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Executive Summary
Introduction
Methodology
The UK Forest Resource
Secondary Metabolites From Trees
Non-Timber Markets For Trees

Cellulose
Lignin
Hemicellulose
Xylitol
Resins, Waxes and Oils
Rosin
Fatty Acids
Tannins
Gums from Larch Species
Non-tannin uses for Wood Bark
Overview of Opportunities in key Industrial Sectors
Market Issues
References

Extraction Technologies For Tree Metabolites
Adding Value To Tree Metabolites
Further Research
Modelling Tools
Non-Timber Markets For Trees
Wood is a very versatile material that can be used in a wide variety of non-timber applications by exploiting its structural component tissues and the oil and resinous metabolites contained in the timber, roots, bark and leaves. Wood typically comprises of 40-50% cellulose, 25-30% hemicellulose, 20-30% lignin and 2-5% resins and oils. Each of these components is currently, or has the potential to be, commercially exploited. However, a key factor limiting the widespread exploitation of this natural and sustainable resource has been competition from oil and coal derived feedstocks.
The most commercialised non-timber use for trees is as a cellulose feedstock for paper production. However, some innovative companies are taking the lead in developing alternative uses (Harms 1998): for example, Lenzing, an Austrian company, extract cellulose fibres for industrial processes from around 95% of its country's harvested beech trees . This utilises around 40% of the tree biomass and accounts for around 15% of the country's 1.3 million tonnes of cellulosic products (Harms 1998). Lenzing has also sought to add value to the feedstock by utilising a further 10% of the harvested biomass as a source of fine chemicals. The biomass that remains after processing is used to produce energy thereby reducing fossil fuel demand and carbon emissions. With an EU-wide imposition of carbon taxes and credit schemes, industry can now market and brand materials that address environmental issues.
There may also be opportunities for utilising process residues. Forest trimmings (e.g. leaves and branches) account for 15% of the harvested biomass and 40% of felled timber is sawmill co-product (e.g. wood chips, saw dust and bark). Consequently only 25% of felled softwoods, such as spruce, and 50% of hardwoods become structural timber (Harms 1998). These pocess residues material are being exploited by the U.S. National Renewable Energy Laboratory, which is developing adhesives from phenolic compounds derived from saw dust and bark; this is expected to reduce the cost of production of wood adhesives by 25% (NREL 2002). Also, Folionics have commercialised plant growth regulators from pine needles (Robert Webb, Clark MacTavish pers com.). Such innovations together with further R&D have the potential to add value to trees at a time when the value of natural resource timber has fallen to a 25-year low (Forestry Commission 2001).
The following section provides a review of current and emerging non-timber products and associated markets for tree metabolites.
Industrial Use of Major Metabolites
The most important non-timber use of wood today is the production of pulp to make paper. Pulps are produced either through thermo-mechanical or by chemical action. In chemical pulping, all constituents except cellulose are dissolved using sulphite or sulphate (Kraft) processes (further details are available in the extraction section of this report)
Cellulose
Paper industry
More than 95% of the annual global cellulose output (130 million tonnes) is used in the production of paper and demand is increasing. World paper production increased from 193 million tonnes to 323 million tonnes between 1985 and 2000. Total paper production in countries represented by the Confederation of European Paper Industries (CEPI1) amounted to over 90 million tonnes in 2000 (CEPI 2003). Wood pulp production, for paper making, in CEPI countries amounted to 38 million tonnes in 2000, while consumption stood at 43 million tonnes.
The UK currently produces only 27% of its total demand for pulp and is a relatively small player in the European market (Figure 6). UK paper production by market sector is illustrated in Figure 2. The UK pulp industry utilises home-grown softwood for newsprint and packaging boards, but production is concentrated at a few high-volume manufacturing sites. These sites all pulp using a thermo-mechanical process, which can make use of sawmill co-product and small roundwood. The financial performance of saw and pulp mills is closely interlinked through trade in these co-products.
Figure 6. Total Pulp Production in CEPI Countries (Thousand tonnes)
Pulp is processed into paper with thermo-mechanical techniques, as these minimise damage to the cellulose fibres. During chemical processing, the pulp is dissolved and converted by sulphite or Kraft process reactions to produce a range of cellulosic end products. The sulphate (Kraft) process is responsible for around 80% and the sulphite process around 7% of cellulose production (the balance being made up by mechanical pulping). Chemical pulp plants have been established in the UK in the past (e.g. Fort William). High outputs are required (80,000 tonnes of pulp per annum) to ensure economic viability, which requires significant investment to transport supplies of raw material (Knags 1977).
