STANLEY A. CLARKE
Chief, Division of Forest Products, C.S.I.R.O., Australia.
COMPLETE utilization of tropical forests has long been the hope of the forester. Occasionally it is realized in more or less pure stands or in areas with a comparatively few species of which all are of value. More often forests are very mixed and a few preferred species only are exploited. Sometimes where pure stands do occur they are intermingled with areas of mixed species.
Under such conditions of incomplete logging, the logger has to work over a large area to secure the required yield of logs and because extraction lines, roads, etc, are largely affected by area, then cost per unit of timber secured is greatly inflated. In addition, some of the most economical logging equipment is only feasible where extractable volume per acre is high, that is, in reasonably dense stands which are more or less fully logged. The forester is also faced with a problem in mixed forest, of what to do with the remaining trees which may comprise 50 percent or more of the stand and may interfere with regeneration and growth of the preferred species.
Any means of using non-preferred species can therefore be of importance in giving:
(a) an all-round reduction in logging costs;
(b) an increase of timber supplies:
(c) assistance to the forester in growing the next crop.
These non-preferred species may be regarded as inferior simply because they are unknown or because any one species is in too limited a quantity to justify market promotion: they may be susceptible to troubles in the log such as pinhole borer attack and fungal staining, to troubles during sawing from high silica content or tension wood, or to troubles after sawing such as powder post beetle attack. They can vary in density from very low to very high, in color from almost white to almost black and in texture from loose fibrous material to strong close-textured wood.
Practically all these woods can produce one or more of the sheet materials - - insulation board, hardboard or particle board - although naturally for any use there will be selected species or groups of species which will give the best results because of density, ease of disintegration, color or some other desirable attribute.
In selecting the type of product and the woods most suitable for it, market conditions must first be explored. Following this, there are then a number of general principles which can be applied, although naturally there can be exceptions to these principles because of special or outstanding circumstances. Light weight and light color can be useful attributes for wood for insulation board. Very brittle woods should be viewed with suspicion because of possible difficulty from excessive fines in pulping. Heavier timbers can be used but may involve a cooking or presteaming treatment. Similarly, dark color can be overcome by coating on the forming machine or by prime coating with paint, but all these add to cost.
Almost any wood can be used for hardboard, which is the least exacting of all boards as far as raw materials are concerned. Any selection would be on obvious lines such as selecting species most easily handled and avoiding if possible those with high extractive content.
For particle board, the light and medium density timbers are most desired. Susceptibility to borer attack (lyctus) is probably not a factor with particle hoard especially where the particles are small. In any case, in tropical areas antifungal and antitermite provision is usually essential and this can eliminate borer attack.
Apart from characteristics of raw materials, there are other factors to be taken into account such as local traditions of use of similar materials, climatic conditions and problems of water supply and effluent. Difficulties with the last named might influence selection towards dry felting rather than wet felting processes.
If insulation board, hardboard and particle board have not been in use to any extent in the particular country concerned there would be great advantage in importing quantities and trying these out under local conditions. Special problems which cannot otherwise be foreseen can unexpectedly arise and can result in a new plant getting off to a very poor start. In one case, a new insulation board suffered from a strong prejudice because it was very susceptible to damage by rats and mice prevalent in the area. The need for special antifungal treatment and antitermite treatment, as well as the desirable moisture content to which the board should be humidified are some of the factors which might be disclosed.
There is a tendency today to set up a laboratory when an industry new to a country is first proposed. In the case of building boards from wood, such a proposal is fraught with difficulties and only in exceptional cases is to be recommended. In the first place, it is not feasible to set up laboratory plant to test out all processes, because some of these require vastly different, equipment. Secondly, such experimental equipment can usually only be provided with laboratory size units which do not always detect the problems likely to be encountered. Thirdly, the most likely types of plant required can be selected from information already available and, once types are fixed. manufacturers of plant have facilities for carrying out experimental work with new materials using staff of long experience and often full-scale equipment. Such manufacturers are then in a position to incorporate in the design of the plant to be supplied, any special features indicated by the results of the experiments.
In the countries where manufacture of fibreboard and particle board is most advanced, it is customary to look for the raw material for these products in the forest and milling residues which are mostly in the form of small or malformed trees, sawmill edgings, dockings, etc. The position is very different in the mixed tropical forests because the non-preferred trees are often of good size and form. It is, therefore, as well to remember that there is another sheet material, plywood which can be made readily from the logs available. Plywood has the advantage that it can be produced in small plants requiring no great skill, operating day time only if desired and producing a range of products from the thinnest three-ply to plyboard of the usual thicknesses of particle board. Attractive figures can often be obtained from many tropical woods either by ordinary rotary cutting or by sawing the log in half and dogging it so that it swings on an axis near the outer sapwood. This range of products and the small capacity can be of great importance in underdeveloped countries where transport is often a problem particularly at certain seasons of the year.
Modern development in log sanitation from stump to plant and in simple and cheap dip-diffusion treatments of veneer to prevent borer, termite and decay attack have revolutionized the future of the once unwanted species. For example, in a part of Borneo before the war, the major expenditure in forest stand improvement was for poisoning ramin (Gonystylus spp.) so that other species could be encouraged. Today, ramin is the major export species, and logs are shipped to Australia and elsewhere, peeled, treated and made into plywood which is well-esteemed. Forest practices have been worked out to reduce pinhole borer attack and staining to negligible proportions and the treated veneer is absolutely immune to powder post beetle attack.
It would be idle to assume that in all these sheet materials there is the solution to the problem of the complete exploitation of tropical forests. The controlling factor must be the markets available and, until they are greatly expanded, the contribution which boards can make towards overall tropical forest utilization will be small. However, there will be many places where an active and growing demand can be built up and here the logger and the forester will have an added incentive towards fuller utilization of mixed tropical forests.
An important feature of the consultation on insulation board, hardboard and particle board held this year in Geneva and sponsored by FAO and ECE was the organization of an exhibition to show the latest developments of these industries. Over 1,000 specimens of boards and raw materials were contributed by commercial concerns and technical institute and the display included eight small-scale models of plant, and a large number of photographs and charts, to illustrate different types of equipment and processes of manufacture.