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close this bookBoiling Point No. 33 - May 1994 Number 33 (ITDG - ITDG, 1994, 36 p.)
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R&D News

The better bonfire by Moses Agumba, Technical Research Officer; IT Kenya, P.O. Box 39493, Nairobi, Kenya.

In October 1992, IT-Kenya commissioned a one-year research exercise to assess and compare the costs and performances of the various techniques used in firing Upesi stoves. This was carried out by devising an appropriate testing method and applying it to a range of firing techniques to help design a better system.

The Upesi stove producers in western Kenya have been using the traditional 'bonfiring' method to fire their stove liners. The potters spend many exhausting hours coaxing their fires to reach required temperatures when the weather is not conducive to firing, for example when it is damp and windy, and orders already overdue depend on successful firing. Bonfires can also cause 50% of the liners to crack, and they consume vast quantities of grass as fuel.

The procedure used to test kilns requires 4 thermocouples probes to be placed amongst the liners. They are covered with a thin clay sheaths to protect them from being exposed to the flames which can cause temperature fluctuations. The probes are connected to a data logger which stores the readings at 10-minute intervals. At the end of the firing, the data logger is down-loaded into a computer so that the results can be analysed to show maximum/minimum temperatures, the rate of temperature increase and heat the distribution.

Performance of the Better Bonfire Kiln.

Loading capacity (Upesi stove equivalent)

Up to 120 units

Maximum temperature range

660-700 °C

Firing duration

9 hours

Temperature increase rate

75 °C/hour

Cooling duration

20 hours

Temperature decrease rate

32.5 °C/hour

Fuelwood consumption

20-25 kg/Upesi stove fired

Operational labour requirement per load

20 man hours

Cost of kiln

KSh 5660

Cost of shelter

KSh 7500

Life expectancy of kiln and shelter

2-3 years

The Better Bonfire is a simple kiln which is quick and easy to construct, taking only five days to build using 400 local bricks and local soil as the mortar. The firing chamber is 1.5 m diameter inside and has a retaining wall 0.72m high. It costs approximately KSh 6000, about one tenth of the price of an enclosed kiln.

The liners are loaded via the top, and they sit astride 6 walls that form combustion channels where the fuel wood is placed. The liners are stacked higher in the centre than at the outside, forming a dome. They are covered with broken pots, then grass with a thin layer of mud smeared over it. This cover lasts for one firing, and serves the purpose of keeping the heat in.

Small holes and cracks which appear in this cover during firing allow some smoke to escape, and create a small chimney effect necessary for combustion. Fires lit in the fire boxes are adjusted to maintain a steady burning rate and to give the desired maximum kiln temperature.

Tests have shown that the Better Bonfire saves as much as two thirds to a half of the fuel used in a traditional bonfire and that liner losses are reduced to below 10%. The Wise Women group, who helped to construct the prototypes, are very happy with the better bonfire, and two other women's groups, Keyo and Ichingo, have also built them with supervision from IT staff.

A simple manual detailing the method of construction and how to operate the better bonfire is being prepared for other organizations in East Africa who have expressed an interest in using it for traditional pots.

For details of this manual, please write to IT-Kisumu, P.O. Box 284, Kisumu, Kenya.

Indoor air pollution at Theri-Garwhal, India - a project proposal by Dr Helmut Stoedter, Environmental Concept/GTZ, P. O. Box 5180, Eschborn, Germany.

An Indian NGO, TATA Energy Research Institute (TERI) has for several years been disseminating 'improved chulhas' in rural areas of India. The advantage of these is their capacity for saving firewood and energy and, most importantly, diminishing the exposure of women to smoke from open fires in closed rooms. This particular problem has been investigated by TERI with respect to particulates and carbon monoxide (CO).

On behalf of GTZ, two experts from Environmental Concept, Dr H. Staedter and Dr D. Boehning, worked with TERI to investigate more fully the situation of women's exposure to indoor air pollution in Garhwal. They visited health stations, clinics and hospitals and checked the availability of the conditions needed for chemical analyses and measurements of smoke exposure and procedures for collecting statistical data.

Reports from institutions, hospitals and doctors showed a high prevalence of acute respiratory syndrome among the female population in the Garhwal region. Since this is most probably due to exposure to indoor air pollution from cooking, it was decided that the group should examine the comparable exposures and the health effects for women using traditional chulhas and improved chulhas. They also evaluated the data already collected concerning the health effects of exposure to smoke in the Garhwal region.

TERI has submitted a pre-proposal to GTZ for a project in this field along with a comprehensive overview of the situation.

There have been several studies over the years to evaluate the benefits of improved stoves in different parts of the world. These studies usually concentrate on one aspect of the problem; they are either epidemiologically oriented to the health effects of improved stoves or are chemically based and only deal with the concentration of certain chemicals in the indoor atmosphere. There have been few attempts to find a correlation between those parameters as will be the purpose of this study.