| Boiling Point No. 08 - December 1985 |
|REVIEWS AND SUMMARIES|
By R. Louvel, Association Bois de Feu 1985.
This is a half way stage report (16 pages in French - for the Niger Ministry of Mining and Industry) of the project for the design, production and promotion of domestic cooking stoves to burn groundnut shell briquettes.
The report sets out the justification, aims and programme of the project and its implementation up to the stage of trials with 70 families and the first set of results. The stove was designed and lab tested in cooperation with ITDG showing a PHU (Percentage Heat Utilization) of about 30%. Louvel then field tested and optimized the design in Basso, Niger. It is a relatively simple, sheet steel stove ("Brini" see Figs. 1 and 2) with a grate, a conical combustion chamber, a fuel passage and a cylindrical outer wall, designed to give a close fitting shield to a particular size of pot.
The 'Brini' is a modification of the 'Mad Sauki' woodstove (See BP No. 7). The addition of a combustion chamber helps keep the briquettes in closer contact and improves combustion. Minor field modifications reduced smoke and facilitated lighting with only a very small reduction in PHU. Louvel reports that the standard boiling water test procedure for wood stoves needs to be modified for briquettes to take account of the difference between the value of wood charcoal and of briquette "charcoal".
Some experiments were made with a similar stove but with a mud combustion chamber. This showed almost no improvement in PHU but was much more stable and was considered to be sufficiently attractive to justify development.
The Brini stoves were made in 3 sizes to match the most popular pot sizes. A group of blacksmiths were given 2 weeks training to make the stoves and were later found to be making good stoves but were too slow to be economic (hammer and chisel method with templates) Louvel estimates that the 'Brini' No. 3 size could be made for about 900 Fr CFA (£1.50), compared with 700-750 Fr for the standard 'Mad Sauki'.
The project is now considering the merits of continuing to develop the briquette stove as compared with encouraging the use of burning briquettes and wood bagasse in existing stoves. The latter would be an interim solution whilst wood is still available and would meet the situation where either fuel might be temporarily unavailable.
The present, actual briquette production is very small in Niger, 3-400 tonnes per year, mainly because of high prices and lack of a local distribution system (22 Fr/kg compared with 10 Fr/kg for wood in Dasso). The current production capacity of Sonara (groundnut de-shelling plant in Dasso) is also small at 2800tonnes per year. Smaller semi-mechanised or manual presses may need to be explored to match local production and use. The main problems of use were feeding too much fuel at once and not cleaning out the ash after each use.
Although the initial survey results were favourable, Louvel considers the small numbers surveyed and the simple procedure do not justify firm conclusions.
The report concludes with a series of questions which need to be answered in the final evaluation. This should provide useful indications for the several countries also investigating the use of agricultural residue briquettes for domestic cooking.