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Executive Summary
The UK Forest Resource


Secondary Metabolites From Trees
Non-Timber Markets For Trees
Extraction Technologies For Tree Metabolites
Adding Value To Tree Metabolites
Further Research
Modelling Tools
The UK Forest Resource
There are 2.7 million hectares of woodland in Great Britain, 30% of which is managed by the Forestry Commission. The remaining forest is privately owned by landowners and other organisations. The greatest proportion of Forestry Commission woodland is located in Scotland (60%) with 26% in England and 14% in Wales.
Conifer species account for 1.6 million hectares (59%) and broadleaved species 1.1 million hectares (41%). Only 11% of Forestry Commission holdings contain broadleaved woodland. Table 1 provides details of the main woodland tree species in Great Britain. The UK area is dominated by Sitka spruce, mainly due to the abundance of this species in Scottish plantations. Scots pine, lodgepole pine and larch species make up the bulk of the remaining woodland area. In England, Sitka spruce and Scots pine predominate, while in Wales Sitka spruce and larch species are the most common species. Most of the UK woodland area is contained in large block plantations, 64% of British woodland occurs in blocks greater than 500ha and 20% in woods ranging in size from 10 to 100 ha.
Over recent decades there has been a gradual increase in the area covered by British woodland, with the majority of new plantings being carried out by private landowners (Figure 1) who are supported by a range of options under the Woodland Grant Scheme.
The total volume (standing biomass) of wood produced in Great Britain has also been increasing over the past decade at a relatively stable rate. Predictions of future production, based on assessment of plantings and age of current stands, are illustrated in Figure 3, which shows a relatively constant increase over the next twenty years. Longer-term predictions indicate that by 2040, supply will fall back to current levels of production. Current annual production of wood from UK conifers is in the region of 10 million cubic metres (overbark standing). Production of wood from broadleaved species is expected to increase, but outputs remain small in comparison to those of softwood species. Commercial exploitation of the hardwoods is also hampered by the difficulties private owners have in finding reliable, competent harvesting contractors and markets.
Figure 1. New plantings in Great Britain over the past decade (FC = Forestry Commission)
(Source: Forestry Commission 2003)
Table 1: Area of woodland by main tree species (000's of hectares)
(Source: National Inventory of Woodland Trees)
Species GB England Scotland Wales
Scots Pine 227 82 140 5
Corsican Pine 47 41 2 3
Lodgepole Pine 135 7 122 6
Sitka Spruce 692 80 528 84
Norway Spruce 79 32 35 11
European Larch 23 14 9 1
Japanese/Hybrid Larch 111 33 56 22
Douglas Fir 45 24 10 11
Other Conifer 30 19 5 6
Mixed Conifer 18 9 8 0
Total Conifers 1406 340 916 149
Oak 223 159 21 43
Beech 83 64 10 9
Sycamore 67 49 11 7
Ash 129 105 5 19
Birch 160 70 78 13
Poplar 12 11 0 1
Sweet Chestnut 12 12 0 1
Elm 5 4 1 0
Other Broadleaves 120 84 18 18
Mixed Broadleaves 160 91 62 8
Total Broadleaves 971 648 206 118
Total - All Species 2377 988 1123 266
Felled 47 15 23 9
Coppice 24 22 1 0
Open Space1 217 72 134 11
Total Woodland 2665 1097 1281 287
1Areas of integral open space, each less than 1ha
Figure 2. Restocking in Great Britain over the past decade (FC = Forestry Commission)
(Source: Forestry Commission 2003)
Figure 3. Annual wood production (standing biomass) historic and forward predictions (thousands of cubic metres overbark standing)
(Source: Forestry Commission 2003)
Figure 4. Current age profile of woodland in Great Britain.