Figure 7. UK production of paper (million tonnes) by market sector
A wide variety of materials are derived from dissolved pulp and these have a wide range of markets including:
Pure cellulosic products, created by manufacturing an intermediate dissolved derivative or direct dissolution (e.g. Viscose and Lyocell).
Derivatives of cellulose - resulting from intermediate stages of cellulose processing (e.g. cellulose acetate, carboxymethyl cellulose)
It is estimated that 3.8 million tonnes of products manufactured from pulp in 1998 contained components derived from chemical processing (Harms 1998) (Table 4). This represents around 3% of total pulp output. However, industrial use of such pulps is constrained by the relatively low-cost of alternatives, such as petrochemically-derived synthetic polymers.
Viscose fibres account for the major alternative use for dissolved pulp, with around 2 million tonnes of fibre produced per annum. Cellulose acetate is an industrially-important ester of cellulose and is used in a wide range of products including cigarette filters, films and other coating materials. It is also used in moulded articles (e.g. spectacle frames), as a micro- and ultra-micro filtration membrane in the pharmaceuticals sector and as a matrix for administering slow-release steroid drugs.
Lyocell fibres are produced from Eucalyptus and pine pulp. Both Viscose and Lyocell fibres are being marketed as environmentally-friendly alternatives to cotton and synthetic fibre production by Lenzing AG in Europe.
Cellulose ethers are a wide-ranging family of cellulose derivatives, commonly used in the food and pharmaceutical industry. Methyl, ethyl and propyl cellulose esters are used as drilling aids in mining and as detergents. They are also used as coatings and adhesives in cosmetic, pharmaceutical and food products.
Table 4. Key areas of application for chemically-dissolved pulp (%)
% by Sector
Viscose  
1. Staple Fibres 44.7
2. Filaments 7.8
3. Tyre Cord 1.4
4. Cellophane 4.6
Lyocell 1.0
Cellulose Acetate  
1. Cigarette Filters 16.0
2. Textile Filaments 6.2
3. Solid Materials 0.7
Cellulose Ether  
1. Carboxymethyl-cellulose 3.2
2. Non-ionising Ether 8.2
Cellulose Nitrate 4.9
Microcrystalline Cellulose 2.0
Source: (Harms 1998)
Other Materials
The spent liquors arising from processing wood pulp mostly contain lignin, polysaccharide derivatives and various resins and oils. The composition and ease of isolation of these materials depend on the processing method and wood species used.
Lignin
Following sulphite or Kraft processing, the 'spent' liquor that is left after the removal of the cellulose fraction is a rich source of lignins (Table 5 and 6). Lignin is used as an intermediate product in many industries, although detailed information on the quantities utilised have not been reported.
Table 5. Composition of sulphate black liquor (% of dry weight)
Softwood Hardwood
Kraft Lignin (KL) 45 38
Hydroxycarboxylic Acids 22 24
Acetic and Formic Acid 10 20
Resins, Fatty Acids 7 6
Turpentine 1 -
Others (Including Ashes) 15 12
Source: (Harms 1998)
Table 6. Composition of spent sulphite liquor (% of dry weight)
Softwood Hardwood
Lignosulphonate (LS) 55 43
Hexoses 14 5
Pentoses 6 20
Non-cell. Carbohydrates 8 11
Acetic Acid 4 9
Resins and Extracts 2 1
Ashes 10 10
Source: (Harms 1998)
The Kraft process yields unsulphonated Kraft lignins (KLs) that are used, for example, in the production of vanillin and dimethyl sulphoxide (DMSO)). These Kraft lignins have a current market value of 0.1 to 0.5 € per kg (£0.07 to £0.27/kg) and around 1.4 million tonnes of lignins are produced per annum. These materials are used in the polymer resin industry to manufacture plywood and their derivatives (e.g. alkolyzed lignins) are a potential feedstock for the polyurethane industries.
Sulphite lignin (LSs) is predominately used as a stabiliser in drilling muds and emulsions. However it has a wide range of other potential applications including dispersants in paints, clay, porcelain, dyes, pesticides and industrial cleaning agents. It is also used as a binder and filler in the pelletisation of animal feed, as a substitute for carbon black in tyres and as an additive to concrete and gypsum.
