| Boiling Point No. 05 - September 1983 |
Dian Desa, Yogyakarta, Indonesia
In some parts of Indonesia a unique type of cooking stove is made of a mixture of mud and rice husks and has the following advantages.
1. It can be made from locally available resources in rice-growing areas.
2. A knife is the only tool needed for construction.
3. The stoves can be built in the kitchen or at a workshop and then transported.
4. The stoves last up to five years before they disintegrate, and can be moved around the kitchen even after a few year's use.
5. me material is strong enough so that it could be adapted to a wide variety of stove designs.
The typical stove seen is a boxlike structure with two potholes with the door in line with the potholes. The second pot is raised so that smoke can escape at the back of the stove. There are no tunnels, baffles or dampers.
The basic method of construction is the same for building one stove or many stoves, the differences are in the type of moulds used and the drying process. Larger stoves than the one illustrated can be made with the same method.
First a sandy clay that does not shrink much when it dries is mixed with rice husk (2:1 by volume). The clay is usually dug up from the rice paddies and the rice husks are collected from homes or small rice mills. A lot of water is added so the mix has the consistency of very wet mud mortar. One stove will require about 30 kg of wet mix. The mix is left to rot for about one week, by which time it has quite a strong odors. During this 'maturing' the clay particles have been broken down into smaller clay particles and more bonds have been created so the mix is stronger and more plastic. Without this the stove would crumble within a month.
The next step is to place the internal firebox mould, made of pre-cut wood pieces, banana stems, or some other filler, where the stove is to be built. Mud is packed around the sides and the rear.
After one day's drying, the mud for the top is laid on top of the form. Small bamboo pieces to support the arch sections are used in the owner-built method to prevent sagging, because the banana stems are not as stiff as the wooden mould. The potholes are roughly shaped at this time. The walls and top are about 7 cm thick. As the stove dries small cracks appear. These are removed by gently beating the stove with a coconut frond or a bunch of small branches so that the clay spreads out and closes the cracks. After one or two more days the form work is removed and the stove continues to dry. In the kitchens it dries in place, but in larger scale operations they are often made outside and the stoves are dried like bricks. They are dried flat, on one end and then on the other to promote even drying.
These stoves are strong enough and light enough (15 to 20 kg) to be carried by hand or even strapped to bicycles. In Indonesian villages these stoves can be bought for the equivalent of a day's pay for a rural worker, which means about
hours of semi-skilled labour was needed. These stoves are strong and often support pots weighing 10kg. Within a year a crack develops directly down the middle of the stove but it does not greatly impair the performance or strength.
The design could be improved by adding a baffle underneath the second pot-hole and reducing the size of the door and connecting tunnel. This would make it similar to the pottery Tungku Sae stove, which has saved about 40% compared to mud: rice husk stoves in a pilot village in central Java. However, the mud: rice husk stoves do save fuel and are more convenient than some other stoves as the following example shows.
An example of the Diffusion of the Mud : Rice Husk Stove in Indonesia
Indonesia consists of over 10,000 islands and migration from densely populated islands to lesser populated islands is common practice. In one area of south Sumatra a family from central Java brought their stove building skills with them and set up a small family industry to supply the mud: rice husk stoves to other migrants. They produce about 150 stoves every month throughout the dry season which amounts to nearly one thousand stoves per year. Without any outside assistance this family has been able to sell thousands of these stoves which are an improvement over the traditional stove since people are buying them. A traditional technology transferred via skilled craftsmen is proving to be a more efficient method of diffusion than most centrally controlled attempts at improved stove dissemination.