J.D. Keita
J.D. Keita is Regional Forestry Officer at the FAO Regional Office for Africa, Accra, Ghana.
In the Sudano-Sahelian countries of Africa, the supplying of domestic energy demands is the major forestry problem.In this article, the author presents a step-by-step comparison of the energy balance for fuelwood and for charcoal used as a domestic fuel. He reviews the forest policy implications of his findings and tells how meeting energy needs can contribute to improved forest management and production in the region.
· Fuelwood is the major source of domestic energy throughout the Sudano-Sahelian zone of Africa. In some cases the wood is burned directly. In others it is first converted to charcoal.
As populations grow and urbanization continues to increase, urban fuelwood needs will also grow. This will have significant implications for the management of forest resources. On the one hand, it will put even heavier demands on these resources. At the same time, however, it may open up new opportunities for improving forest management by providing economic incentives that have until now been lacking.
This article explores one way in which these new opportunities might be realized, by first comparing the relative merits of charcoal versus wood from an energy point of view and then suggesting the forestry policy implications of increased charcoal use in urban areas.
Many factors influence the choice of fuels, including availability, price, tradition and personal preference, and these factors must also be taken into account in discussing the subject of fuels.
It should also be noted that, for ease of explanation, the following energy comparison necessarily deals with a relatively narrow range of variables. In reality, conditions can vary widely in regard to such elements as wood moisture, available technology, stove efficiency and so forth. Therefore, the results presented below are intended to illustrate basic principles.
From an energy viewpoint, then, which is better: wood or charcoal? Each has its proponents: the supporters of direct wood burning claim that charcoal-making wastes a lot of energy. Charcoal advocates say this overlooks the fact that charcoal has a much better energy yield than an equal weight of wood. Therefore, a real energy balance of the process involved should first be drawn up to determine if there is a global energy waste in turning wood into charcoal instead of using it directly.
Whether wood or charcoal is used, other forms of energy are also required and, in developing countries without oil resources, account must be taken of the petroleum bill in all aspects of economic life. So the two fuels also need to be compared from the standpoint of the consumption of imported fossil fuel necessary to put them on the market.
In the following calculations the heating value of wood is assumed to be generally around 3500 Kcal/kg for green wood. Dried wood can give 4500 to 4770 Kcal/kg. In the case of charcoal, the heating value varies little around 7500 Kcal/kg. To the petroleum product an average of 10000 Kcal/l is assigned.
When fuels such as wood, charcoal and petroleum are burned, only part of the total energy of the fuel is effectively utilized. This useful energy component is called the thermal energy yield, expressed as a percentage of the total energy available in a kilogram of raw material. For example, if in using an inefficient three-stone stove, only 8 percent of its potential energy is effectively used in cooking, the thermal energy yield of that particular use of the wood is 8 percent. Using a more efficient stove would increase the thermal energy yield of the same quantity of wood since it would direct more energy to cooking.
A stere (cubic metre) of wood varies considerably in weight; from 215 kg for steres of twisted branches of Sahelian shrubs up to 600 kg for steres of well-shaped wood from thinning operations. Finally, the average yield of carbonization (the charcoal-making process) varies from 16 to 30 percent of the weight of the raw material, i.e. 1 kg of wood will yield 0.16 to 0.30 kg of charcoal. The drier the wood used, the higher the yield will be.
Although carbonization causes a loss of energy, the charcoal produced gives a higher yield in use than wood. Thus, the thermal energy yield of wood is, on average, 8 percent and can even go as low as 5 percent with the popular three-stone African stove. Charcoal has a thermal energy yield of about 28 percent.
In general, charcoal wastes less energy than wood if the useful energy derived from a quantity of wood used directly is lower than the useful energy derived from that same quantity of wood converted into charcoal. In fact, 1 kg of wood gives 3500 (Kcal/kg) × 0.08 (thermal energy yield) = 280 Kcal; 1 kg of wood processed into charcoal (carbonization yield 20 percent) gives = 1 × 0.20 × 0.28 (thermal energy yield) × 75.00 (Kcal/kg) = 420 Kcal. Thus there is a net wastage of 140 Kcal of energy if, instead of processing the wood into charcoal (even with a low carbonized yield of 20 percent), it is used directly in a stove yielding 8 percent or less. Of course, this is only one example.
