Designing an Improved Domestic Cookstove on a Charcoal Basis in Sub-Saharan Africa

In Sub-Saharan Africa, the traditional charcoal stove is fairly similar across a range of countries; it is commonly called "Malagasy stove" -- perhaps in reference to its origin. An improved cookstove is first and foremost a stove consuming less charcoal than the Malagasy stove. But its design requires that other constraints and conditions are taken into account to allow for a massive and dynamic distribution. Thus we will start by examining the specifications and requirements of improved cookstoves. We will then present some approaches that can improve domestic stoves before briefly presenting recommended methods of testing stoves.


1. Specifications for an improved domestic cookstove on a Charcoal basis in Sub-Saharan Africa

Compared to a traditional stove, an improved cookstove on the one hand has to save charcoal, but on the other, it must also address much more complex requirements in order to win the support of all the actors involved: 1) the families, who make the final decision on whether or not to buy an improved cookstove; 2) the craftsmen, who decide whether or not to produce and commercialize the improved cookstoves instead of their traditional stoves, and 3) donors and funding agents of projects aiming to spread the use of improved cookstoves, who do so in order to reduce the cutting down of forests, to reduce greenhouse gas emissions and to improve health conditions of domestic cooking for the population. In addition, the success of improved cookstoves also depends on the following conditions: 1) the necessity of a spread of improved cookstoves that is both massive and fast enough, 2) the availability of the raw materials close to the manufacturing places (reclaimed sheet metal and the right clay for pottery, and 3) the transportability of improved cookstoves into rural areas that cannot produce them for themselves and have to import their stoves from a distant city.All these constraints and conditions need to be taken into account, without losing sight of the fact that the primary reason for promoting improved cookstoves is the expected savings in charcoal.

1.1. Motivating families to choose an improved cookstove when they replace their stove

On average, a traditional cookstove has a lifespan of two years. Only the poorest families will continue using their stove if it is perforated or even broken, delaying the expenditure of replacement much longer. For the spread of improved cookstoves to be massive, it is necessary that these families decide to replace their traditional stove with an improved cookstove, which they will not do unless they are convinced:that the improved cookstove will indeed mean savings in fuel. This is by far the most important motivation for the families (more precisely the women, who are the ones generally responsible for this purchase) when it comes to changing their buying habits.that the improved cookstove reduces smoke and soot, which affect their health and stain their pots and the inside of the house.that the improved cookstove is easy to use and does not require training. This point is all the more important as frequently it is a young cousin or maid who cooks, someone who is not directly interested in an economic use of charcoal.that the possession of an improved cookstove comes with social recognition, that it is better-looking than a traditional stove in form and colour, and that it is more solid and long-lasting. These subjective considerations can matter greatly at the moment of decision of which stove to buy.The design of an improved cookstove will have to take into account each of these expectations, and the distribution program will have to attempt to popularize and prove each of these arguments. Before massive distribution, it is further important to have a prototype tested in practical use by several families and to gather their comments and suggestions before finalizing the design of the model.

1.2. Motivating craftsmen to decide to produce and sell improved cook stoves instead of traditional stoves in the long term

