|CERES No. 072 (FAO Ceres, 1979, 50 p.)|
- forest destruction
In the past few years, there has been a growing realization that charcoal is a much more important source of energy than generally acknowledged. Until recently, estimates of global consumption were never higher than 5 million tons a year; now FAO experts say roughly 30 million tons of charcoal are used a year in both the domestic and industrial fields. The fact that charcoal is a favoured urban domestic fuel suggests that charcoal use is rising much faster than fuelwood use, since population growth is much higher in urban areas than rural areas.
Charcoal is in many respects a highquality fuel. It has twice the heat value per unit weight as wood, and it is much more energy efficient in application. Therefore, it can be transported economically over longer distances. It produces no smoke or tar and it cannot deteriorate in storage.
In addition, charcoal has a wide range of use as an industrial fuel. Colossal amounts are utilized in Brazil and Argentina for steel making, while in northeast Uganda charcoal is used in lime and cement manufacture. Other uses occur in drying, water purification and sewage works. Large numbers of rural families depend on commercial production and marketing of charcoal as a source of income.
But because between 50 and 70 per cent of the heat value is lost during conversion from wood to charcoal, it may be more efficient to use fuelwood where transport distances are short and costs are low. The balance between fuelwood and charcoal, and the limits of economic supply for the latter, depend on production costs, transport costs and market prices of charcoal and alternative fuels. In a recent study in East Africa, it was found that fuelwood was more attractive up to a road distance of 82 km, and charcoal beyond that distance.
Since up to 8 kg of wood are needed to produce 1 kg of charcoal, often the effect of charcoal production is to extend greatly the area of forest destruction. The damage has been worst around large towns in Africa and Asia.
Yet charcoal manufacture remains a logical way of using wood that otherwise would be too costly to transport. "There's no escape," says Mike Arnold, an FAO senior forestry planning officer. "There's no other economical alternative. Countries simply have to control the situation and produce charcoal in a less destructive way."
The bulk of the charcoal produced in the world is made in ovens
called kilns, which are inefficient in their use of wood. Kilns have evolved
from the earliest means of making charcoal known to man, i.e., by covering
burning wood with turf or by firing the wood in a hole in the ground. Although
earth or pit kilns require very little investment, yield and quality of the
A variety of designs for brick and steel kilns have been developed, which not only have the advantages of simplicity, small scale, low costs and even portability, but also improve the conversion rate. An even higher conversion rate can be obtained using retorts, containers in which wood is heated externally until carbonization occurs. Since the capital cost of retorts is relatively high, they are generally used only in large-scale industry. However, retorts permit the capture of gas and distillable by-products, which can offset the costs of transporting the wood over long distances, thus providing employment for rural populations living near plants.
A small portable retort developed in Western Australia with a
production capacity of 1 ton/day offers a technology both intermediate and
appropriate for developing countries. At first sight, the capital required for
retort operations, large or small, appears to be
a barrier to their use in the developing world. A closer look shows that the initial high capital sum is usually compensated for by considerable savings in other directions. This becomes more important as labour costs increase.
There is a trend toward using eucalyptus plantations to provide wood for large-scale charcoal production, particularly in Brazil. Slower growing species of proportionately higher basic density can produce as much weight of charcoal per hectare/year as the faster, lighter species now used, while the resulting denser charcoal has distinct advantages in industry.
But since virtually all species of wood can be converted to charcoal, production can be based on the large volumes of wood other than commercial timber species, which are otherwise destroyed in land clearing or left unused in forests. Such a programme is under way in Uganda, where 20 000 tons of charcoal are made each year using only waste wood. Similar projects exist in Zambia and Ghana.
Such programmes and other efficiency measures must be implemented elsewhere, since there is often preference for charcoal even when wood or other fuels are cheaper. Burning wood for cooking purposes can make an already warm house intolerable, whereas efficient charcoal stoves, which can be made for as little as $1, generate very little heat. In addition, the smokeless fuel provides a solution to the pollution problems of some of the larger cities of the tropics. The benefits of using charcoal over smoky fuels in cities are not yet fully appreciated in developing countries but this factor could be important at a later stage, e.g., if clean air legislation were introduced.
In developing countries, it is often a lack of entrepreneurial skills that inhibits the development of more efficient means of charcoal production. The help of the government or aid agency is often missing in the early stages. But according to Arnold, at least an awareness of the problem of charcoal production inefficiency has grown rapidly over the past few years.