A series of simulations can be made by varying the calorific value of the wood, thermal yield of utilization and carbonization yield (see Table 1). According to the assumption on which the data of Table 1 are based that wood is as advantageous in terms of energy when burned directly instead of being processed into charcoal, it would need to attain thermal energy yields of 12, 9.3, and 8.8 percent, respectively, for calorific values of wood of 3500, 4500 and 4770 Kcal, which shows that cooking with dried wood is more efficient and convenient than cooking with wet wood.
Table 1. Wood and charcoal in terms of energy
|
Calorific value |
Useful energy |
Useful energy |
Diff. |
|
Wood |
Wood (8%) |
Charcoal (28%) |
|
|
3500 |
280 |
420 |
140 |
|
4500 |
360 |
420 |
60 |
|
4770 |
381 |
420 |
39 |
Table 2. Water boiling on various stoves
|
Type of stove |
Heat used (%) |
Theoretical saving of wood (%) |
|
Three-stone stove |
12.76 |
0 |
|
Madagascar Nigerian |
18.05 |
30 |
|
Improved metallic |
29.13 |
55 |
|
Improved ceramic |
31.85 |
60 |
If, on the other hand, a carbonization yield of 30 percent and a thermal energy yield of charcoal of 40 percent in use are obtained, wood must be used with a 25.7 percent yield so that it will be just as advantageous to use wood as to use charcoal, considering woods with a calorific value of 3500 Kcal. With woods of 4500 and 4770 Kcal, these limits of yield become 20 and 18.8 percent, respectively. Such high efficiency is seldom if ever achieved in burning wood for domestic use.
In recent years, various projects aimed at reducing the consumption of fuelwood have come into being in Africa. The campaign for improved stoves originated in programmes for checking unrestricted woodcutting and controlling desertification. Programmes for the spread of improved stoves are therefore an important aspect of forestry policy, especially in dry zones.
Improved stoves have raised hopes but have also generated controversy. This is understandable because there are so many different elements in the utilization of a stove by a housewife, beside the fact that the "housewife" herself is not a homogeneous unit of measure.
Two main questions interest us here: How really effective is the traditional three-stone fire? What improvement do the various improved stoves bring about?
Sylvain Strasfogel (1984) reporting on the results of work carried out by aid organizations working in Ouagadougou, Burkina Faso, emphasized the following points:
· models of massive stoves with chimneys are ineffective mainly because housewives cannot use them efficiently because of their lack of flexibility;· only movable improved stoves, metallic or ceramic, show a certain amount of efficiency.
In connection with movable stoves, laboratory tests on water boiling give the results shown in Table 2.
These results do not challenge the greater efficiency of charcoal. In fact, the 12.76 percent of the yield of the three-stone fire in the laboratory tests can be reasonably reduced to 8 percent in its actual use; that is, it shows about a 40 percent loss when compared with the laboratory's ideal conditions. It seems evident that better wood stoves (such as the improved ceramic one) would seldom attain a 20 percent yield.
Supplying wood or charcoal to rural users does not usually require transport over long distances, but that is not always true in supplying urban areas. Considerable energy, often of petroleum origin, is required in the transportation of fuel from the producer to the consumer. Our energy budget must also take this outlay into account. The general expression of the equation is simple: i.e. the energy used for transporting wood or charcoal should be less than the energy transported.
As populations grow and urbanization continues to increase, urban fuelwood needs will also grow... with significant implications for the management of forest resources.
The transport of wood or charcoal to towns in Africa is usually provided by old trucks (a certain amount is carried by man, by bicycles and by carts). It is difficult to determine the average conditions of use of such vehicles, so let us use instead the example of transport by an organized structure with a fleet of trucks for transporting both fuels. The trucks of the Forest Management and Production Operation, of the Water and Forest Service of Bamako, Mali consume an average of 37 l of fuel per 100 km and carry an average of 16 steres of wood per trip. Under such conditions, the energy transported is 3500 Kcal/kg × 325 (kg per stere) × 16 steres = 18.6 × 106 Kcal. Applying the coefficient of 8 percent thermic yield reduces this to 1.48 × 106 Kcal of useful energy for cooking.