Hemicellulose
Hemicelluloses are extracted during the sulphite pulping process (in the Kraft process hemicellulose is degraded to organic acids) and can be used as a fermentation feedstock for the production of ethanol and other alcohols (e.g. butanol, arabitol, glycol and xylitol), organic acids (e.g. acetic acid), acetone and gases (e.g. methane and hydrogen). Individual sugars can be derived from hemicellulose and xylitol, derived from xylose, has been developed as a low-calorie sweetener. Pentoses contained in hemicellulose can be used to produce furfural as a solvent for resins and waxes, and as a starting material for aromatic substances, preservatives, disinfectants and herbicides. Furfural is also converted to furfuryl alcohol and thence to furan resins that are used to manufacture binders for foundry resins. In Austria, processes have been developed to extract furfural from the spent liquor left from the chemical pulping of beech (Harms 1998).
Xylitol
The production and use of non-calorific sweeteners represent a rapidly growing worldwide market and tree metabolites are potential candidates for this application (e.g. hydrochalcones and diterpene glucosides). A market for the tree derivative, xylitol has already been developed. Much of the supply is currently derived from Finnish birch, but it can be derived from any hemicellulose source. Current demand for xylitol is estimated at £100 million (Business Communications Co.) and is predicted to grow at a rate of 4.2% per annum in the short term. Current price range from £2.44 - £3 per kg. Price is subject to fluctuation and it has been in decline in recent years due to increased competition. Production is currently limited to thee main producers.
Resins, Waxes and Oils - 'Naval Stores'
Resins, waxes and oils can be extracted from living trees by 'tapping', or from the bark and wood during pulping. The most important by-products of wood pulping are production of turpentine and tall oil. Tall oil is used to produce a variety of resins and these products are often referred to as 'Naval Products', which derives from their traditional use in shipbuilding.
Most of these materials originate from conifer oleoresins (compounds which consist of an essential oil and a resin component). Oleoresins are the source of turpentine (an essential oil), rosin (a resin) and natural rosin derivatives that include tars, pitches and oils. Wood naval stores can be extracted by dissolving resinous wood chips; however this is not currently favoured due to solvent losses and high energy costs. Consequently, most naval stores are derived from the Kraft pulp process, where pine chips are heated in an alkaline solution and the resulting gasses vented and condensed to yield sulphate turpentine. This yields around 3-6 litres per tonne of cellulosic pulp.
The post-pulp spent-waste crude tall oil (CTO) (referred to as spent or black liquors above) is a potential source of fatty acids and rosin. Tall oil is fractionally distilled to produce high quality by-products. Around 30-100 kg of tall oil, which contains 40-55% rosin, is produced per tonne of cellulosic pulp, depending on species.
Oleoresin products in pine needles
A limited quantity of perfumery-grade pine needle oil can be extracted from Pinus species, but these too closely resemble turpentines to command the premiums required to justify their extraction.
Turpentine/pine oil
Turpentine is used as a solvent in paints and varnishes. Its use depends on chemical composition and this is determined by both tree species and method of extraction. Turpentine can be fractionated into its component parts (unsaturated bicyclic monoterpene hydrocarbons, smaller amounts of monocyclic monoterpenes, alcohols and some sesquiterpines and diterpines), but this is only economically viable on a large scale. The monoterpene hydrocarbons (primarily a-pinene) are used to prepare synthetic pine oil (the biggest single turpentine derivative), polyterpine resins, perfumes/fragrances and insecticides. Variation in extraction method, fractionation and blending produces oils with different properties. In the US, 90% of pine oil is used in cleaning and disinfectant formulations and around 330 thousand tonnes of turpentine are produced per annum from wood sources. There is a growing demand for terpene solvents in the United States across a range of sectors (Table 7 and 8)
Table 7. Green solvent demand in the United States - current and predicted demand for terpene solvents (tonnes)
2002 2007 2012
Pinenes 77600 104800 137900
D-Limonene 34500 49400 68000
Source: Freedonia Group
Table 8. Pinene solvents demand in the United States by market current and predicted demand (tonnes)
2002 2007 2012
Industrial uses      
Cleaning Products 46266 62142 82099
Printing Inks 4989 7257 9979
Adhesives and Sealants 4989 6804 9072
Other 17236 22226 28576
Source: Freedonia Group
Pine oil is
  • A good emulsifier
  • An excellent solvent
  • An effective germicide (of low non-target toxicity)
  • An effective 'frothing agent' for floating-off impurities
  • A penetrant and dispersing agent for use in textile fibre processing
Petroleum-based alternatives have taken most of turpentine's traditional markets, but small niche markets exist for artist and home use. However, there may be potential for renewed commercial interest in these solvents as replacements for the ozone-depleting chlorofluoro-carbons.
