A.P. RobinsonA.P. Robinson is with the Overseas Development Natural Resources Institute, Oxford, UK.
The Bay Region of Somalia is the main charcoal production area serving the national capital and largest city of Mogadishu some 300-350 km away. Charcoal production areas are licensed by the National Range Agency to charcoal cooperatives and operated by cooperative members living in temporary camps.
An unusually efficient charcoal production method developed in the region forms the subject of this photo-story.
Unfortunately, however, nothing is being done to regenerate the trees used to make the charcoal, so that efficient production, in this case, is leading to steady resource depletion.
Charcoal is the major fuel for domestic cooking in Somalia's capital, Mogadishu, and other urban areas. Its industrial uses are relatively minor and exports are prohibited by law. Somalia consumed an estimated 80000 tonnes of charcoal in 1983, with Mogadishu accounting for over half of this with 42000 t recorded entering the city that year.
The country's charcoal needs are met by domestic production. Two manufacturing methods are used, one practiced in northern Somalia which is wasteful, and another practised in central and southern Somalia - the Bay Method - which is very efficient and accounts for some 80 percent of the entire production.
The natural forest in Somalia constitutes a very small proportion of the total land area and is little exploited for charcoal. By far the largest resources for charcoal manufacture are the woodlands and wooded bushlands which comprise just under half the total land area. A substantial proportion of this vegetation is situated in the Bay (pronounced "by") Region, 300-350 km west of Mogadishu. The region has adequate road access and has developed as the main charcoal production area serving the capital, the country's largest market. This was the area chosen to carry out the study of the local manufacturing method, consequently named the Bay Method.
This evaluation of the Bay Method of charcoal production formed part of the wider techno-economic appraisal of the charcoal industry in Somalia carried out under British technical cooperation through the Overseas Development Administration in collaboration with the National Range Agency (NRA), Government of Somalia. The performance of the Bay Method was compared with the transportable metal kiln of the Overseas Development Natural Resources Institute (ODNRI). This has found widespread application in land clearance and reafforestation schemes in less developed countries.
The 14-month assignment was undertaken by the author during 1983/84 and augmented by a ODNRI economist. The overall study made an in-depth examination of the industry and an assessment of the various charcoal-making technologies.
Charcoal production is carried out at 66 camps situated in and around the Bay Region. Each camp is managed by a member of the Charcoal Producers' Cooperative, and only those members and their workers are legally allowed to manufacture charcoal. To establish such a camp a licence is required from the National Range Agency (NRA) - set up to develop the country's rangelands to work a given area. A representative from the NRA visits the selected site with the cooperative member, and boundaries for a 25-km2 working area are loosely agreed, although no physical demarcation takes place. A charcoal-makers' camp, centrally situated on site, is organized.
The cooperative member manages the logistics of the camp and arranges the transport and sale of charcoal. He normally resides in a nearby town or village, and oversees the charcoal operations. Each camp contains a settlement of around 14 workers and their families. Dwellings of small round huts are made using the traditional methods practiced by the nomads. The camps are fairly remote and there is no transport. There is usually no natural water-supply and water, contained in 200-litre empty oil drums, is brought in by the trucks that come to collect the charcoal. Food and other supplies arrive in the same way. The charcoal workers and their families remain in the area until the usable timber is exhausted - normally two years or so - before moving on to a new site.
The charcoal operations in the camps are well organized. A foreman is elected from the workers to arrange the day-to-day work and to negotiate with the cooperative manager. The workers, either individually or sometimes in twos and threes, select an area to work within the boundary of the charcoal camp site and they cut timber to build a kiln. When sufficient timber has been cut, the foreman organizes the rest of the camp workers to help collect the timber, build and operate the kiln and, when ready, unload the charcoal and load the truck and trailer.
Consumer preference is for dense charcoal, and the main and preferred timber species used is Acacia bussei, locally named galol. Only the larger, and consequently denser, trees are selected. Workers rarely fell trees below 15 cm in diameter. Both healthy and dead or dying trees are felled. Another species used, but in far smaller quantities, is A. senegal, locally named adad. Both these species coppice well. However, regrowth is often effectively destroyed by browsing camels and other livestock and rarely stands more than 5 cm high. No protective measures are taken by the workers to protect this regrowth. Stumps are sometimes burned to clear tracks for donkey carts and the charcoal trucks. The result is that the resource is diminishing. As the trees reach maturity they are felled and no effective regeneration or replanting takes place. This matter requires urgent attention, as an integral part of the charcoal scheme, which must consider the resource base as well as the techniques of charcoal-making.
