- A database of primary and secondary compounds found in alder, ash, aspen, beech, birch, cherry, Corsican pine, Douglas fir, larch, oak, poplar, Scots pine, Sitka spruce and willow has been created. To improve accessibility the data has been tabulated, and using hyperlinks, can be searched by either species or chemical of interest.
- The information was extracted from commercial and in-house databases and included bibliographic databases (e.g. Dialog with access to over 500 scientific databases), phytochemical databases, research papers, conference proceedings, books, unpublished reports and company literature. In total over 37,000 records published over the last three decades were gathered and interrogated.
- Data extracted from these records included, the ethnobotany of the tree species, the metabolites that can be derived from trees and the tissues from which they were extracted (e.g. bark, leaves, heartwood, roots), their yields, properties, hazards, CAS No.'s (compound-specific identifier codes), extraction methodologies, approaches to transform and 'add-value' to the metabolites, and current and future market potential for these tree products.
- Despite the apparent abundance of information on metabolite structure and activity, there is a relative dearth of data on the yield or variability in yield of metabolites for the UK's tree species upon which to base an assessment of economic potential In the short-term, basic research is required to quantify the impact of tree genetics and environmental factors on yield and hence the final quality of the tree product.
- The search for novel applications for the tree metabolites has been augmented by computer-aided Quantitative-Structure-Activity-Relationship modelling (QSAR). This is a technique increasingly adopted by industry (e.g. food and pharmaceutical companies) in their search for new products (e.g. sweeteners, pharmaceuticals, protein polymers, catalysts, pesticides etc). Using computer-aided molecular design software and expertise we built 3D-representations of key tree metabolites. We then incorporated these simulations into our models and were able to predict the potency of tree metabolites as insecticides and antimicrobials, and consequently identified possible markets for these materials. All this was achieved without the need for expensive, laborious and technically exacting laboratory screening tests.
- Traditional (e.g. paper and naval stores) and emerging markets (e.g. adhesives, detergents) for tree products have been identified. Those industries exploiting tree metabolites (e.g. cellulose) as raw material are experiencing a 'renaissance,' with a surge in the development of new tree-derived products with many different applications. For example, the Austrian company Lenzing extracts cellulose fibres from beech by a chemical pulping process, for use in textiles and industrial processes. This utilises around 40% of the tree biomass. Lenzing has sought to add value to the wood feedstock by utilising biomass as a source of fine chemicals; so far they have been able to utilise a further 10% of the harvested biomass through this route with the remainder used to produce energy. This is a significant improvement on typical tree biomass utilisation rates of around 35-40%. Work is also progressing to develop phenol-formaldehyde resins (PF) from wood, which have particular uses in the heat-set adhesives used for wood board production (ply-wood and stranded boards etc). US research has demonstrated that PF resins derived from softwood cost around 25% less than synthetic resins. There are also advantages in reduced setting time, which speeds up the manufacturing process. These developments reflect a determination to focus leading-edge expertise on high value markets to justify the costs of extraction and maintain a competitive edge for tree products.
- Prominent amongst the reasons for the failure of many wood extractive ventures has been the non-specificity, inefficiency and environmental hazards posed by the techniques used to extract the tree metabolites. Newly-developed techniques such as super-critical gas extraction promise to provide, efficient, specific, environmentally- and 'process-friendly' (production of dry residues that can be used to generate heat and power) methods of obtaining the value-added products at competitive cost. Further research into extraction technologies will not only maximise the range of products that can be obtained from wood, but will also be able to fine-tune the extraction process to improve purity, as well as causing minimal environmental damage.
- The review also identifies new opportunities to transform tree metabolites into value-added products. For example, cellulose chemistry has come to a technological turning point with a number of new cellulosic products emerging with novel and wide-ranging properties. These products offer improved performance and environmental (e.g. biodegradability) advantages over competitor materials. Potential markets include selective adsorbents and traps, air-conditioning systems, catalyst support materials, controlled release materials, use in polymer blends and as a co-polymer. R&D support is required to fully evaluate the generic potential of these materials and thereby accelerate their adoption.
- Finally, there are many interacting factors that will influence the success of adding value to trees, ranging from the yield of the tree metabolites to the chances of displacing competitor products in the market. If undertaken in isolation, lengthy searches for exotic metabolites, or elegant schemes for isolation, or screening for possible uses for the isolated substance, are likely to yield good science but zero utilisation. The successful exploitation of the knowledge contained within this wide-ranging review will require the collaboration of experts across the sector including foresters, biologists, chemists, agronomists, industrialists and business economists. We recommend that this process begins by disseminating the review's findings through consultation, direct or indirect (e.g. world-wide web), within the sector.