3-Stone Stoves

When we go camping in the old days, we brought rice, set up the most primitive 3-stone stove and cook rice for food.  Now most people bring their own small but efficient stoves that use natural gas. It is quite shocking to see that most of the hundreds of families in Gikomero Sector in Gazabo District in Kigali City in Rwanda that we have visited are still cooking with primitive 3-stone stoves.

These cannot concentrate the heat in a confined space, cannot reach a very high temperature uniformly, lose a lot of heat, waste a lot of precious energy, take a long time to cook, and generate a lot of polluting and harmful smoke.  

We asked our professors in Building Services Engineering to help the villages design better stoves that are inexpensive, use local materials, and are easy to build.  After much experimentation, they decided on a 10-20 brick model, set using dried mud.  All material can be found locally, and are relatively inexpensive or free.  The key challenge is to design an enclosed space for burning with sufficient ventilation.  

When a housewife tried the new stove for the first time, she lit the fire and then went away to do other house chores, as usual.  When she returned to check on the pot, after the usual allotted amount of time, she was surprised to find that the food was already cooked and was in fact, beginning to burn.   She figured she used only half of the usual amount of wood, and yet the food cooked much faster than before.  Overall, the new stoves are twice as efficient as the old 3-stone models.  The villagers seem happy enough. 

The next challenge is the fuel.  Cooking (and construction of houses) use so much wood that essentially all the trees in the area have been chopped down.  It is increasingly difficult to find wood to burn.  The lost of trees also lead to the lost of top soil, …   Now, if only we can find a way to burn dried banana leaves, corn stalks, sorghum stalks, and other farm by-products efficiently, …