Craftsmen who manufacture domestic charcoal stoves depend on their weekly sales to support their families: they are thus very vulnerable. If they decide to produce improved cookstoves, it will be by replacing their production of traditional stoves, as they do not have sufficient financial resources to buy the materials for improved cookstoves in addition to their traditional line, and some will not have the production capacity to produce more stoves during the week than they already do in general. An analysis of their economic situation allows for a better understanding of their rationale towards the innovation that improved cook stoves represents for their market. The most innovative craftsmen (frequently those who are not the leading sellers on the stove markets) will agree to produce a few improved cookstoves as a replacement of traditional stoves, under the following conditions:Producing improved cookstoves enables them to earn more money without requiring more expenditure: they are very conscious of the costs related to the production of stoves (the purchase of sheet metal in particular), as they often do not have any savings.They can put in slightly more work to produce an improved cookstove, but on the condition that their weekly production of improved cookstoves is of equal absolute value than the weekly production of traditional stoves was.It is essential that the first improved cookstoves, that the first craftsmen took risks to produce, are sold! If these craftsmen return with unsold improved cookstoves, they will not have sufficient money to pay for their food and for the supplies to make new stoves in the following week. Furthermore, they would send a very negative signal to the community of craftsmen. For this reason, the project UPED in Madagascar had unsold stoves bought by “strangers” at the end of the market during the introduction and massive distribution phase of improved cook stoves. These improved cookstoves made it possible to have a stock and avoid a rupture in supply of the market when there were specific events (International Women's Day, for example).The production of improved cook stoves has to be compatible with the technical expertise of local craftsmen: these craftsmen generally do not have a workshop but work at home with their families or outside, with rustic tools. The craftsmen dealing in sheet-metal generally know the techniques of making sheets out of 220 liter bitumen or oil barrels (purchased from companies carrying out public roadworks), by using marking templates and a chisel and putting together by folding, fastening, riveting. They do not, for example, generally weld. If one respects these technical skills and the craftsmen's experience, the innovations suggested with an improved cookstove could be introduced easily by offering marking templates that correspond with the specifications of an improved cookstove. Therefore a project of massive distribution has to be conscious of and educated on the scene of local craftsmen before making a start in a particular community.The manufacture of improved cookstoves must be compatible with access to raw materials: the supply with reclaimed sheet metal is never guaranteed. As these craftsmen do not have any savings, they cannot buy batches of the barrels that companies building roads put up for sale from time to time once asphalting is complete at a particular building site. Tradesmen play the part of wholesalers, taking a more or less important share according to the market of supply and demand. Increasing the demand for sheet metal for the manufacture of improved cookstoves can have the effect of increasing the price per unit on a sheet on the market for reclaimed goods. The existence of potters in a local communtiy depends on the existence of appropriate clay for pottery. Not all villages in Sub-Saharan Africa are located in regions with suitable ground. As it is not profitable to transport clay to manufacture stoves, it is useful to produce improved cookstoves that are partly made of clay in regions with adequate resources and then to export them to other communities.Finally the production of improved cookstoves has to be compatible with the financial resources of the craftsmen. They do not have access to credit and must live and produce based on the money they earn from selling stoves on the market. The cost of production for an improved cookstove must therefore remain roughly comparable to that of a traditional stove.Respecting all these constraints is the condition for a plan to sensitize, inform and train the volunteer artists, allowing them to take the risk of being the first to produce improved cookstove instead of traditional stoves and to continue to do so in the long run.

1.3. How the distribution program can reach a significant size quickly enough to have an impact on forest depletion

A program of distribution of improved cook stoves will only have a reasonable impact on deforestation if:a significant percentage of households replace their traditional stoves by improved cookstoves. It is therefore important to plan an improved cookstove for the greatest number of families living in an area, and not merely for a small group of users (for example the wealthiest families). This means that a good compromise between the economic performance of an improved cookstove and the capacity for distribution to the greatest number (which very much depends on the cost) has to be found. In other words, it is preferable to reach 75% of a population with an improved cookstove that saves 30% of charcoal than to bring an improved cookstove saving 50% to merely 10% of the families.the market penetration of improved cookstoves is fast enough. On the one hand, the consumption of charcoal in an area grows along with population increase, which is generally important in Sub-Saharan Africa. On the other, the introduction of improved cookstoves will reduce the total consumption of charcoal proportionally to the rate of substitution of traditional stoves with improved cookstoves. The balance will thus depend on these two factors, demographic growth rate vs. the rate of substitution. If the latter happens too slowly, its effects on charcoal consumption will be invisible because of the effects of demographic growth. For the strategy of getting out of the firewood crisis, this means that the improved cookstove project will not give the forests the few years of respite that would be essential to enact structural changes for strengthening and diversifying the supply with cooking energy.The plan for improved cookstoves therefore has to lead to models that are compatible with these constraints on a massive and dynamic distribution.

2. Testing Domestic Charcoal Stoves

Two tests are generally recommended to measure fuel savings of a stove: the “water boiling test” and the “test of [comparative cooking/compared kitchen]”. Also recommended is to measure emissions of greenhouse gases and other pollutants in the smoke.