Polyterpene resins and adhesives
A range of low molecular-weight polymers can be produced from tree-derived monoterpenes and diterpines by cationic polymerisation. The characteristics of the polymer are influenced by the mix of polymer building blocks. These polymers are used to impart 'tack' in adhesive compounds. Polyterpene resins are used in the preparation of solvent-based pressure-sensitive adhesives and diterpene resins in the manufacture of hot-melt adhesives. Other applications for these tacky, thermoplastic properties include use in surface coatings and sealants.
Flavours and Fragrance
This area represents a small fraction of terpentine utilisation (10-15%). In most cases, the terpentine components are converted to other chemicals. Amongst this family of compounds, β-pinene is the most important feedstock. Menthol is produced from β-pinene and is used for its 'cooling' effect (the L-isomer in particular) in cigarettes, cosmetics and flavourings (esp. peppermint); a wide range of flavour and fragrance additives are derived from myrcene, produced by the pyrolysis of β-pinene.
β-Pinene derivatives include:-
  • Linalool and its esters -'lilac-like' fragrance;
  • Gerianiol, nerol & esters - 'rose-like' fragrance;
  • Citronellol - a precursor of rose oxide an important oil in perfumery;
  • Hydroxycitronellal - 'Lilly-Of-The-Valley' fragrance.
Citral - an intense lemon quality used in preparation of citrus flavours and fragrances.
Further chemical processing of Citral with acetone produces a mixture of ionones, of which the α-isomer is widely used for its violet odour. Condensation of citral with 2-butanone gives methylionones, which are also valued as perfume agents.
Other perfume ingredients can be derived from pyrolysis of a-pinene, such as tertiary alcohols with sweet floral odours that are used in soaps and cosmetics, and citrus-type colognes. Hydrogenation of α-pinene produces camphene, which can be used to synthesise materials with a sandalwood odour, a costly process otherwise.
Limonene (diterpine) is the starting material for synthesising carvone. Carvone has the flavour and odour of dill and has recently been developed as a sprout suppressant for use in potato stores. However, there are a number of other natural competitor feedstocks for this derivative, including caraway seed.
Insecticides/repellents
Pine oil derivatives, pine tar, isobornyl acetate and citronella are used as insect repellents. Pine oil boosts the activity (by synergy) of pyrethrum, a relatively expensive insecticide. However, it is difficult to compete with products derived from petrochemical sources and the costs of registration for new pesticide products can be prohibitive, unless fast-tracked under schemes like the US EPA's Generally Regarded as Safe (GRAS).
Rosin
Rosins are the non-volatile resin constituent of pine oleoresins and consist primarily of diterpine resin acids along with 5-20% 'neutrals'. These neutral compounds can affect commercialisation of rosins by interfering with further chemical processing. In most cases, rosins are chemically modified in the manufacture of value-added products. World production of rosin is estimated at 1.2 million tonnes per annum. Uses for rosins are subject to intense competitive pressure from synthetic compounds, and there is also competition between rosins derived from gum (i.e. tapped sources) and tall oils (pulp derived).
Paper sizing
Rosins can be used to waterproof paper and currently accounts for 30% of rosin production. However, improvements in paper production technologies mean that less rosin in now being used per tonne of paper.
Polymer manufacturing
Rosins are used as emulsifiers in production of some polymers (synthetic rubber and ABS (acrylonitrile-butadiene-styrene) and other speciality polymer products). They also add 'tack' to polymers.
Adhesives
Around 20% of the resins used in adhesives are derived from rosin. Key uses are in pressure sensitive solvent-based rubber cements, and mastics. The other key area is in hot-melt adhesives that are used in shoe manufacture, product assembly, carpet sealing tape, bonding paper (corrugated paperboards), book binding and laminates.
Inks
Rosin derivatives are used with other resins and polymers in components of ink formulations where they impart binding, film forming and solvent qualities to the final product. Modified rosins with high melting points can be used in printing inks.