The energy used for transport is equal to 
. The two quantities of energy are equal for a 400-km run, but as the vehicles always travel one way empty, the maximum carrying distance is halved to 200 km. Beyond that, therefore, more energy is spent than the wood being transported will yield. This distance, moreover, is very optimistic, because average truck consumptions of 75 l of fuel per 100 km are reported, which reduces the supplying distance to 100 km. It follows that by improving the thermic yield of utilization the supply distance can be lengthened.
In the case of charcoal used with a 28 percent yield, the energy consumed for transportation and the energy transported equalize at about 2000 km, that is, a supply distance of 1000 km. In improving the utilization yield of charcoal to 40 percent, it can be transported over 3000 km, a possible supply distance of 1500 km. The results are beyond comment: charcoal makes it possible to go much greater distances for the domestic energy needed by African towns.
In non-petroleum producing countries with large centres of population - such as Senegal and the Sudan - the use of charcoal rather than wood makes it possible to reduce greatly the petroleum cost for transport. Take Dakar, Senegal, for example, a city of more than a million inhabitants where about 100000 tonnes of charcoal was used per year in 1979-80, 95 percent of which was transported by truck.
Estimating 16 percent as the general average yield of carbonization in Senegal (Otchun, 1983), 95000 tonnes of charcoal transported by truck can be said to be equivalent to 593750 tonnes of wood, meaning 1826923 steres of wood (1 stere = 325 kg). If this amount of wood were to travel in the trucks of the Water and Forest Service of Mali, it would add up to 114182 truck loads over an average distance of 400 km. This in turn, would amount to a consumption of 16899036 l of fuel, or nearly 6 percent of the total Senegalese consumption of petroleum and gas oil for 1978.
Actually, the consumption of fuel would be higher because, as has been said earlier, trucks often make the outward journey empty.
Under the same conditions, transporting 95000 tonnes of charcoal calls for 3515000 l of fuel (truck carrying four tonnes of charcoal on average). This amounts to five times fewer petroleum products consumed on me road.
The current prices of wood and charcoal favour the use of charcoal by urban consumers. In fact, in terms of useful energy, the charcoal calorie is cheaper than the wood calorie.
For example, in Ouagadougou in 1979 the price of 1 kg of wood was CFAF 14 and the price of 1 kg of charcoal CFAF 60. If the Ouagadougou charcoal consumer uses this product with a 28 percent thermal yield, the calorie will cost (60/ 7,500 × 28 percent) = CFAF 0.028. On the other hand, the calorie derived from wood will cost (14/3,500 × 8 percent) = 0.05, that is, almost double.
Here is another example:
In Senegal, charcoal prices are, set by the government. The Department of Forests reported that in 1978 prices in Dakar were CFAF 70 for 1 kg of wood, and CFAF 25 for 1 kg of charcoal. In this case, the calorie derived from charcoal is even cheaper. However, this is really abnormal because the value alone of the wood used for making the charcoal is CFAF 125, assuming a carbonization yield of 16 percent and the actual cost of the wood as CFAF 20 per kg. In such a case me consumption of charcoal constitutes an enormous subvention from me forest to the consumption of energy in Dakar.
This is another important problem which cannot be elaborated here; however, two things should be highlighted:
· if the price of charcoal came closer to the actual costs of production (at least the price of the wood necessary to make it), charcoal imported from a distant area would become competitive, making it possible to organize charcoal trade between high forest zones and savannah and Sahelian zones. According to an FAO study in 1983 (Otchun), 1 kg of charcoal made in Côte d'Ivoire and transported to Dakar would cost CFAF 114 in Dakar;· even in countries where charcoal prices are not fixed by the government, there is still monopoly control by the transporters and truck owners. This situation is not profitable to the charcoal-maker, who is in fact usually a farmer doing this job during the dry season. Charcoal-makers should perhaps be organized in cooperatives so that they could benefit more, both from their labour in charcoal-making and from me utilization of their wood resources. In one way or another a share must be given to farmers to interest them in me management of the forests.
TRUCK TRANSPORT OF FUELWOOD how much energy is required?