Figure 1. Felling large Acacia bussei
Timber is felled and cut to length by axe. No other cutting instruments are employed. The axes are made by local blacksmiths shaping the axe-head from heavy-duty vehicle leaf springs. The hardness of A. bussei quickly blunts the axe which requires frequent sharpening by file.
When sufficient timber has been prepared to build a kiln it is collected by donkey and cart and taken to a central site near the site where the timber was felled. Donkey-cart travel is kept to a minimum and the furthest distance covered was, in the case of the evaluation trials, 200 m. Donkey-cart loads are typically 250 to 300 kg.
Figure 2. Axing timber to length
The tree is normally axed as close to the ground as possible. Stump height is around 20 cm which represents less than 5 percent of the total raw material. After felling, the timber is cut into approximately 125-cm lengths, suitable for loading on to a donkey cart. Trunk diameters range from 15 to 90 cm. Practically all the branch wood is used. Only the small branch wood of 3 cm diameter and less that contains thorny twigs is discarded.
Generally the kiln capacity ranges between 10 and 35 t of air-dry timber. The kiln is built by stacking the timber upright on the soil floor. The timber is stacked into a circular mound two tiers high at the centre, with the larger pieces making up the lower tier. It is packed as close as possible and the gaps are filled with smaller pieces of wood.
When the stacking is complete the timber is covered with metal sheets made from 200-litre empty oil drums. After removing the top and base the metal cylinder is cut open and flattened into a sheet. Two types of drums are used: a thin walled one approximately 1.5 mm thick, and a 2.5-mm thicker one. The latter is preferred by the charcoal-makers but is becoming less available. From information supplied by the workers it is estimated that the thin sheets have a useful life of around four to five kiln operations while the thicker sheets last for 15 or more operations. The sheets are placed over the timber stack and overlapped so that the edge of the lower one is underneath the edge of the sheet above it.
Figure 5. Metal sheet covering
A height of approximately 125 cm above the ground around the stack's circumference is left uncovered. A skirt of thorny branch wood is placed around it. Starting at the base of the skirt and working upwards, soil is placed over the thorny branch wood and metal sheets, forming a covering of approximately 5 cm thick. Deep red in colour and very fine, the soil is locally named hargen. The preferred type contains a fine root system which holds the soil together in clumps. Soil without this root system tends to fall through any gaps in the metal sheet covering.
To light the kiln a worker climbs to the top and removes part of the soil and some of the upper sheets to gain access to the timber charge. A small fire is then built on top of the charge. After a few minutes the top sheets are put back in place and recovered with soil. Holes approximately 10 cm in diameter at intervals of approximately 100 cm are made through the soil covering the thorny branch-wood skirt to allow air to enter and smoke to exit. On larger kilns of 20-35 t air-dry timber capacity, holes are also made in the upper section of the kiln.
Charcoal occupies about half the volume of the wood that produces it and consequently as the wood turns into charcoal the kiln shrinks in size. The workers watch the kiln closely to ensure that the metal sheet and soil covering are kept intact for they know that soil falling through the metal sheets will cover the timber beneath it, producing brands pieces of partially carbonized wood. They are also aware that excess air entering the kiln causes the wood to burn to ash and reduces the charcoal yield. As the kiln shrinks the movement can cause soil slippage and its steep sides often have to be supported with pieces of timber. The size and number of holes around the thorny branch-wood skirt allowing air to enter the kiln and smoke to exit are adjusted according to wind conditions and progress of the run. The carbonization process takes four to ten days, depending on the kiln size and condition of the timber.
The zone of the fire travels down through the timber charge until it finally reaches the lower air inlet/smoke outlets. On the larger kilns, when the fire zone first reaches the upper inlets/outlets they are closed. When the thorny branch-wood skirt catches fire, the carbonization of the timber charge is considered complete and the kiln is sealed for cooling. The remains of the thorny branch-wood skirt are removed and the kiln, sealed with soil so that no air enters, is allowed to cool for about ten days.
