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Wood raw materials for pulp paper in tropical countries

P.J. VALKOMIES

P.J. VALKOMIES, a former member of FAO Forestry and Forest Industries Division, is Vice-president of H.A. Simons (International) Ltd., Consulting Engineers, Vancouver. He prepared this discussion paper for the second session of the FAO Committee on Forest Development in the Tropics, hold at Rome, 21-24 October 1969.

THE PURPOSE OF THIS PAPER is to record some thoughts and guidelines regarding the use of wood available in tropical countries for pulp and paper production. To that extent it deals with both natural and planted softwood and with hardwood species and bamboo, but excludes the, for the tropics, often important annual crop fibres and residues. The paper is intended to indicate what basic criteria tropical woods must meet in order to be accepted by the pulp and paper industry and what steps need to be taken by the forestry sector toward establishing what prospects tropical countries have to use their wood resources for pulp and paper production.

Basic considerations

It is obvious that a right combination of pulp and paper markets and wood raw materials is a prerequisite for developing new industries and establishes a basis for selecting the type and size of the development. While domestic or regional markets in the tropical countries are often relatively limited and can support a type and size of plant which would not be internationally competitive, these markets are often protected and can in some cases accept products which are not of the best quality. To be competitive on international markets, pulp and paper development normally needs large quantities of wood at relatively low cost. The type and quality of wood which a pulp and paper mill can use from the technical point of view and the price the mill can afford to pay for the wood vary widely depending on the market. The three basic and most important questions regarding the feasibility of using wood for pulp and paper production are thus:

1. markets for products;
2. type and quality of wood;
3. quantity and cost of wood.

Forecasting future markets is a well-established and relatively simple procedure which needs no further discussion within the scope of this paper.

Classifying the wood to be either coniferous or broad-leaved type is sufficient to indicate the broad pulp and paper categories for which it can be used. Regarding quality, an extremely important factor is uniformity of wood in terms of uniform density and uniform fibre dimensions. Other factors affecting quality are hemi-cellulose, extractive and parenchymatic and vessel cell contents in the wood. It should be noted that, while the softwood species have a wider and more versatile use for pulp and paper products than hardwood species, long-fibred softwood cannot be said to be of better quality than short-fibred hardwood without specifying for what product the wood is used and without considering product quality requirements and economics of operation.

The amount of wood available for any given year is important for establishing the initial and ultimate rates of development. However, it is by no means necessary to have available detailed inventory results to determine whether a certain wood resource may be used for pulp and paper production. Quite the contrary. Time-consuming and expensive inventories, which are particularly complicated in mixed tropical forests, can be justified only after a preliminary appraisal of the development has indicated that the proposed project may be technically and economically feasible.

Since it is important to know at an early stage the approximate cost of wood delivered to possible mill sites, preliminary management, planting or replanting, logging and transportation plans must be drawn up, and their capital and operating costs estimated. Particular attention must be paid to keeping the cost of wood as low as possible during the initial years of harvesting when a newly established mill passes through its economically most difficult period.

Other considerations

A large number of other factors also affect the technical feasibility and economic soundness of a pulp and paper development. While most of these requirements can normally be met, they are often very expensive in tropical countries. On the other hand, compensating factors such as low costs for wood or labour, subsidies, or protection duty, can offset these high expenses. But the most important factor is to locate a site for the industrial development. Land suitable for heavy industrial construction, electric power, labour and housing can normally be made available almost anywhere, but process water and transportation facilities are often difficult or expensive to establish and become the main criteria for selecting a mill site. Consequently the cost of wood and the economics of pulp and paper production are affected by the distance and cost of transporting or providing transport facilities for wood to or near the source of process water and for products from it. Since 4 to 6 tons of green wood are required to produce a ton of pulp or paper, an ideal location for a mill, from the point of view of transport, is normally the point of gravity of wood supply. Because tropical woods often have a high moisture and bark content, it is necessary to know what these are and how they affect transport methods and costs.

FIGURE 2. - A 13-year-old plantation of Pinus khasya in Chiengmai Province, Thailand. Recent laboratory tests have shown the wood to be suitable for producing high-grade pulps.