Summarizing, it can be said that:
· from the energy point of view, charcoal as a fuel has a higher efficiency than wood as long as the useful thermal yield of wood is lower than 20 percent;· from the point of view of the national community, charcoal is still the most economical energy, even above the 20 percent thermal yield of wood, if long distances are involved in getting the fuel to the consumers;
· it is necessary to dissociate the problems of towns from those of the countryside. The use of charcoal in towns can be encouraged on condition that production is organized and distributed geographically in order to maintain the sustainability of the resource and if charcoal is used domestically. There are, moreover, other advantages that have not been mentioned here: charcoal causes less pollution of the atmosphere, less smoke, is easier to store, and so on;
· the utilization of charcoal will make it possible to increase the value to the countryside of its forest production (value of standing wood, cutting, carbonization), provided that the price of charcoal is allowed to rise to its proper level in relation to wood;
· to compensate for such a price rise, even more economical types of stoves must be developed to increase thermal yields and thereby reduce household fuel requirements.
Any saving of energy has an effect on forests and the environment, especially in large towns where high concentrations of people result in overexploited forest resources. Similarly, the possibility of obtaining charcoal from farther afield can also lighten the pressure of people on forest resources near the urban areas.
The decision to promote the use of charcoal instead of wood would not lead to uniform changes of forestry policy in the various sub-Saharan African countries because they do not all have the same climatic conditions, nor are they endowed, with the same forest resources. But policy changes might include the following:
· priority ought to be given to the management of existing resources. Their utilization could serve to meet the needs of urban populations in any part of their national territory. This provides an incentive to governments to protect and manage all their forest resources;· in some cases, forest resources outside national frontiers could be tapped;
· with regard to energy reforestation for large towns, the choice of locations could give more consideration to climatic and soil conditions than to criteria of proximity of consumption areas. This would give foresters greater flexibility in the setting out of woodlots in favourable zones. Under such conditions, these plantations would be considered as viable economic enterprises;
· agroforestry and protection forestry would be developed in zones where neither species nor adequate techniques for establishing woodlots as yet exist. Thus, for example, the management of forests and plantations in humid savannah zones for supplying towns of the Sahelian zone could be carried out;
· organization of the transfer of resources would be one of the important elements of the forestry policy of a country with suitable and unsuitable zones for forest production, even though this execution would not be solely a forestry enterprise. Other more efficient economic agents should intervene. Exploitation of production zone resources should generate more resources capable of assuring the continuance of operation; this would confer a great responsibility upon foresters.
To carry out this policy the following activities should be intensified or initiated:
· perfecting and distributing improved charcoal stoves. The cornerstone of all energy-saving policies should be me saving in me use of the resource itself. It is here that the impact is generally most significant;· improving carbonization yields. This is the second important element in saving fuel. Appreciable results can be rapidly obtained because this activity is directed at a more limited number of agents - the charcoal-makers - whose training thus becomes much easier. A 40 percent yield of stoves combined with a 30 percent yield of carbonization achieves a utilization of more man 25 percent of the total energy. Therefore, the training of charcoal-makers should be a priority activity of forestry administrations;
· setting up an efficient charcoal trading system. Forestry departments could encourage the formation of cooperatives and groupings of charcoal-makers which would make it easier to get bank credits for financing transport equipment and expansion;
· organizing regional cooperation to facilitate transfers across national frontiers. This is vital. Forestry administrations of the countries concerned should be reciprocally informed at all times about the situation of resources, supply and demand, and prospects envisaged. This is necessary to enable them to adjust their support activities to the transfer of resources.
The major forestry problem in Africa south of the Sahara today is the supply of domestic energy to the majority of me population. It will be so for a long time.
For the reasons discussed above, increased use of charcoal instead of wood in urban areas could promote charcoal to the rank of an exchangeable product within the framework of long-distance trade, with important consequences for the management and administration of the forests of the entire continent. Careful investigation and planning will be needed, especially in those areas where charcoal is not now the usual fuel.
OTCHUN, B. 1983 Etude sous-régionale des possibilités d'exportation de charbon de bois des pays riches en ressources forestières vers les pays déficitaires en Afrique centrale et occidentale. FAO Consultation Report.
STRASFOGEL, S. 1984 Diffusion massive des foyers améliorés au travers des unités locales de production et de distribution, le cas des foyers améliorés en céramique. Bois de feu, Informations de l'Association bois de feu, No. 11.
