|Boiling Point No. 04 - March 1983 (ITDG, 1983, 20 p.)|
(Brian MacGarry works from Silveira House at Harare, Zimbabwe, for a church-based private voluntary organisation which carries out hardware development and runs training courses in the energy field.)
Several technologies are being used to combat the growing shortage of fuelwood in Zimbabwe: improved woodburning stoves, biogas and solar cooking. This short summary is written from the viewpoint of one of the centres involved in this work, and thus does not claim to cover all that is going on.
Two of the wood-burning stoves that have aroused interest in the eastern part of the country are the Lorena stove, and a modification of the iron frame 'stove' described by Jaz Gill in Boiling Point No 2. Both are reported by users to give 65-70% fuel saving as compared to the unmodified iron frame, and both make much more effective use of low-grade seasonally available fuels such as dry maize cobs.
Lorena stoves are generally built against the wall of the round thatched kitchen, so that the chimney can be taken out through the wall. They generally have places for three pots - one for the sadza (stiff maize porridge), one for vegetable or meat relish, and one for hot water - and often an oven.
This type of stove is favoured not only because it saves fuel, but because it produces very little smoke and it presents a more 'modern' image: young housewives want to stand to cook, while older women prefer to sit on a chair or on the floor, and the stove can be built at whatever height suits the user. This flexibility in the design is seen as a great point in its favour. Suitable material for building the stove is easily available, and techniques for using it, eg in brickmaking, are well known. Construction however is slow and some stoves have now been built partly out of brick. This is likely to become more popular.
The bulk of this stove and its consequent nigh heat capacity make for good space heating, although when families gather around the central hearth in cold weather, many prefer to see a fire in the hearth.
The Iron Frame stove is closed in with sheet metal (which can be obtained from old 5 or 20 litre tins) on three sides and the top, so as to give a sheet metal stove with an opening through which fuel is inserted and holes in which the pots sit.
This is favoured because it saves fuel, produces much less smoke, and can do all that an open fire does, no other fire is ever used to heat the house, and unlike the Lorena stove, it can be used, for example, to smoke meat to preserve it.
Both of these stoves can be built for less than Zimbabwe $5 (£4).
The advantages of both these stoves are most obvious in the area in which the iron frame grate is already widely used, and cooking is almost always done indoors, outdoor cooking being only for brewing beer or cooking large amounts of meat for social gatherings. Where more cooking is done out of doors, especially in western parts of the country, less bulky clay-and-brick stoves are gaining popularity.
The solar cooker is the next most expensive option for cooking, and the model developed is a simple absorbing box solar cooker. Such a cooker is capable of cooking a total of 3 litres of sadza and/or stew, twice on a sunny day (about 240 in an average year), and is easy to construct for a cost of about ZS40 (£32). Foam rubber sheet insulation is not the cheapest, but it seems to be the best to use as it greatly simplifies construction.
With this cooker, a new method of cooking sadza must be learned, and this deters some potential users, but a few dozen of these cookers have come into use in the past year or so. The ability of this cooker to cook common, simple dishes with little attention, its portability, (so that women can cook while working in the fields), and the fact that the pots do not become dirtied by soot, are all appreciated.
Demand is now growing for a solar oven capable of roasting meat and baking bread (at up to 200ºC). Such an oven, fitted with concentrating reflectors, and using glass wool insulation, has been tested and demonstrated. It can be produced at a cost not much greater than that of the simple cooker. Since the solar oven must be moved frequently to track the sun, it requires more attention in use, and we have yet to see whether this presents any problems.
Biogas is the remaining option; it is more costly, but a slightly modified 8 cu m version of the 'Chinese type' of digester, big enough to provide for all of a family's cooking, can be built for less than Z$400 (about £300), including the cost of the cooker. This is not prohibitive in Zimbabwe, as in the last 2 years thousands of peasants have earned more than Z$1000 annually from the sale of crops, most of which goes to capital development on the farm. Peasant families have also shown their ability to manage this type of digester.
The main modifications we have made in this digester are the use of old inner tubes as gasholders, (to minimize pressure in the digester), keeping 50 cm depth of water on top of the lid (see drawing), and painting the interior with bitumen.
Users like biogas because it saves wood, is clean, looks modern, and the digester provides improved fertilizer in the form of spent slurry. In the next stage of development, more digesters are to be built at community centres than in private homes, and this may prove the most economical system if they are to get the same attention and maintenance as those already installed.
We cannot yet conclude which of the cooking stove technologies will be most significant in the long run, maybe some new variant on one of these may overtake them all, but all seem to have a secure place in the overall picture for cooking in Zimbabwe.