2.1. The Water Boiling Test (WBT)

The Water Boiling Test (WBT) allows, in a simple and fast way, to assess the thermal behaviour of a stove, meaning its efficiency at extracting energy from the fuel and transferring it to the pot. It does not evaluate how efficiently energy transmitted to the pot is then used (or not). The test allows to measure the relation between the energy the stove transmits to the pot and the energy contained in the burning fuel. This test also measures the power of a stove and its specific consumption.[1]

The protocol for WBT

  • Note the weather conditions: ambient temperature, wind intensity (strong, medium, weak), relative humidity (taken from a hygrometer or recorded by a nearby weather station)
  • Weigh the empty pot (with a perforated lid and a thermometer) and note the weight Pe.
  • Fill the pot to 2/3 of its capacity with water. Place the lid and thermometer.
  • Weigh the full pot, always with lid and thermometer and note the weight Po.
  • Note the temperature of the water in the pot.
  • Clean the cook stove thoroughly before weighing it empty and note this weight CSe.
  • Fill the stove to the brim with charcoal.
  • Light the fire with twigs or a tablespoon of kerosone (10 to 15 ml) WITHOUT putting on the pot.
  • Five minutes after lighting, weight the full stove and note its weight CSo.
  • Put the full pot on the fire, place the lid and the thermometer, and start measuring.
  • If there are shutters on the doors, these need to remain open.
  • Measure the temperature every five minutes without moving the pot or the stove and note.
  • When the water reaches boiling point, note the time BT.
  • Weight the complete pot - water, lid and thermometer included - and note the weight P1.
  • Weigh the full stove and leftover charcoal (without the pot) and note the weight CS1.
  • Put the pot back on the stove and close the shutters, if they exist, for 60 minutes.
  • Make sure the water temperature does not drop below the boiling point; if it does, the test is no longer valid.
  • 60 minutes after the start of boiling, weigh the entire pot and note the weight P2.
  • Weigh the stove - including the remaining charcoal and embers - and note the weight CS2.

Terms of results

BT Time necessary to reach boiling point (min.)

SBT Specific boiling time = time necessary to bring one liter of water from 0 to 97°C (in min/l)

PHUI Percentage of heat used for the first (initial) phase (phase of high power leading to boiling) = relation of energy held in the pot to the energy freed by combustion in the first phase (in percent)

SC1 Specific fuel comsumption in the first phase = amount of charcoal necessary to raise one liter of water from 0 to 97°C (g/l)

Pw1 Power during first phase = amount of energy produced during the first phase per time unit (kW)

PHUT Percentage of total heat used = relation between energy contained in the pot to the energy produced from combustion during the whole text (in percent)

SC2 Specific comsumption in the second phase = amount of charcoal necessary to raise one liter of water from 0 to 97°C (g/l)

Pw2 Power during second phase = amount of energy produced during the first phase per time unit (kW)

TC Total consumption of charcoal during the test (g)

EW Amount of evaporated water during the entire test (l)

F Flexibility = relation of the power of the first phase to the power of the second phase

Modes of calculation for the first phase :

Coefficient of correction of original water temperature: (To – T1)/To

Co 4,18 kJ/kg. C°

Li 2 260 kJ/kg

LHV Lower heating value = 29 000 kJ/kg

Mw Original mass of water (g) = M1 - Mv (M1 = weight of pot full of water and Mv = weight of empty pot)

Mch1 Original mass of charcoal (g) = Fo – F1 (Fo = weight of stove filled with charcoal [including/before?] the placement of the pot and F1 = weight of the stove and the leftover charcoal at the end of phase 1)

Mev1 Mass of evaporated water (g) = Mo – M1

R Output in % = [[(Co x Me x DT) + (Li x Mev1)] / (PCI x Mch1)] x 100%

Pw1 Power of first phase (in kW) = (PCI x M ch1) / TE (mn) x 60 x 1000

SC1 Specific consumption in first phase (g/l) = (Mch1 / Me) x {(To – T1)/To}

SBT Specific boiling time (min/l) = (TE / Me) x (To / To – T1)