The soil and metal sheets are removed. The charcoal stack is then dismantled and the charcoal is spread out over the ground. Any fires are isolated and extinguished by covering with soil. A watch is kept on the freshly made charcoal for 24 hours in case of further fires.
Figure 8. Cooled kiln opened and charcoal exposed
Any brands are collected and a small kiln is built nearby using the same techniques described above. The kiln is fired and the carbonization period is normally less than 24 hours. Cooling of this kiln takes only two days.
The charcoal is transported by truck and trailer. The workers clear an access road to the opened kiln so as to load the charcoal directly on to the vehicle parked alongside, thereby reducing handling breakages. Wicker baskets and forks are used for loading. The larger pieces of charcoal are carefully stacked around the outer walls of the truck and trailer so that the main bulk of charcoal can be tipped inside. Charcoal produced from Acacia bussei has exceptional strength and the outer walls of charcoal need only be supported by wooden posts 7 cm in diameter spaced 30 cm apart. Using this method, the charcoal can be stacked 3 m high. Typical loads are: truck 12 t; trailer 15 t.
Figure 9. Loading charcoal on to the trailer
The truck and trailer, once fully loaded,. depart for Mogadishu. The distance from the charcoal camps to the capital is 300 to 350 km. The condition of the tarmac road between the camps and Mogadishu is very poor in places and the journey takes about 12 hours, normally spread over two days. Charcoal losses on this journey are negligible. Charcoal manufacture continues during the rainy season, but shortages can occur in towns if bush tracks become impassable.
Figure 10. Truck and trailer: 27 t of charcoal
On arrival at Mogadishu the vehicles travel to the weighbridge. Here the unladen weight of the individual truck and trailers have been previously registered. Laden with charcoal, they are weighed and by deducting their unladen weights, the quantity of charcoal is known. In 1983, over 42000 t were recorded entering the city.
From the weighbridge the truck and trailer travel to one of the numerous Mogadishu charcoal stores, all of which are controlled by the Charcoal Marketing Cooperative. Unloading is carried out simply by pushing the charcoal off the truck and trailer on to the ground outside the store. It is then carried inside in wicker baskets. An effective means of quality control is in force. If the keeper of the charcoal store, a member of the Charcoal Marketing Cooperative, is not satisfied with the quality of charcoal he can lodge a complaint with the Charcoal Producers' Cooperative. His dissatisfaction may be that the charcoal is not fully carbonized or contains a high proportion of small pieces. The Cooperative will send representatives to visit the store and inspect the charcoal. If the storekeeper's complaint is upheld then the charcoal camp-owner and workers are penalized and the storekeeper compensated. These penalties, in the form of a reduction in the payment the charcoal camp receives for that unsatisfactory batch, are quite substantial. For this reason, charcoal camps take particular care to see that the product they supply is of reasonable quality. Charcoal fines small pieces of charcoal - from the stores are sold to the limestone cooperatives for use in shaft kilns to manufacture lime. It was noted that charcoal fines from stores even as far away (250 km) as Baidoa are transported to Mogadishu for this purpose.
Table 1. Carbonization data
|
|
Average timber moisture content (wet basis) |
Weight of timber in kiln (air-dry basis) |
Weight of timber in kiln (oven-dry basis) |
Carbonization time |
Cooling time |
Weight charcoal produced (oven-dry basis) |
Weight brands produced (oven-dry basis) |
Efficiency of conversion (timber to charcoal w/w oven-dry basis) |
|
% |
kg |
kg |
days |
days |
kg |
kg |
% |
|
|
Local kiln |
||||||||
|
Trial No. 1 |
17.4 |
14088 |
11637 |
3.6 |
12 |
4791 |
0 1 |
41 |
|
Trial No. 2 |
24.5 |
31751 |
23972 |
8.4 |
9 |
10056 |
1514 |
42 |
|
Trial No. 3 |
24.7 |
15529 |
11693 |
6.2 |
10 |
4589 |
- 2 |
39 |
|
Transportable kiln |
||||||||
|
Average of six trials |
22.6 |
2681 |
2077 |
1.0 |
0.7 |
739 |
57 |
36 |
1 A thorough search through the charcoal revealed no brands.2 Weight of brands not measured but estimated to be in the order of 500 kg.
