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close this book Boiling Point No. 28- August 1992
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View the document Biomass Combustion & the Environment
View the document Charcoal & the Environment - Pros & Cons
View the document Smoke Measurement
View the document Stove Emission Monitoring
View the document Successful Mud Brick Chimneys
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View the document Triple Cone Stove Burning Ricehulls & Woodsmoke
View the document "Energy Assistance Revisited - A Discussion Paper"
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Triple Cone Stove Burning Ricehulls & Woodsmoke

by Herman Johannes of the Solar Energy Research Centre, Gadjah Mada University, Yogyakarta, Indonesia. 1986

The triple cone ricehull stove reported here is claimed to be an improvement on previous designs. It is composed of three clay components: the outer cone A, the central cone B and the upper cone C. The stove may be operated as a pure ricehull stove or as a hybrid stove burning ricehulls and woodsmoke while producing charcoal.

Fig 1 - A Stove Used to Burn Ricehulls Only


Ricehulls are poured through the 3cm slit between cone A. and cone B. When woodshavings or other combustible material are dropped on this surface and ignited then this layer of hulls will catch fire and burn. Cone B. becoming incandescent will scorch the hulls in contact with it. Smoke from the burning hulls together with outside air will be sucked into B and bum off. The cooking pot may be placed on B's mouth without using cone C, but a better thing to do is to seat cone C in the mouth of A and place the cooking pot on C's mouth. In this case smoke generated outside cone B and eventually not sucked into it will be compelled by cone C to flow to the top of B and bum off.

2. The stove used as a hybrid stove burning ricehulls and woodsmoke while producing charcoal (Fig 2)

Fig 2 - A Hybrid Stove Burning Ricehulls & Woodsmoke while Producing Charcoal

The stove described may easily be converted into a hybrid stove using not only ricehulls but also woodsmoke while producing charcoal. The wood smoke is produced in a woodsmoke reactor placed on the three consoles within cone B. This reactor is nothing more than a spent milk tin of l0cm diameter and 15cm height, filled with pieces of hard wood. Eight holes of I mm diameter are nailed at the periphery of the tin's bottom at/owing woodsmoke to spurt in jets through them onto the incandescent layer of ricehull char on A's floor. This smoke then bums directly to CO2 and H2O or after being converted first to producer gas CO + H2. The reactor put in a wire cage can be lowered into or pulled out of B by a wire with a hook at its end. The reactor being put in the burning ricehull stove will be heated up and the wood within will be pyrolysed to charcoal and smoke. The glowing charcoal in the tin cannot bum to CO2 and ash because the air in it has been expelled by the smoke generated while air is prevented from entering by the jet of smoke.

Even if the outflow of smoke has ceased because the pyrolytic reactor has ended, the charcoal produced cannot bum to ash because the little air that may enter the tin will produce some CO2 that will not support combustion.

Smoke is regarded as a health hazard and hence it is discarded through chimneys in many stoves and in fireplaces burning wood for space heating in temperate zones. Discarding smoke into the air is not the best way of getting rid of it because of environmental pollution and wasting of energy. Smoke consists of combustible hydrocarbons such as tar containing methanol, acetone acid plus CO, H2, CH4 and carbon particles. Smoke contains about 55% of the heat of combustion of wood. A better way of getting rid of smoke is to use it as a fuel as is done in the hybrid stove described.

A larger triple cone ricehull stove made of clay or of steel plate with a clay inner cone or pipe may be used for drying tobacco or other agricultural products.


1. Beagle, E.C. (1978): Rice Husk Conversion to Energy, FAO, Rome

2. Harahap, Filino (1981): Utilization of Ricehulls as an Energy Source, Development Technology Centre, ITB, Bandung, India

3. Anonymous (1983). The Meechai Economical Stove, Reric News, March /983.

4. Johannes, Hermen: Simple Ricehull Stoves for Rural Households, FAO, IPB, BIOTROP Seminar Household Energy Conservation, Bogor, Indonesia, 1984



Co-ordination & Advisory Centre for Integrated Household Energy Supply (IHV), P O Box 5180, 6236 Eschborn, Germany, Tel: 6196 793004-7, Fax: 797325 Editor: E Metzen

News from Headquarters

IHV Changes Department

by IHV Editor

In April 1992, asa result of the "Portfolioanalyse", the IHV project moved from GATE to a newly established working unit of GTZ: "Farming and Household Systems" (Org. 423-4). The unit, coordinated by Dr Engelhardt, serves GTZ-supported projects that are focusing on farming and household systems. The objectives and activities of the unit are outlined here in a brief summary. Readers are welcome to apply for more information material.

The main objective is to mobilize the potentials of farming and household systems with the aim of using existing resources most effectively, as well as increasing farm and household income. Sustainability of farming systems is viewed as a pre-condition for a long term ecologically sound use of natural resources. It also secures and increases productivity of food/cash crop production and processing. Surveys have shown that 1 ha land under sustainable agricultural management can prevent the destruction of up to 10 ha tropical forest.