Modes of calculation for the second phase :

Pw2 Power of second phase (in kW) = (PCI x M ch2) / «30 x 60 x 1000

Mch2 F1 – F2 (in g)

SC2 Specific consumption in second phase (g/l) = (Mch2 / Mev2)

Mev2 M1 – M2 (g)

Modes of calculation for the entire test of boiling :

MEV Mo – M2 (g)

R [(4,18 x Me x DT x 2260 x MEV) / (PCI x MCH) ] x 100%

TC Total consumption of charcoal (g) = Fo – F2

F Flexibility = F1 / F2

Limits of interpreting WBT

The interpretation of the results must take account of the difficulty of precisely controlling certain parameters, such as for example the quality of lighting, the homogeneity of the charcoal, as well as how well the lid of the pot seals. This is why it is advisable to carry out at least five WBT per stove.

With the results laid out above, this test makes it possible to characterise the thermic behaviour of a stove in absolute terms. However, it does not make it possible to say if it will allow for energetically economic cooking or not. A stove can, for example, have a very good efficacy percentage for heat used in total (PHUT), and still consume more charcoal to produce a dish than a stove with a lower PCUT, because the energy transferred to the pot is not always completely used for cooking : in a phase of simmering (low power), it is enough to maintain food at a temperature lower than boiling point (about 85°C for the Romazava stew, presented below): the WBT thus does not simulate the conditions of real cooking. Any excess of energy in the pot during such a phase will evaporate water, which carries the risk of dirtying the walls with food residue, densifying the sauce, hardening the meat, all without cooking the food any faster. Vaporisation (water-steam phase shift) is known to consume much energy; very unnecessarily in this case.

This is why, once the thermal characteristics of the stoves are known, their charcoal consumption during the preparation of actual dishes needs to be compared. This is where CCT comes in.

2.2. The Controlled Cooking Test (CCT)

A Controlled Cooking Test (CCT) consists of measuring charcoal consumption of a stove during the preparation of a dish. This test makes it possible to compare the performances of consumption of several stoves, under realistic conditions. The choice of the dish of reference to be prepared comes from socio-economic investigation into consumption of domestic energy before the start of an improved cook stove project. Below, we will present the protocol of CCT used in Madagascar in more than 800 tests of stoves: the dish of reference is Romazava beef stew, that is to say rice accompanied by a sauce made of leaves and meat. The recipe used is for 6 people, a size representing the average family in Antananarivo.

The CCT protocol

The preparation of the sauce and the rice is done separately and in parallel on two identical stoves.

  • Weigh pot A and its lid empty
  • Weigh pot B and its lid empty
  • Weigh the cook stoves CS1 and CS2 empty
  • Fill each stove with charcoal (allow each cook to fill the stove the way he/she is used to do it)
  • Weigh stoves CS1 and CS2 full

Preparation of the sauce in pot A on stove CS1 :

  • Weigh 500 g of beef
  • Weigh 150 g of tomatoes, washed and chopped
  • Weigh 30 g of onions, washed and chopped
  • Weigh 660 g of green leaves, washed and shopped
  • Light the stove CS1 with a tablespoon of kerosene (10-15 ml) and note the time
  • Put the beef, tomatoes and onions together with a tablespoon of oil into pot A and weigh pot A full with its lid
  • Put pot A on the stove, start cooking (start by cooking the ingredients without water) and note the time
  • Add 2000 g of water, 25 minutes after cooking has started
  • Add the green leaves to the stew, add salt to taste, and note the time
  • Add charcoal only if necessarly and after having weighed it
  • As soon as the cook estimates that the stew is finished, the test is over. Note the time.
  • Weigh pot A with content and lid
  • Weigh stove CS1 with the remaining charcoal and embers.