Miscellaneous uses
Rosin esters impart gloss, levelling and flow characteristics that are used in emulsion floor polishes and shoe polish. Other applications include the coating and sealing of cans in food packaging and the controlled-release encapsulation of fertilisers.
Other rosin derivatives:
  • Alcohols - used in plastic heat stabilisers
  • Ethoxylated amines - used in corrosion prevention and speciality cleaning
  • Polyols - used in polyurethane foams
  • Amines - antimicrobials (fungi, bacterial and algae)
Fatty Acids
Fatty acids are used in the speciality oleochemicals market as intermediates or with more direct applications in surface coatings, printing inks, adhesives, corrosion inhibitors, gelling agents (soaps) and lubricants (esters). Palmitic acid can be derived from tall oil, as well as high quality oleic and linoleic acids. Polyglycol esters derived from tall oil have extensive use as emulsifiers and non-ionic surfactants.
Tannins
Tannins can be extracted from wood and are widely used in the food (beer/wine making), and leather industries. The only native plant-derived tannins used in the leather industry are oak bark tannins derived from hand-stripped bark (mechanical stripping causes an undesirable increase in red colouring) and demand is unsaturated in this particular sector. The total requirement is small in order to meet the demand from about 6 UK tanneries. The laborious method of collection means that tree-bark-derived tannins are uncompetitive compared with synthetic tannins and imported vegetable-based tannins. The world market for tannins is estimated at 500,000 tonnes per annum. Tannins are concentrated in bark: for example, oak wood contains 1% tannin by weight, while oak bark contains 12% tannin by weight (Aaron 1976). Tannin content varies widely between species, ranging from 6% (by dry weight) in birch bark up to 17% in Sitka Spruce (Aaron 1976). Table 4 illustrates the current EU supply/demand for tannin extracts and derivatives. The market volume is small, with the average price for UK Manufacturer Sales at 0.54 £/kg and the average price for UK net supply at 0.56 £/kg. Tannins have potential for use in particleboard adhesives (see later section on adhesives).
Table 9. EU Import/export balance of tannin extracts of vegetable origin, tannins and their salts, ethers, esters and other derivatives in 2002
Volume Traded (tonnes)
Total Exports from outside the EU 44.8
Total Imports from outside the EU 168.0
Net Balance 123.0
Source: (UK Government Statistics 2003)
Tannins have been studied as antifeedants for crop insect pests (e.g. Colorado Beetle), and tannins from oak have been used as molluscicides. However, very few commercial products have been developed because of the difficulty of obtaining consistent effects.
Gums from larch species
Larch arabinogalactan is a polysaccharide found in all larch species (5-35% of dry weight in heartwood). Its main use is as a replacement for gum arabic in food, cosmetic and pharmaceutical products. It is also used as a low-calorie bulking agent in admixture with artificial sweeteners and can also be used to make other low-calorie products. It also has some unusual properties in that it is reported that it can inhibit the setting of Portland cement.
The three main world exporters of gum arabic are the Sudan, Chad and Nigeria. Trade in gum arabic has risen by 25% over 1995-2000; in 2000 world trade of gum arabic was worth £54 million. The main importers are France (46%), USA (21%) and the UK (12%) (Agro-Ind, 2002). World market prices for gum arabic show considerable volatility. Prices were very low during the 1990s but have since recovered. Use of larch arabinogalactan is limited as its properties are very similar to those of gum Arabic, which is widely available.
Table 10. EU imports of gum arabic (tonnes)
Source 1995 1996 1997
Sudan 10,752 10,834 9,801
Chad 5,453 4,941 6,777
Nigeria 3,683 4,314 5,506
Non-tannin uses for wood bark
Up to 100 tonnes of bark per day can be produced at UK pulp mills and sawmills, and bark accounts for approximately one eighth of wood overbark volume, though this varies between species (from 9% in spruce up to 18% in Corsican pine and European larch). Wood bark is currently used in potting composts, mushroom growth media (with added chalk) and to help with water drainage and aeration (Aaron 1976) , although it holds less water than peat. Fresh bark can inhibit growth of some plant species. The presence of monoterpene esters in bark means that the material requires heating through appropriate composting prior to use.
Quercetin has been derived from dihydroquercetin found in Douglas fir bark. This metabolite has a wide range of pharmaceutical applications and is also used as an antioxidant additive for foods, extending their shelf life.
