which is attached to a flue outlet pipe. (The flue outlet increases the draft or draw and improves combustion).

These stoves are simpler to build than tlud, anila and anila X Rocket stoves, requiring less cutting.

Variations of this stove can be made from clay.

As continuous feed stoves, they have an advantage over batch fed stoves as there is flexibility in the burn time. Batch fed stoves such as the tlud burn for a specific amount of time and heat may be required for a longer or shorter duration.

They consist of two cylindrical containers, the outer diameter of can 1 being the same as the inner diameter of can 2.

Can 1 has 2 lines of holes or 2 slots cut sloping up as shown in photo 1.


Can 2 is cut to the shape shown in photo 2.



The idea is that, by rotating can 2 in an anti clockwise direction, the holes in can 1 are shut off from the bottom, moving up1 as can 2 is turned.




until all the air inletĀ  holes can be closed



This mini prototype food tin can version does work but is not without its problems. These pictures serve to demonstrate the principle but larger stoves with more air inlet holes, handles and ideally attached to heaters and a flue outlet pipe to increase the air flow are of more practal use.



The picture below shows a variation whereby the airflow is cut off by raising the outer can up the inner can. This allows for more air inlet holes.



The above stove also features a sliding, removable floor for emptying the biochar into the removable outer can which doubles up as a biochar removal bucket.

To use the stove;

1. Turn can 2 so that the holes in can 1 are fully open and set a fire in the bottom of can 1.

2. Continue to feed sticks of dry wood onto the fire and watch as these sticks turn to charcoal.

3. As they char, turn can 2 a few degrees to begin shutting down the air entering the bottom of can 1.

4. Ensure that a continuous flame is maintained at the top of the fire in can 1 in order to ensure that air is sucked up by the flame and does not go down to burn the charcoal to ash.

5. When you no longer need heat, empty the biochar and quench it, ensuring that it will not re-ignite.