Preparation of rice in pot B on stove CS2:

  • Start after the cooking of the stew in pot A has begun:
  • Add 1750 g of water to pot B
  • Light the stove CS2 with a tablespoon of kerosene (10-15 ml) and note the time
  • Note the time when you start cooking
  • Weigh 1000 g of rice
  • Wash rice, add to pot and note the time.
  • When the cook estimates the rice is ready, note the time and:
  • Weigh pot B with its contents and lid
  • Weigh stove CS2 with the remaining charcoal and embers.

Terms of results for the test with the sauce

Q.I Original quantity of charcoal

T Cooking time for the stew (min), an important indicator for the cooks

CONSO Actual weight of charcoal consumed during the cooking of the stew, which indicates how economic a stove is in comparison to another

CONSO/RAW Actual weight of charcoal consumed in relation to the weight of the raw ingredients in the pot (g/kg)

CONSO/COOKED Actual weight of charcoal consumed in relation to the weight of the cooked food at the end of the cooking process (g/kg)

COOKED/RAW Relation between the weight of the cooked dish and the weight of the raw ingredients put into the pot, which will allow a comparison of the cook and their cooking process from one CCT to the next: a constant relation will indicate that the cooks have identical ways of cooking, and therefore a particular cooking style has not influenced the results of the test.

MEV Mass of evaporated water (g), allowing for a localisation of a main loss of energy, the heat used to transform water from one state to the next without benefiting the cooking of the dish

Terms of results for the test with the rice

Q.I Initial quantity of charcoal

T Cooking time of the rice (min)

CONSO Actual weight of the charcoal consumed for the cooking of the rice (g)

MEV Mass of evaporated water (g).

Limits of interpretation with CCT

The cook influences results to a degree, as she decides the initial load of charcoal in the stove, and the cooking time of the stew and rice. For this reason, when testing different of stoves, it is necessary to carry out six tests of comparative cooking at least (always with the same recipe), and to have all the stoves tested by the same cook. If there are too many CCT and it becomes necessary to resort to several cooks, then each stove should be tested by each cook as far as possible, to reduce as much as possible the influence of individual cooking styles on the results.

The calorific value of the charcoal also influences the results of the CCT. This is why it is necessary to have enough charcoal on hand for all the CCT and put it together by mixing the contents of several coal bags of different sources.

The CCT only relates to one dish, which, even if it is characteristic of the local culinary practices, does not represent all the types of dishes prepared by a family.

This being said, only the CCT allows for a comparison of consumption performance of two stoves, which is what interests the families and which is at the heart of the concerns of all promoters of improved stoves. CCT does not allow us to predict exactly what the charcoal consumption will be, but it can certainly tell which one of the stoves is the more economical one in a realistic setting.

2.3. Tests on smoke emissions

There is no "official" test for measuring how much smoke is emitted by the stoves.Two approaches have been tried:

Direct measurement of emissions at the source, that is to say on top of the stove: a filter is placed on top of the stove which measures carbon monoxide and all particles in suspension in the gases coming out of the stove.

Indirect measurement: measuring the impact of the stove on the quality of the air of the place where it is used. This is the method that is easiest to implement. Is has for instance been used by the World Health Organisation (WHO) to measure the air quality in kitchens in Ethiopia in 1994.

Both methods require equipment, means and competences that most promoters of improved stoves do not have.

3. Concept for an Improved Domestic Cookstove on a Charcoal Basis in Madagascar

The analysis of tests on domestic charcoal improved cook stoves used primarily for the preparation of boiled and simmered or fried dishes allows to draw a number general conclusions which can be applied to the design and concept of new improved cook stoves meant for the same purpose:

  • Traditional charcoal stoves are too powerful for the culinary preparation they are meant for ;
  • Traditional combustion is very energy intensive.

3.1. The traditional charcoal stoves are too powerful

A good improved cook stove needs to have adjustable power, to adapt to the energetic needs of different dishes throughout the preparation, because the energy requirements in the pot change over the course of cooking. Consider for example the preparation of rice (or pasta/ noodles) and a stew:

Preparation of rice or pasta/ noodles:

For cooking rice (or pasta/ noodles), there are two distinct phases with different energy needs:

  • A first phase consists in bringing water to the boil: this phase can be shortened if a lot of energy is transmitted to the pot. But this way of saving time happens at the price of fuel overconsumption. Moreover, using a lot of energy only allows to gain a few minutes, which is hardly noticeable if you consider the total time it takes to prepare a meal for a family of six; then
  • A second phase is the cooking of the rice itself: energy is used for maintaining the temperature of the water at boiling point. Any additional energy is used for water vaporising: this conversion of water to steam is very energy-intensive and does not influence the overall cooking time.