Bark is also used in a compressed form to produce building blocks that have superior heat and sound insulation properties over traditional cavity wall blocks. Approximately 2.2 tonnes of bark are required for a detached 3-bedroom dwelling (Aaron 1976). Bark can also be used to control oil spills, as it absorbs oil more readily than water, reaching the saturation point at 3.5 to 4.5 times its dry weight; its performance is thus better than chopped straw, with spruce being superior to pine bark in this application (Aaron, 1982).
Animal bedding
At present 250,000 tonnes per year of wood shavings are used for horse bedding in the UK and the potential market remains far from saturated: There are 900,000 horses in the UK, each horse potentially requiring 10-13 tonnes per year of wood shavings. The price of wood shavings varies from £100-£250/tonne according to quality. If the requirements for cattle are also included, the potential market is very large. Wood and bark chips have been used as deep litter for cattle and have the added advantage in that they absorb odours (see biofilters below). In poultry houses, good airflow is required when using wood derivatives to prevent the development of fungal moulds and associated respiratory problems.
Mulches
In recent years there has been an increase in the use of wood chips, wood mulch and bark for recreational purposes such as playgrounds, public gardens, motorway embankments and individual household gardens, as well as for paths and tracks etc. Much of this is derived from thinnings, harvesting residues or sawmill co-product. The development of modern chipping machines to recycle these residues and produce new products such as wood chips, has led to expansion of the sector and has enabled more recycling to be carried out. Although there has been growth in this sector, this is unlikely to continue indefinitely. The market is more likely to fluctuate than continue to grow. Currently, spruce and pine are utilised for this application. Coarsely pulverised wood and bark can also be used in paddocks and gallops.
Biofilters
A new potential market for wood chips is in the creation of biofilters. Biofilters are made of moist organic material and are used in a wide range of facilities including livestock housing. Air is forced through the biofilter, which physically removes dust and, through the action of bacteria living within and on the surface of the wood chips, adsorbs and oxidises offensive odours including ammonia. Work has been conducted using biofilters in many livestock housing situations. Biofiltration can reduce odours from livestock and poultry housing by as much as 95% and ammonia emissions by 65% (Nicolai & Schmidt 2002). Buildings with mechanical ventilation or pit fans can be most easily adapted. Filters have included use of mixes of compost and wood chip. In the case of peat moss and compost-based filters, odour reductions of 60-80% have been recorded (Toombs 1997). A successful mix for animal housing biofilters ranges from ratios of 50:50 up to 30:70 by weight of compost and wood chips or wood shreds. Wood provides porosity and structure while the compost component provides microbes, nutrients and reduces water loss.
Overview of opportunities in key industrial sectors
Adhesives
In 1999, the total adhesives market volume amounted to 1.7 million tonnes worth around £2.3 billion. The UK alone uses 0.2 million tonnes of adhesives per annum with a market value of £0.4 billion. Figure 8 illustrates the sales volumes for different sectors of the market. Natural polymers and hot melts represent significant portions of the adhesives market where tree-derived products could find a niche.
Research in the US National Renewable Energy Laboratory (NREL) has demonstrated the potential for development of plastics and adhesives from wood. Wood residues are used to produce phenol-like compounds derived through a controlled pyrolysis. This process yield a pyrolysis oil, which can be further refined. Phenol is a primary starting material for many adhesives. It is converted into phenolic resins (e.g. phenol formaldehyde), which are used in significant quantities to produce boards and plywood. The largest markets for phenolic resins are adhesives for plywood, fibrous and granulated wood products and laminates. According to the Phenol Producers Association, sales of phenol-formaldehyde resins account for half of the production of heat-set adhesives. Global production of these phenolic resins reached 2.9 million tonnes in 2001.
Figure 8. Breakdown of sales share for adhesive markets in Western Europe in 1999 (FEICA, 2000)
Tree-derived phenol has to compete with fossil fuel-derivatives. The Coalite plant in Chesterfield, which is the key production facility for phenol in the UK, produces 6,000 tonnes of phenol per annum according to the Phenol Producers Association, but this level of output is insignificant compared with the quantities produced in neighbouring European countries and the whole EU is a net exporter of phenol.