NOTE: Representative timber samples were measured for: moisture content using the standard oven drying to 105°C-110°C; and density using the method specified in TAPPI Standard T18 M-50. Representative charcoal samples were collected from each trial and charcoal analysis of ash, total volatiles, fixed carbon content, moisture content and calorific value were carried out at ODNRI using British Standard 1016, Part 4 as a guide. Timber analysis of ash and calorific value were also carried out at ODNRI. Details of these and charcoal bulk densities are given in Tables 2 and 3.
Table 2. Charcoal analysis
|
|
Moisture content (wet basis) |
Volatiles 1 (wet basis) |
Ash (wet basis) |
Fixed carbon content (wet basis) |
Gross calorific value (oven-dry basis) |
Bulk density (oven-dry basis) |
|
% |
% |
% |
% |
MJ/kg |
kg/m3 |
|
|
Bay kiln |
||||||
|
Trial No. 1 |
4.45 |
20.07 |
5.62 |
69.86 |
28.95 |
380 |
|
Trial No. 2 |
5.22 |
14.97 |
5.09 |
74.72 |
29.89 |
340 |
|
Trial No. 3 |
2.21 |
9.94 |
5.02 |
82.83 |
31.45 |
- |
|
Transportable kiln |
||||||
|
Average of six trials |
3.73 |
12.33 |
4.70 |
79.24 |
30.56 |
350 |
1 Volatile values are total volatiles minus moisture.
Table 3. Timber analysis
|
Timber species |
Local name |
Locality |
Density |
Moisture content |
||
|
Range (oven-dry basis) kg/m3 |
Average (oven-dry basis) kg/m3 |
Range (wet basis) % |
Average (wet basis) % |
|||
|
Acacia bussei 1 |
Galol |
Bay region |
722 to 1174 |
928 |
9-40 |
22 |
|
A. senegal |
Adad |
Bay region |
544 to 808 |
656 |
10-46 |
29 |
1 Ash (wet basis), 1.25 percent; gross calorific value (oven-dry basis) 19.30 MJ/kg).NOTE: Kiln temperatures were measured using stainless steel sheathed chrome/alumel thermocouples connected to a portable digital temperature indicator. The thermocouples were fed through metal conduits previously inserted into the upper, middle and lower sections of the kiln wall. These positions were not exact because of the shifting of the kiln as the timber charge reduced in volume during carbonization.
Three kiln trials were carried out using the Bay Method. As a control and comparison, trials using the transportable metal kiln were carried out using timber of the kind used in the Bay kiln trials. Transportable metal kiln operations were conducted using the standard methods described in the ODNRI Rural Technology Guide No. 12 Charcoal production using a transportable metal kiln. The timber, charcoal, and brands were weighed to the nearest 0.5 kg using a suspended weighing machine. Details of these weighings with carbonization data and efficiency of conversion are contained in Table 1.
The study has shown that the Bay Method is an efficient and appropriate means of producing good-quality charcoal with yields in excess of 40 percent (oven-dry basis).
The Bay kiln's efficiency was due, in some part, to the excellent charcoal-making properties of Acacia bussei. This was reflected by the fact that yields of 36 percent of good-quality charcoal were obtained using the transportable metal kiln, and compares to yields of 20-25 percent normally obtained with a variety of other species.
The felling operations using locally made axes were efficient, with stump wastage representing less than 5 percent of the total raw material. The somewhat unique method of loading and transporting the charcoal maximizes the carrying capacity of the truck and trailers, which avoids the use of sacks. Overall, the cost of the Bay Method of charcoal production was found to be comparable to that using the transportable metal kilns.
As mentioned earlier, although the preferred species of timber for charcoal production coppiced well, most regrowth was effectively destroyed by browsing animals. Since no protective measures were taken by the charcoal workers to safeguard the regrowth, the resource is diminishing.
The kiln's operational success and its high efficiency rely largely on the use of metal sheets in its construction. However, these are in short supply. Reducing the number of sheets used to build the kiln would reduce its efficiency. It is also important to have the correct soil conditions - similar to those described in this report - to avoid contamination of the charcoal by loose soil falling through gaps in the sheets. The Bay kiln requires considerable expertise in order to be built and operated efficiently and instruction in its use would involve comprehensive training. In view of this its introduction elsewhere is speculative and other methods of similar efficiency may therefore be adopted.
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