Reafforestation in East Africa - Exploration of the potential of energy forestry

The attached note has been prepared by the Delegation of Finland as background material for discussion under Item 3 (b) at the DAC Meeting with Arab aid agencies, to be held on 18th-20th June 1980 in Paris.

Reafforestation in East Africa - Exploration of the Potential of Energy Forestry


1. Introduction

During the recent decades, most of the reafforestation activities carried out in East Africa have had a clear production objective: to find suitable species and methods for cultivating abundant and high-quality raw material for the expanding timber industry, and also for the pulp and paper industry expected to be established later. This work has resulted, for instance, in those high-yielding exotic pine forests found nowadays in many sites around the East African Highlands (1).

Besides production, forestry in Sub-Saharan Africa also has another objective: protection. This includes preserving water supplies, preventing soil erosion, and maintaining climatic conditions suitable for agricultural production (2).

The plans for the future role of the forests have now changed. This is due to the abrupt increase in the fossil fuel price, which took place during the 1970s. Especially in the industrialized countries, the growing trees are again seriously regarded as an energy source, and investigations into the possibilities of rationalized energy forestry have been started (3).

The concept of energy forestry is by no means a new one in the developing countries. Today, for instance in Tanzania the utilization of wood for fuel is 1,8 tons/capita/year, the fuelwood proportion is 96 per cent of the total timber consumption, and the population percentage using fuelwood is 99 (4).

The demand for firewood and charcoal instead of the more expensive kerosene and oil has already led to the increased forest and shrub destruction (5). This problem could be solved by special forest plantations for fuel (6). "Naturally there are institutional problems which impinge on agriculture and other practices of the society, but if such countries are to achieve even a modicum of internal fuel production, they should seriously consider such biomass systems and set up fuelwood plantations as soon as possible" (5).

Apart from local fuelwood plantations, energy forestry may in the future, offer also other possibilities for the East African energy economy. Let us mention as an example, the plans from the Philippines and from India to generate domestic electricity by means of fuelwood-driven steam power stations (7,8). Another future possibility is the production of liquid fuel, mainly methanol, using wood biomass as a feedstock. The large surface areas of the Sub-Saharan countries together with a suitable climate favour this kind of production systems in the future (9).


2. Energy farming

Energy farming is a discipline of cultivated plants and husbandry in which the solar radiation is collected and converted into biotic energy of the phytomass. The aim is to obtain high energy yields by selecting, breeding and raising fast-growing crops.

Promising results have been achieved in the Nordic countries with the willow (Salix) (9). Special energy willow farming techniques have been developed to maximize the net energy returns from farming. It is based on the following principles:

• the energy willow is propagated clonally using cuttings. This assures the genetic homogeneity of a developed high-yielding clone,
• the crop is grown in a density much higher (20000 - 70000 sprouts per hectare) than in conventionally established forests. In such stand, weeds do not survive due to the shading effect, and the solar energy binding is at its highest,
• the whole-tree harvest is applied, possibly without leaves. The stems are dried over the next growing season in a stock-pile and then chipped,
• the next crop grows by coppicing. This also increases sprouting and makes the stand still denser.

In the short Nordic summer, dry matter yields of about 20 tons per hectare can be collected, in energy equivalents about 350 Gigajoules. About one per cent of the annual incoming solar radiation is converted into biotic energy.


3. The East African potential

Many features in the above-mentioned energy farming principles can be adapted to East African conditions if suitable species can be found. In fact, the abiotic growth circumstances allow much greater potential than is the case in the temperate zones.

Clean-weeding, especially for the grasses, is one of the most laborious tasks in savannah reafforestation (10). This usually takes two to three years after planting. With high densities and coppice regeneration, the need for clean weeding is essentially diminished.

The definite alteration between dry and rainy seasons can be utilized in practical husbandry. During the rains one lets the crop grow. When the dry season comes, the soil hardens to permit harvesting. If the stems are cut at the beginning of the dry season, the crop will dry by the onset of the rains. The stock-pile year in the Nordic system can be avoided.

Coppicing culture helps soil conservation. In a conventionally grown pine forest, the critical erosion period is between the clear-cutting and the establishment of the new stand by planting (11). In coppicing species, the stump and the roots tie the soil particles together. The risk for erosion during the heavy rains is strongly reduced.

The East African climate and soils would allow dry-matter yields of 30-40 tons per hectare per year given the same solar energy conversion efficiency that is possible in the temperate zone.


4. Possible species

The altitude and rainfall pattern divides the East African countries into different ecological zones. They all offer different requirements for the possible species. Fortunately, plenty of afforestation trials using different species have been undertaken in a variety of environments. The basic information on the behaviour of different species is thus already available.

Eucalyptus trees have grown the most productive fuelwood plantations in East Africa. Height increments of 2,5-3,0 meters per year are not uncommon during the first ten years (12). Annual volume increments of nearly 60 m3 /year/ha have been recorded (11) and the biggest standing volume figure in a planted forest is as high as 2300 m3 /ha (13).

Eucalyptus plantation must be established through direct seeding or preferably through pot planting (10). The establishment is not possible clonally by normal cuttings. This feature raises the establishment cost. The coppicing ability of Eucalyptus is high and the stands are well suited to combat weeds.

Over 100 Eucalyptus species have been screened in various savannah types in different countries. Three or four of them are recommended for dry tropical and semi humid tropical environments.

Gmelina arborea has now an established place in the plantation programs of many African countries, particularly in Sierra Leone, Nigeria and Malawi (15). It is thus suited to a humid tropical climate, needs a fairly high rainfall (1750-2000 mm per year is regarded as the optimum), but also a definite dry season.