Approaching the main objective in an holistic way necessitates the integration of topics related to farming and household systems. These are: Project Economy; Household Energy (including small-scale enterprises); Utilization of Biogas (including ecological sound use of waste water and residues deriving from agricultural production); Eco Farming; Environment Economy in the agricultural sector. The services offered by the working unit cover these fields.

Experience has verified that development activities implemented in the agricultural sector are successful if they identify and utilize the wider potentials of farming and household systems. Prior to this, decision-making processes taking place at farm and household level must be fully understood. The obvious factors like allocation of resources (land, humanpower, capital, management capacity) have to be set into a broader context. Basic conditions under which effective resource allocation can take place are sustainability of production, the ability to balance seasonal variations in humanpower demand and supply, risk and general food supply. However, when adopting an holistic approach, more factors have to be taken into account. They range from infrastructure, cultural behaviour, macro-economic conditions, agricultural policy, supporting institutions to natural environmental conditions.

So far development work has given little attention to farming and household systems. However, the necessity for applying integrated approaches (ie. viewing factors in the context of an overall system), aiming at sustainable and ecologically sound agricultural management are becoming more and more recognized. Establishing the unit Farming and Household Systems in GTZ corresponds to this trend in development policy.


Reports on Projects

Cost-benefit Analysis of Household Energy Projects

by IHV Editor

A cost-benefit analysis of household energy projects conducted by Ms Helga Habermehl (Economist) on behalf of IHV, has shown a positive impact on household and macro-economy levels. We hope that the experience and systematic approach as outlined below will help to ease future economic evaluations of household energy projects. Copies of the study are available from the IHV documentary service.

The study compares GTZ supported household energy projects in Burkina Faso, Mali and Niger. Its two main objectives were:

1. An analysis of the economic impact of improved stoves for user households, the local small-industry and the national and regional economy.

2. The development of reliable and standardized criteria and calculation methods for such a cost-benefit analysis.

A three-stone fire, traditionally used in these Sahel countries, consumes 0.60 to 0.76 kg fuelwood per day and per capita respectively in capital cities or 0.70 to 0.80 kg in secondary towns. The average price per kg is 20F CFA in Niamey and Bamako and 24F CFA in Ouagadougou. In small towns of Burkina Faso it is set at I SF CFA, in Niger at 11 to 15F CFA. Time spent for collecting fuelwood amounts on average to 7 to 11.5 hrs a week.

The average user household in these countries was using two improved stoves. The price per stove ranged between 650 to 900 F CFA. The avenge life span of a stove was 3 years. A clay stove in urban areas of Burkina Faso lasted 2 years and in rural areas 1.5 years. When two stoves were in use, 40% fuelwood could be saved in Burkina Faso and Mali, 30% in Niger.

Criteria for Economic Benefits on Household Level

When calculating/he pay-back period of improved stoves, several variables had to be taken into account: for rural households collecting fuel (ea. in Mali and Niger), time savings for fuel collection were calculated based on the "Salaire minimum agricole garanti" as shadow income. This had been compared to expenditures for purchasing two improved metal stoves. The calculation resulted in a pay-back period of 33 days for Mali and 88 days for Niger. In the case of owner-built mud stoves in urban areas of Burkina Faso the time spent on learning the skill and actually building a mud stove was monetarized, based on the potential income that could have been achieved through adequate jobs in the informal sector. When households used two improved owner-built mud stoves the pay-back period amounted to 27 days, (for comparison: Niamey 45 days; Ouagodougou 29 days).

Another economic parameter is the net profit margin derived from the regular and correct use of an improved cooking device. This takes into account the total amount of money savings resulting from a reduced fuel consumption together with the life span of an improved stove and the expenditure for purchasing/building it. The net profit margin was much higher for households using an improved stove (Niamey: 12 to 18 times; Bamako: 14 to 70 times; large cities of Burkina Faso: 13 to 30 times). Based on the official minimum wage, it was calculated that the monthly expenditure for fuelwood amounts to 29% in Ouagadougou, 41% in Bamako and 10% in Niamey. However, the actual salaries paid in the informal sector often reach only 25-50% of the official minimum wage. The high net profit combined with the large share of expenditure for fuelwood on the monthly income result is a very positive economic impact for user households. Urban households in Burkina Faso for example, could increase their net profit by 2 to 3 monthly minimum wages per annum.

A comparison of total annual costs for different types of fuel (wood; LPG; kerosene) shows that the highest economic potential lies in improved woodstoves. For households in Ouagadougou and Niamey, cooking with an improved kerosene device had been twice as expensive; with an LPG device three times more expensive than cooking with wood. In Bamako cooking with LPG had been three times more expensive and using kerosene, even four times so. Consequently, hardly any household is using either LPG or kerosene for cooking. Commercially used dolo-beer stoves in Ouagadougou could save 30% of fuelwood per annum, increasing the annual net profit by 40%. With such saving potential a switch to other fuels seems equally unattractive.