Recently, relatively high oil prices have led to increasing costs for synthetic resin adhesives at a time when the demand for bonded wood products is increasing. Costs of adhesives can account for up to 32% of manufacturing costs (Sellers, 2000). Research at the US National Renewable Energy Laboratory has demonstrated that it is possible to produce phenolic resins from wood for about half the cost of those produced from fossil fuels. It is calculated that this could reduce the cost of resin adhesives by around 25%. Lignin-modified phenol-formaldehyde resins have been widely used in the US to bond fibreboards and plywood, where the lignin component is used to replace up to 35% of the phenol in the resin adhesive. Work continues in the US to seek natural alternatives to synthetic resins as wood binders where up to 50% of the primary phenol binding agent has been replaced by wood-derived phenol components (Sellers, 2000). In addition, these phenolic compounds can also be used in Bakelite plastic in the production of moulded plastics and foam insulation. Phenolic resins for adhesives and plastics account for around 20% of phenol use in the US. It is estimated that they account for 30% of phenol production globally in a total market worth £2.5 billion. The world phenol market is subject to supply and demand fluctuations, which will influence costs and the competitiveness of tree-derived resins, but global demand for such resins is expected to increase, particularly in developing countries, central and Eastern Europe.
Tannin-based adhesives have been developed in Germany (Bakelite AG) to make marine grade oriented strand board. The tannins are extracted mainly from American, Asian, Australasian and tropical tree species, but also temperate pine species. The UK produces 56% of its home consumption of chipboard, strand board and medium density fibreboard (MDF) (Banks and Cooper, 1997).
Detergents and surfactants
In 2001, the detergents market for the EU15, Switzerland and Norway was worth in excess of £18 billion. Germany is the largest national market in Western Europe, followed by France, UK, Italy and Spain, which together account for 80% of the Western European market. Figure 9 illustrates the market share for different product categories. The total quantity of surfactants sold in Western Europe is about 2 million tonnes (CESIO data on CEFIC website). Materials derived from cellulose, lignins and terpentines have markets in sectors selling industrial products, household cleaners and domestic products.
Figure 9. Share of the detergent market by sector (sales volume) (Data source: AISE)
Market Issues
This review has shown the wealth of products that can be derived from trees and outlined the innovative processes that are being developed to extract them. To develop markets for such products, a number of issues will need to be addressed to ensure any new venture is commercially viable.
The scattered distribution of some species may make extraction expensive unless high-value markets can be developed. The UK Forestry Commission has also highlighted the imposition by local authorities of weight restrictions on the transport of raw materials from some areas until roads are improved. This could add significantly to costs of production. Investment costs for new developments and production facilities could be minimised by co-locating extractive and timber processing facilities.
The new technologies needed to extract and process the compounds of interest are likely to require a high level of initial investment that will increase production costs until that investment is recouped. This means that there may initially be difficulties in competing with existing technologies producing similar products. Significant additional financial return must therefore be obtained from individual extracted compounds or range of co-products to justify investment.
Development of a wide range of wood extracts/metabolite products through improved extraction procedures could help subsidise the cost of co-extraction of low yielding products with significant market potential that did not justify the costs of production in their own right.
Given that many of the raw materials for processing and extraction of metabolites of interest are likely to be derived as co-products of the timber or paper and pulp industry, factors affecting the profitability of these industries will impact on the viability of metabolite extraction. Globalisation of the wood and paper industry is concentrating ownership into fewer organisations which may help stabilise such industries. However, new pulping capacity on the scale required for economic viability in current markets is appearing predominantly in the tropics, from where significant competition may arise for UK-based industries. Thus, the long-term competitiveness of UK industry in this area will perhaps be best served by developing specialist high-value markets for co-products of pulp manufacture.
Traditional markets for chemical materials derived from pulp tall-oil are relatively static. But with improved extraction techniques, it is likely to become increasingly cost-effective to find novel uses for such compounds. For example, the controlled pyrolysis developed by NREL for extracting phenol-containing compounds has overcome some of the contamination problems of previous processes and has stimulated renewed commercial interest in this area. Such developments highlight that a fresh look at this sector can reap significant rewards and commercial interest.
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References
Aaron J. R. (1982). Conifer bark: its properties and uses. 23 pp. Forestry Commission Forestry Record No 110, HMSO, London.
Agro-Ind. (2002). http://www.agro-ind.com/html en/nigeria23.html
AISE (International Association for soaps, detergents and maintenance products) (2003). http://www.aise-net.org
Banks W. .B and Cooper R. J. (1997). Utilisation of softwoods in Great Britain. Forestry 70, pp. 315-318.
CEFIC (European Chemical Industry Council). (2003) http://www.cefic.be
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