The crop is easily established by stump raising (root and shoot cuttings) and coppices well. Gmelina is typically a short-lived tree and the rotation time in conventional forestry is under 15 years.

Cassia siamea was formerly one of the most widely planted and successful exotics in many African countries. Extensive plantations were made in Ghana, Nigeria, Zambia, Tanzania and Uganda. It has now to a great extent been displaced by Eucalyptus which grows faster. However, Cassia has two advantages over Eucalyptus: it is relatively resistant to termites (10), and it is possible to establish clonally by stump raising. Cassia also coppices well, and present plantations are commonly worked on rotations of only five to eight years.

Bambusa vulgaris (''Golden bamboo"). Little has been done systematically to explore the potential of bamboo plantations in African savannahs. Golden bamboo is a comparatively recent introduction to Africa and is found in Gambia, Ghana, Uganda, Tanzania and Mauritius.

Bamboo is propagated clonally by cuttings, it coppices well, and dense stands are easily established given careful soil preparation and tending during the rooting period. Harvest cutting is done by a selection method, by removing 50 per cent of the standing material on a cycle of two to three years (15).

Bamboo has been described as the poor man's timber and has a wide range of uses starting from poles and ending in the high-quality paper industry. We already know the growth vigour of bamboo and the species needs attention also in the investigations of energy forestry.

Of course, there is a variety of other coppicing species for Sub-Saharan energy forestry. The screening of all possibilities is easy but a time-taking task. Moreover, when the concept, principles and goals of energy forestry have been widely accepted, modern plant breeding is well equipped to produce still more suitable clones.


5. Conclusion

The search for new energy sources goes on all over the world. Renewable energy sources are particularly important and here the green plants offer a multitude of possibilities. This is the case especially in the developing countries.

The surface area receiving solar radiation is large in many of the Sub-Saharan countries. The climate is suitable, in some places ideal, to high biomass production. The labour-intensive links in the production chain may be easier to carry out in the populated East African countries than in the industrial world.

As a whole, the concept of energy forestry for developing countries is a combination of traditional, conventional fuelwood forests and special energy plantations. Local fuelwood plantations are certainly needed at the village level to overcome the problem of increased kerosene price. Special energy plantations offer a new possibility to farmers. The rotation time is strongly reduced from conventional forestry. It might be easier for the local farmer to accept a growing time of one to three years than the time from ten to thirty years.

The potential of energy forestry should now be explored in the East Africa conditions. The experiences from the general principles and methods applied in the Nordic countries could be exploited and serve as a basis in planning trials and tests for different plants, husbandry methods, harvesting and energy extraction procedures.


6. References

1. L. Berry, Forestry, in Tanzania in Maps (University of London Press 1975), pp. 68-70.

2. M.L.S.B. Rukuba, Forestry in Uganda, in East Africa: its Peoples and Resources, ed. W.T.W. Morgan (Oxford University Press, 1972) pp. 221-228.

3. Siren, Goals, Means and Results of Energy Forestry. Manuscript in the Swedish Agricultural University, 1980.

4. M. Slesser and C. Lewis, Biological Energy Resources (E & F N Spot Ltd London, 1979).

5. D.O. Hall, World Biomass: an Overview, in Biomass for Energy, Conference(C20) at the Royal Society, UK, 1979.

6. Floor, W.M. The Energy Sector of the Sahelian Countries, Policy Planning section, Ministry of Foreign Affairs, The Hague, Netherlands, 1977.

7. E.N. Terrado, (with P.V. Bawagan &  J.A. Semana) in Sun: Mankind's Future Source of Energy, ed. F. de Winter (Pergamon Press, New York, 1978), pp. 101-105.

8. C.V. Seshadri, et al. Energy Plantations - a case study for the Coromandel littoral, MC Research Centre, 11/12 North Beach Rd., Madras 600001, 1978.

9. V. Pohjonen, et al. Biotic Solar Energy, Manuscript in the Finnish Forest Research Institute, 1980.

10. Tree planting Practices in African Savannas, FAO Forestry Development Paper No, 19, Rome 1974.

11. B. Lundgren, Soil Conditions and Nutrient Cycling under Natural and Plantation Forests in Tanzanian Highlands, Rep. in Forest Ecology and Forest Soils No. 31, Swedish University of Agricultural Sciences, Uppsala, 1978.

12. J. Borota, The Growth of the Tree Species in Lushoto Arboretum.Silv. Res. Note Tanz., 70, 1971.

13. G. Lysholm, The oldest Eucalyptus microcorys stand in Tanzania. Silv. Res. Note Tanz., 14, 1970.

14. A.F.A. Lamb, Fast Growing Timber Trees of the Lowland Tropics. No. 1. Gmelina arborea. Oxford, Commonwealth Forestry Institute, 1968.

15. J.  Goulez, Creation des bambusaies á Bambusa vulgaris sur sols de savana au Congo-Brazzaville. Proceedings of the World Symposium on Man-made Forests and their Industrial Importance, 3:1603, FAO, Rome 1967.

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Later comment, 29 Mar 2020. Mr David Johansson from Finnida invited me to this Paris meeting (6 Jun 1980) to present ideas of modern energy forestry that would be applicable to later promote through development co-operation.

Jälkikommentti, 29.3.2020. Kehitysavun yksikkömme Finnida johtohenkilö David Johansson kutsui minut mukaansa tähän Pariisin kokoukseen (6.6.1980). Pidin kokouksessa esityksen energiametsätalouden uusista mahdollisuuksista, Suomen ja muiden Pohjoismaiden 1970-luvun kokemusten perusteella. Uusia mahdollisuuksia oli myöhemmin harkittava käytettäväksi Suomen antamassa Afrikan kehitysavussa.