(Source: Forestry Commission 2003)
Price fluctuations in the wood supply industry are a significant problem for the sector. Trees planted during the boom of the 1970's and 1980's will come to maturity in the next decade, but prices for timber have recently slumped (Figures 4 & 5), and the decline in standing timber prices appears to be accelerating. Standing timber values dropped by 4% in the year to 2001 and 9.5% in the year to 2002. Clearly, increasing supply at a time of low prices is likely to exacerbate the problem.
Figure 5. Coniferous standing sales prices for Great Britain (£ per cubic metre overbark), based on Forestry Commission sales
The market for timber and timber products is very difficult with pressure from imports and the current strong sterling exacerbating the problem. Imports of softwood from Sweden and to a lesser extent the Baltic States and Ireland are exerting a negative effect on the profitability of the entire UK wood supply chain. The UK is currently only capable of supplying around 15% of its timber requirements, but, even in situations where there is demand, timber prices remain low.
Sources of wood for industrial use
Currently around 7.5 million tonnes (green tonnes) of UK produced wood is delivered to its wood processing industries, with hardwood species representing around 9% of the total. 56% of UK wood is delivered to sawmills, 22% to wood panel mills, 12% to the four UK pulp mills and the remaining 10% to other miscellaneous outlets (fuel, poles, fencing). These figures include around 0.2 million green tonnes of hardwood that is delivered to both saw mills and pulp mills.
There are 315 sawmills in the UK, but there are only 28 that can be classed as 'large' producers (producing more than 25,000m3 Pof timber). Based on Forestry Commission statistics, only around 54-58% of the green wood delivered to sawmills is converted to saleable timber, leaving significant volumes of timber co-product. The majority of this is used in the pulp and board industry. Around 0.3 million green tonnes of sawmill softwood co-products are used by the pulp and paper industry (in addition to UK roundwood deliveries of 0.8 million tonnes) and a further 3 million green tonnes are used in the production of wood-based panels (plus 20,000 green tonnes of hardwood). Very little wood is now imported by UK pulp and paper mills and imports of softwood for wood panelling has recently ceased.
Clearly there is already an established market for products derived from saw dust and wood chips. Any new products would therefore either have to compete with wood board and panels for this source material or utilise other process residues (e.g. bark). The other alternative means of increasing the market value of trees is by adding value to the by-products of pulp processing. The opportunities for these by-products are described in later sections. Other sources of wood include branches and lops and tops derived from forest management. Such resources are more widely scattered and require significant efforts to collect and transport, so high value outlets are required to justify the costs of their collection.
Exploiting added value
The competitiveness of UK forestry in relation to producers both in Europe and worldwide can be greatly improved by expanding the material utilisation of other wood constituents. In developing markets for tree products, a number of forestry-related issues have arisen that will need to be addressed to determine whether any new venture is commercially viable.
Composition and isolation possibilities will be dependent on the species used. Even within species genetic and environmental factors (e.g. climate, geology, season) will impact on the metabolite composition and hence the quantity and quality of the tree product. References reveal an abundance of chemicals and associated properties, however, there is a dearth of information on the potential yields and yield variability. This is particular problem for those tree tissues that are normally discarded such as leaves, roots and bark.
Metabolite yield is also affected by the time delay between harvest and processing, an important factor if the tree species is sparsely distributed (e.g. many broad leaved species), and the methods used to prepare the trees prior to processing. For example, pilot studies at the Oregon State University showed that good quality waxes could be extracted from fresh, mature logs of Douglas fir. This wax was competitive in performance to the commercial alternatives. However, waxes produced from mill-run bark were heavily contaminated with resinous extractives from the wood. The additional processing required to 'clean-up' the wax ensured that the product was never commercialised (Hergert, 1989)
There are clearly a number of interacting factors that will influence the success of adding value to wood products. A wide range of interests including foresters, researchers, extraction chemists, industrial processing chemists and business economists need to be involved in R&D programmes on tree husbandry in order to take the sector forward.
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Forestry Commission (2003).
Hergert,H.L. (1989) Lignans. Natural products of woody plants. (ed Rowe,J.W.), pp. 349-511. Springer-Verlag, Berlin