Economic Impact for a Region

The use of improved stoves reduced the total fuelwood consumption of Ouagadougou by 8.1% in 1987, 2% in Niamey and 6.49% in Bamako. To illustrate these figures, the supply of woodland and the annual output of a natural forest under sustainable forest resource management was calculated as well as the space of land necessary to produce the additional amount of wood which would have been used if it had not been saved by using improved stoves. Taking into account the average volume of 17sq.m/ ha and a weight of 810 kg/sq.m the following area of woodlands had been needed:

Supply of Woodland equivalent to annual fuelwood savings


368 ha


1,343 ha


15,867 ha

Assuming that natural forest is 100% accessible in areas with a downfall of 800 mm the following forested areas had to be under a sustainable forest resource management:

Annual Increment of natural forest equivalent to fuelwood savings







Burkina Faso:


The annual net profit of all improved stoves per dissemination area had been calculated deriving from annual fuelwood savings, valued by its market or shadow prices and deducting the expenditure for stoves. (Shadow prices took into account the costs for afforestation, estimated costs of a sustainable resource management and the prices of substitute energy like LPG and kerosene). Based on the market price of fuelwood the net profit exceeded the initial expenditure for improved stoves considerably (Niamey: 14 times; Ouagadougou: 18 times; Bamako: 27 times). However, taking into account the highest possible shadow prices for fuelwood (here only the cost for afforestation) the net profit was 35 times higher in Niamey, 58 times higher in Ougadougou and 120 times higher in Bamako.


Results of a Study on Strategy for Household Energy in Mali

by IHV Editor

This article presents the essentials of a summary written on a study on household energy in Mali. The study was conducted in the context of Programme Conjoint d'Assistance " la Gestion du Secteur de l'Energie PINUD/World Bank ESMAP, financed by the Dutch government.

The importance of the household energy sector in Mali becomes obvious considering that 91% of the total energy is consumed in households, of which 96% is fuelwood. The utilization of modem energies has been rather insignificant so far in both the rural and urban areas. The proposed activities of the programme, either coordinated by governmental bodies or non-governmental groups, aim at a set of objectives:

• Household energy consumption should be reduced.

• Areas facing natural resource degradation should be safeguarded without deleting an important source of cash income for rural energy producers.

• Prices for fuelwood should be adjusted to their market value to avoid a negative impact for the urban poor or a decrease in tax income for the government.

• Electricity should become accessible and cheaper ensuring an acceptable economic balance for Energie du Mali (EDM).

In order to reach these objectives the study proposes the following strategies:

• More effective administration of the household energy sector offering a better energy service to the urban population. A mid and long term coordination of a political framework is therefore necessary.

• A better management of existing fuelwood producing forestry plantations since a massive substitution of biomass fuels can not be expected in the mid term. This includes establishing reliable connections between forestry and energy related activities.

• Support of local and private initiatives to relieve the burden from the government (ea. commercialization of fuelwood, land management etc.).

• Control of fuelwood that is transported and marketed in urban areas.

The programme aims at improving access Lo especially modern energies, for the urban population, contributing to a better quality of life. A sufficient energy supply contributes to economic development on a national level avoiding a negative impact on the environment. Three components of the programme are concerned with energy demand and energy devices. Improved devices like gas and kerosene cookers, improved wood and charcoal stoves and portable lamps etc. will be further developed and disseminated. Awareness and advertisement campaigns support the marketing of these products. Loans for small and mid-scale producers, "operateurs", will be made available.

The other five components define activities related to biomass supply. Guidelines to procure biomass for the cities will be developed. This includes support for professional wood producers by creating rural market networks and forms of direct support for entrepreneurs. The charcoal sector will be modernized by rationalizing production, transport and sale. Dead wood will be utilized for the supply of cities in Northern Mali. Protected state forest in Southern Mali will be put under resource management. A last component of the programme is in charge of coordinating the different activities, monitoring and evaluation and preparing the ground for changes in energy taxation. The proposed cost of the programme for a period of 5 years amounts to 9,7 million US$.

Expected large-scale results by the year 2000:

a) 22,000 t of gaz propane liquid as compared to 6,000 t according to the present trend calculation

b) 12,000 t of kerosene for kitchens as compared to an insignificant amount according to the present trend calculation

c) reduction of charcoal consumption in Bamako by approximately 40% of the present trend calculation

d) 900,000 improved metal wood stoves (675,000 in Bamako); 120,000 improved charcoal stoves; 80,000 kerosene and 225,000 gas cookers disseminated

e) an additional number of 40,000 households having access to domestic electrification of which 20,000 are in Bamako.

The results for the rural area show an afforestation of 1.5 million hectares administrated under the responsibility of local groups; afforestation of 300,000 ha (of which 75,000 ha are protected state forest) under progressive utilization; 100 rural entrepreneur groups that have established around rural markets for biomass fuel; 90% of the urban entry places for biomass fuel are under control.

According to the study the cost benefit analysis shows positive results on both the large and small-scale.500,000t of wood can be saved per annum, tax income increase and price increase of 10-20% for biomass fuel can be balanced through possible savings when using improved devices.