Preparation of the stew:

Cooking the stew requires a simmering time that is much longer than the cooking time of the rice. During the entire cooking of the stew, the energy is used for maintaining a temperature of 85°C for the ingredients. All energy that is additionally transmitted will be used for vaporising water: this conversion of water to steam is very energy-intensive and does not influence the overall cooking time-- on the contrary, in the absence of water, the ingredients are at risk of burning and staining the walls, and meat becomes hard and stringy.

This analysis suggests two prinicipal recommendations:

Recommendation n°1. Reduce the volume of the combustion chamber to a strict minimum

The larger the volume of the combustion chamber[2], the more the cooks have the tendency to put a great amount of charcoal into the stove, and thereby to spoil energy and the power of the stove. The tests on traditional charcoal stoves show that they are (much) too powerful for preparing the boiled, simmered and fried dishes. This observation is all the more important as it is the cooking of stews that consumes the most charcoal: it takes up about 70% of the total charcoal consumption for the preparation of a dish of rice and stew. In Madagascar, systematic tests have shown that the volume of the combustion chambers of traditional stoves was usually in the range of 2.800 to 3.500 cm3, although a volume of 1.400 cm3 would be sufficient for the needs of Malagasy cooking. The photographs below show the square versions of a traditional stove and an improved cook stove "Dago" (blue) on the left and on the right the round versions of a traditional stove and the "Dago" (green).

 



By reducing the volume of the combustion chamber of the improved cook stove ""Dago" to 1.400 cm3, it has been possible to reduce the power of the stove and to decrease the amount of needed charcoal by more than one third. Reducing the stove’s height and spreading the base has also allowed to make the stove more stable.

The most appropriate volume of a combustion chamber can be assessed through a "socio-economic study on the consumption of domestic energy of households" recommended in the methodology for planning a widespread distribution program for improved cook stoves.

To adjust the improved cook stoves to the size of local families, it is suggested to produce a range of different improved cook stoves: in principal, two different sized improved cook stoves should be enough to cover the needs of one family.

Recommendation n°2. Control the volume of air that circulates through the charcoal in the combustion chamber

To burn, charcoal needs oxygen and therefore air. The more charcoal and air mix, the more charcoal can burn at the same time and the more active the combustion is : the power is higher. However, this power needs to be controlled, and reduced, especially in phases of simmering. There are several possibilities for power regulation:

  • Air flows in through a door. The size of this door can be optimised so that no more cold air (that needs to be heated by charcoal) than necessary is let in. The traditional Malagasy stoves have doors of 38 to 135 cm2, the improved cook stove Dago of only 41 cm².
  • The air warms up and, through thermosiphon, tends to rise. A grid lets the air pass into the combustion chamber, where it will thread through coal to move into the free air, around the walls of the pot. This entry can be controlled in two ways: 1) at entry, with a door, which makes it possible to regulate the amount of air depending on the position of the door, or 2) or at exit, by controlling the space through which the hot air can leave the combustion chamber. The advantage of the method developed by UDEP in Madagascar is that it is cheaper to manufacture (no articulated door) and that it does not require human intervention, contrary to the door that needs to be opened, half-opened or closed according to the stage of cooking. This method works by putting three notches in the high part of the chamber of combustion, to let out only a selected volume of hot air during all stages of simmering.



