A Concept of Wood Use

The Forest Resource
Wood is the most frequently used building material in the world. It constitutes a renewable natural resource, when managed for sustainability. It is an important factor in the quality of our environment, from the air that we breath (Figure 1), a habitat for our wildlife and insects, flora, fauna and lesser plants, a source of natural medicines, to climate and land stability.

Because of over exploitation, both in the northern and southern hemispheres of the natural forests, it has become necessary to develop man-made or plantation forests, as distinct from natural regeneration. In recent years in the United States, over four million tree seedlings have been planted every day! Due to the long rotation period necessary for growing broadleaf trees, up to 150 years in the case of oak, there has been a shift in emphasis to increased softwood plantations. This is especially so in Ireland , which has the lowest forest cover in the E.U. at 8-9%.

It should be understood that while Ireland at one time was covered in natural forest, with oak as the dominant species, by the turn of this century forest cover was down to under 1% of the land mass. The government, in it's strategic plan for forestry, "Growing for the Future", has set a target of 17% land cover and planting of broadleaves will constitute 20% of all planting. The planting target proposed is 25,000 Ha per annum.
To meet the dual demands of supply and sustainability, coupled with over production in other agricultural produce, the E.U. is promoting a policy of change in land use in agriculture towards forestry by means of grant incentives. Farmers are being encouraged to plant this "new crop". In Ireland up until recently, forest ownership has been principally public ( that is state owned) which is the opposite of the case in the rest of Europe where forests are mainly privately owned. The new emphasis on farmer planting in Ireland is now redressing this imbalance.

Wood Quality
To meet increasing demand, there is now a greater level of managed or plantation forestry. Here the main objective of the forester/grower is usually to accelerate growth through other considerations that impinge on wood quality have to be accommodated. Quality is difficult to define precisely, for example; one definition would be as a measure of the characteristics of wood that influence properties of end products.
Laminated Timber Beams

The characteristics required for one product can often be quite different from those required for another. Quality may also be measured in terms of wood density, uniformity of growth rings, percentage of Knot-free wood, proportion of late wood or cellulose yield. Wood quality can be more correctly described as a concept.

While the concept of wood quality may be difficult to pinpoint, it can be said that several factors will influence the suitability of for a variety of end uses. These factors include, density, fibre length, uniformity of growth rings, percentage of knot free stem or bole, Straightness of grain, proportion of heartwood and presence of juvenile or reaction woods. The latter factors refer to the first 15 - 18 years of tree growth (figure 2) that produces wood of less stable properties than mature wood. Reaction wood is produced in response to environmental factors such as wind forcing a tree to bend or heavy branching on one side.

The forester/grower could be described as a production resource manager who is constantly seeking ways of improving the efficiency of the crop. The first choice to be made is the species to be grown and the source of seed which will give a high performance on a particular site. How the crop is grown will affect the end result or out-turn, but to enhance productivity, he will try to improve either the yield (volume of growth per annum) or the quality (hopefully both) of the timber being grown. Figure 3 shows the forester's options and their affect on growth:

Wood Us
We have referred to the demand for wood and sustainability of our forests and so should have a concept of global wood use.

Consider the following:
· A 25mm cube of wood contains approximately 5 million wood fibres, each 3.5mm long.
· If these fibres were laid end to end, the total distance spanned would be 17.5 Km ( over 10 miles)
· In the cube here would be approximately 2 million late-wood fibres and 3 million early-wood fibres.
· The 3 million early-wood fibres (Figure 4) would have about 300 million bordered pits and 1 billion ray-cross-field pits (Figures 5 & 6).
· Pulping the cube for paper would yield 4 grammes of pulp, enough to make shopping bag paper about ½ A4 size.
· If the cube were mechanically defibrated, the yield would be about 8 grammes of pulp, enough to make 20 squares of double-ply toilet tissue.
· The global average use of wood per person per day is 100 cubes like the one described, or 1.8 Litres (~ 0.9Kg) of wood.
· In the developed countries, about 80% of the wood is used for industrial purposes and 20% for fuel-wood.
· In developing countries, only 25% is used industrially and the rest as fuel-wood.
· World demand for industrial wood is more than 1.5 billion cubic metres and is increasing at a rate of 1 - 2% per year.
· 70% of the world's wood used for industrial purposes is coniferous (softwood) and 90% of the world's coniferous forest is located in the northern temperate zones.
· There is no Boreal forest equivalent in the southern hemisphere. The Boreal region includes always all 0f North and Central America in which the mean temperature does not exceed 18 Degrees Celsius.
· About one half of the world's natural forests are in the tropical or semi-tropical regions, but they supply less than 10% of the world demand for industrial wood.

The Wood Industry
Forestry worldwide sustains a broad industry base. This includes pulp and fibre (paper and board manufacturing - chipboard, fibreboard (MDF), Oriented strand board (OSB)), plywood and veneers, construction timber, furniture and joinery, pallet wood and fencing, crafts, agricultural mulch (bark), sawdust for agricultural and for fuelling kilns to dry the wood.

Irish forest sector industries are expanding rapidly. While some of this expansion is due to the use of new and emerging technologies, it is to a large extent due to the arrival on-stream of increased timber supplies from our own forests. This development in turn is creating a demand for a skilled workforce including graduates who can spearhead the optimum economic utilisation of the forest resource in a manner that is socially and environmentally appropriate. The Bachelor of Technology Degree in Wood Science and Technology, at the University of Limerick, is currently educating and training graduates to meet the needs of this dynamically developing industrial sector.

Wood is a natural, renewable material and has a flexibility in use as no other material possesses. It's conversion and processing is a low energy user and the range of potential products is constantly expanding with new technologies. We are fortunate to have such a wonderful resource and must continue to manage it wisely through sustainable forest management.


References:
Brazier, J. D. T., Lavers, G.M. and White, N. C (1976), An evaluation of Home-Grown Sitca Spruce, P.R.L., B.R.E., Garstown Watford.

Desch, H.E., (1991), (Revised Dinwoodie, J. M.), Timber, Its Structure Properties and Utilisation, (6th ed), Macmillan Press Ltd., London.

Doyle, F., (1999), Wildlife Photograph, Crann Calander.

Forest Service (1996), Growing For the Future, (A Strategy Document), Department of Agriculture, Food and Forestry.

Haygreen, J. G., and Boyer, J. L., (1982), Forest Products and Wood Science, Iowa State University Press, Ames, Ireva, USA.

Jozsa, L. A.,(1994), Owners Manual for a 2.5cm Softwood Cube, Forintek Canada Corporation.

http://www.forest.gov.my/ewup.html

http://www.commsun.its.csiro.au/research/mdb/woodutil.html