Softwoods

For practical purposes pines are the only tropic al conifers which need to be considered as raw material for pulp and paper. While limited in volume, the indigenous pines in any given area have reasonably uniform density and fibre dimensions and are thus good raw material for a wide range of pulp and paper products. It should be noted that, in terms of quality, pulps produced from these pines are similar to pulps produced from pines grown in subtropical and warm-temperate climates. This means that they produce pulps of higher tear but lower tensile and burst values than are typical for pulps produced from conifers grown in cold-temperate and arctic climates. Since the pulping characteristics of most of these pines are known, only limited laboratory pulp testing is normally needed for new developments.

Relatively little is known about the pulping qualities of exotic plantation-grown pines. It appears that, when climatic and soil conditions at plantations are similar to the native conditions of the pine, it produces pulp similar to pulp produced from indigenous trees. LOW altitude exotic plantations seem to produce pines which can have entirely different densities, fibre dimensions and resin contents from the indigenous trees, and these can vary even within the same plantation. To evaluate the pulping quality of pines grown in exotic plantations, it is thus necessary to determine carefully these variations and to carry out detailed pulping tests. It is also necessary to develop a long-term harvesting plant which secures a reasonably even mixture or a homogeneous heterogeneity of wood Supplied to the plant.

Because of the size of the trees and the markets available, it is common for tropical pines as well as hardwoods to be well suited to manufacture also lumber plywood and other such products. The effect of integrating pulp and paper production with mechanical wood-working industries should thus be evaluated.

Hardwoods

The vast majority of wood available in the tropics is in mixed stands of a Large number of broadleaved species. While transportation problems and costs are important obstacles against utilizing these resources, the main reason for the pulp and paper industry's very limited use of tropical broadleaved wood species is the wide variation of densities, fibre dimensions and other characteristics of the sometimes hundreds of wood species in a stand.

FIGURE 3. - Bamboo is used in substantial quantities in many tropical countries for pulp and paper production. Bamboo pulps carte be classified with superior hardwood pulps, and they have certain unique and desirable qualities for the production of fine papers.

The oven-dry density or specific gravity of these wood species vary from 0.2 to 1.2. Approximately one third of the species have a density outside, mainly above, the 0.3 to 0.8 specific gravity range normally considered suitable for pulping.

Fibre length is a poor criterion for evaluating the suitability of tropical hardwoods for pulp production. As a rule these, like other broadleaved species, have fewer and shorter fibres and more hemicellulose, parenchymatic and vessel cells than coniferous species. A factor of importance is the ratio between the tubular fibre wall thickness and lumen diameter. Expressed as a so-called Runkel-ratio (after Dr. R.O.H. Runkel), which is the ratio between twice the wall thickness and the lumen diameter (2W/L), the approximate limits of this ratio appear to be from 0.25 to 1.5 for species which produce pulp of reasonable quality.

Many of these, particularly the heavier species, have a high content of extractives. If hot water or alcohol-benzene extractives exceed 10 percent, it is very unlikely that the wood is suitable for pulp production.

There are samples of successful tropical plantations of hardwoods of both indigenous and exotic origin. A nine-year-old stand of Anthocephalus cadamba in the Philippines was calculated to yield annually the equivalent of 30 tons of oven dry wood per hectare. Certain species of Eucalyptus have produced very high yields in the tropics. While manmade forests of selected broadleaved species are not yet too common in tropical countries, they may be the best future source of wood raw material for pulp and paper in these regions.

It has often been suggested that, in order to overcome the complications created by the heterogeneity of the tropical broadleaved forest, they should be converted into plantations of selected species by:

1. clear-cutting existing stand;
2. collecting and processing logs suitable for lumber and plywood production;
3. collecting and processing logs suitable for pulping;
4. burning rest of wood;
5. replanting with selected species.

In view of lack of experience it is not possible to estimate the economics of these operations or to guarantee that the reforestation programme will be successful. If this is possible and economically sound, the pulp mill may have to accept 50 to 100 selected species of wood. Provided the volume distribution of these species is uniform throughout the forest, the mill should be able to produce pulp of uniform quality. Another solution may be to increase fellings and reduce pulpwood selection into a few well-recognized species or groups of species whose percentages in the mixture of wood pulped can be controlled and kept constant at the mill. Both the natural and artificially controlled homogeneously heterogeneous mixtures of wood have been pulped in laboratories or pilot plants, and the pulps produced have been of good quality. The prospects of utilizing mixed tropical broadleaved forests for pulp and paper production thus depend on technical, silvicultural and economic forestry aspects.