This concept works as follows: at the beginning, the cook fills the stove with charcoal the same way he/she is used to do with the traditional stove, meaning up to the brim of the combustion chamber. Then he/she puts the pot on the charcoal. At the start of the cooking process, a lot of charcoal is ready to burn and the air can freely circulate and escape along the sides of the pot: the power of the stove is at its maximum. This indeed responds to the energetic need of this stage of rising the temperature for cooking the stew and boiling the water for the rice. Gradually, as the charcoal is consumed, the pile of charcoal shrinks and the pot, resting on that pile, is lowered as well. This narrows the exit paths for the hot air at the pot's sides until the pot comes to rest on the top of the combustion chamber of the stove, whose diameter was reduced (at the same time as the volume of the chamber). At this point, the pot will seal the exits for the air. The flow of air across the charcoal is automatically reduced; with less air, the combustion slows down and the power decreases, which corresponds, as we saw, with the energy needs for this stage of cooking the rice or letting simmer the stew. For pots with a smaller diameter than the stove, three embossings have been added to the walls of the combustion chamber, which will have the same effect by regulating the exit of air along the sides of the pot.

3.2. Traditional practices are not economical

The design of the stove certainly has a direct impact on the charcoal consumption for preparing a standard meal… however how the stove is used throughout the cooking process also strongly influences how much charcoal is needed in the end. Below are several recommendations of "energy saving practices" for the use of fire and cooking, easy to put into action even with traditional stoves, and which can mean saving of up to 10 to 25% of fuel!

Recommendation n°1: Do not light the stove until you are ready to put the pot on

Some families start by lighting the stove even before they have all their ingredients ready for cooking, i.e. before the vegetables are washed, the meat is cut and the rice is cleaned. As a consequence, the stove burns charcoal needlessly for several minutes. Tests of lighting carried out by UPED in Madagascar have shown that after lighting, a stove placed open air burns up to 25% of the charcoal in its combustion chamber within the first fifteen minutes. Before cooking even starts, a quarter of the charcoal is already gone, and utterly wasted!

A first recommendation is to only light the (traditional or improved) stove only once all kitchen utensils and food ingredients are ready and to put the filled pot 2 or 3 minutes later.

Recommendation n°2. Do not overload the stove

With experience and paying a little attention, the housewife should well be able to tell what quantity of charcoal is necessary for cooking any given type of meal, for a given quantity. A stove filled with too much charcoal will deliver excessive power and will consume more charcoal than one that is filled correctly. The initial filling is good when at the end of the cooking process, there are no remaining embers in the stove.

Recommendation n°3. Do not refill charcoal during cooking

Housewives often tend to add charcoal during the simmering process, thinking this will accelerate the cooking. Tests carried out by UPED in Madagascar have shown that these additions of charcoal actually lengthen the cooking process and increase the consumption of charcoal. Indeed, during the simmering phase, only little power is required to maintain a continuous temperature of 85°C in the pot. Heightening the power during this phase does not speed up the cooking; on the contrary, the extra energy in the pot is used needlessly to vaporize the water in the stew.

Recommendation n°4. Put the rice in cold water at the beginning of the cooking

Often, the rice is put into boiling water; tests have shown that this practice consumes more charcoal than putting the rice in cold water, before the start of cooking. By putting the rice in water beforehand, the time it takes to cook is reduced as well.

Recommendation n°5. Reduce the initial amount of water for cooking rice with improved cook stoves

Improved cook stoves are less powerful and evaporate less water. Especially the energy of vaporization is saved. It is therefore not needed to heat up more water in the pot than necessary. When cooking rice with an improved cook stove, energy and charcoal can be saved by putting less water in the pot.

Recommendation n°6. Extinguish the embers to recover unused charcoal and accordingly adjust the use of charcoal the next time

Recommendation °2 suggests not to overload the stove, so that no embers remain at the end of cooking. Before exactly knowing how much charcoal is needed for cooking, it is recommended to extinguish the embers at the end of cooking, to be able to reuse them the next time.

[1] The power of a stove is related to the amount of charcoal which burns per unit of time. The more powerful a stove is, the more charcoal it consumes per minute… and the more energy it delivers per minute. Generally speaking, a more powerful stove consumes more charcoal per minute than a less powerful one.
[2] The combustion chamber is the part in a stove where charcoal is placed and burned. The shape of the chamber is usually conic (for round stoves) or pyramidal (for square stoves)

by René Massé



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