Though hardwoods cannot produce as wide a range of pulps and papers as softwoods, modern technology has narrowed this difference. Furthermore, for certain grades of paper, pulps from hardwoods are superior to pulps from softwoods.

To benefit to the highest possible degree from the economics of integration it is desirable to have available for the industrial plant both broadleaved and coniferous woods. This is an important point to keep in mind when harvesting or plantation plans are drawn up.

FIGURE 4. - Trial plots of exotic Pinus espinata and Araucaria angustifolia in Tanzania. Exotic plantation species require detailed pulping tests to determine their suitability.

Bamboos

Bamboos are used in substantial quantities in many tropical countries for pulp and paper production. Bamboo pulps can be classified as superior hardwood pulps and they have certain unique and desirable qualities for the production of fine papers. The main problems associated with bamboo as pulping raw material are flowering, harvesting and transportation costs. Indigenous bamboo stands flower every 30 to 40 years and die out after that. Plantations from seeds can be established to secure a continuous supply of bamboo, but the costs for plantation-grown bamboo are high. Because of its bulkiness and often scattered small stands, costs of cutting, collection and transportation can become prohibitive.

Conclusions

The purpose of the foregoing review is to form a basis for outlining a method and the steps to be taken to establish what prospects there are for tropical countries to use their wood resources for pulp and paper production. Because of the multitude of fields of knowledge and experience needed to cover forestry, technology, marketing, economics, etc., no single individual or group of individuals in the same profession can carry out the whole task and produce a useful answer. The following lists the steps expected to be feasible to be carried out by the forestry sector as the minimum required for the first stage of such an investigation.


Softwoods

Hardwoods

Bamboo

INDIGENOUS FORESTS




A. Preliminary cruising or appraisal of wood resources recording species by volumes and size

Yes

Yes

Yes

B. Determination of wood species which may be used for pulp and paper by:




1 - checking past experience from commercial operations and results from research work done

Yes

Yes

Yes

2 - determining moisture and bark contents and densities for all species

Yes

No

:No

3 - determining moisture and bark contents and densities for species whose specific gravity appears to be between 0.3 and 0.8

No

Yes

No

C. Determination of species and volumes which may be used by mechanical wood working industries

Yes

Yes

No

D. Preliminary selection of possible plant sites considering particularly availability of water and transport facilities and costs

Yes

Yes

Yes

E. Establishment of a preliminary management, logging and transport plan and, if applicable, a plantation plan for removing or growing species of industrial value in gradually increasing volumes up to a point where the resource is fully used or where costs would obviously become too high

Yes

Yes

Yes

F. Preliminary capital cost and operating cost estimates for E resulting in wood costs per bone-dry ton under bark delivered to sites selected in D

Yes

Yes

Yes

PLANTATIONS




G. Evaluation of afforestation and reforestation prospects for species which are known, or are expected, to have industrial value and selection at the same time of plant sites which appear feasible, considering in particular the availability of water and transport facilities and costs

Yes

Yes

Yes

H. Establishment of a preliminary plantation, management, logging and transportation plan based on minimizing the cost of wood harvested during the initial years

Yes

Yes

Yes

I. Preliminary capital cost and operating cost estimates for H resulting in wood costs per bone-dry ton under bark delivered to sites selected in G.

Yes

Yes

Yes

Once the foregoing information has been collected by the forestry sector, other professions can carry out concurrently with more detailed forestry work the following steps of the investigation:

1. marketing studies;
2. selection of types, sizes and locations of developments which appear technically and economically sound;
3. laboratory investigations;
4. technical and economic feasibility studies leading into a report which, in case of favourable results, will form the basis for financing the development.

FIGURE 5. - Swaziland. This view of the Usutu Pulp Company mill site gives an impression of the scale of operations and the mill's vicinity to the planted forest that furnishes the raw material, in this case Pinus patula. Variations in the pulping qualities of pines grown in exotic plantations in the tropics need to be carefully evaluated before mill projects are contemplated.


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