The Academy Lecture

W.E. Hillis

Wood Science in the Future.

International Academy of Wood Science Meeting 2006, november 13-16, 2006, Melbourne, Australia

• Presentation of W.E. Hillis

It is most important to strategise on future developments but this is most wisely done with some reflection on the past. I have been incredibly fortunate to work in the scientific explosion of the post World War II period. Over this 60 year period the huge amount of scientific knowledge has driven specialization and sub-specialization so that quick and effective communication has become increasingly important.

The first part of my talk will be briefly of reflections on developments that were made from 1947, the year when I published my first research paper. I will then incorporate some of the key developments that may relate to forestry from Nobel Prizes and the obvious developments from the Marcus Wallenberg Prize and then attempt to challenge us by our current demands. It is often said that if you stand on the shoulders of our predecessors you can see further. If we stand on the shoulders of our giants, how far would we see and where would it take us?

The tallest giant in Wood Science is Prof. Dr Franz Kollman who founded our Academy 40 years ago. Amongst its objectives were the co-operation of many fields of science to establish a platform for discussion, and to attract, particularly young, gifted researchers and technologists. The recent review by Prof. Dr Anders Bjorkmann gives the tasks of IAWS which are in fact the objectives of this meeting.

I shall try and broadly identify and categorise the endeavours that face us under the eight categories of

1. Demands for wood beyond 2006
2. Wood resources
3. Choice of species, including genetics
4. Growing and harvesting
5. Methods of assessment
6. Processing and reduction of waste
7. Recent developments
8. Future developments

My first paper published in 1947 was entitled « Manna of Myoporum platycarpum as a possible source of mannitol Â». The research for this was conducted in the latter part of 1944 when we were searching for pharmaceuticals, in this case mannitol, for the microbiological testing of disease in soldiers fighting in Papua New Guinea. To reveal the development of wood science and technology over the past 60 years, one must recall that it was early in the 1940s that the study of gross anatomy of many woods was commenced to understand their formation, behaviour and to assist their identification. In the same issue in 1947 was an article by Dadswell et al. titled « Extension of the Card-sorting Method to War-time Problems in Timber Identification Â». At the same time physical testing of various Australian woods, and structures made from them were done to ascertain their strength and behaviour, their chemical and physical characteristics were determined , sawing research on eucalypts was done. Importantly, CSIRO and industry continued to develop pulping and paper making from eucalypts. These species with their small fibres, opaqueness, good bulk etc. have since proved to be very suitable for paper manufacture. Also wood adhesives from wattle tannin were developed to overcome a shortage of phenolic resins.

In those days, calculations were assisted not by calculators but by a slide rule, which is a linear form of logarithms. Digital computers were first developed in the 1940s. The one at Melbourne University in 1945 occupied a large room to contain the vacuum tubes which were eventually to be replaced by transistors. They were very expensive. Kilby fabricated the first integrated circuit - the chip - in 1958 and was awarded the Nobel Prize in year 2000.

It is interesting to reflect on the other articles in this 1947 volume. There were key articles on pest control, categorization of wood, the structure of wood, properties of wood, use of extracts from wood and wood products. Interestingly there were articles on pest control with DDT and in particular insecticide trials. The year later in 1948 Paul Hermann Muller received the Nobel Prize in Medicine for his discovery of DDT as an efficient insecticide, During World War II and immediately thereafter, DDT made it possible to master not only typhus epidemics but also to combat other insect-transmitted diseases such as malaria. The World Health Organisation estimates that during the period of its use approximately 25 million lives were saved. Today DDT is a banned chemical because of its environmental effects. Are the developments of today going to be the scourge of tomorrow?

In addition to the development of pulp and paper manufacture from eucalypts by Cohen, Higgins and others in the 1950's, other basic studies were progressing. The first working Electron Microscope was designed in the 1930's. However, it would take more than 50 years before this was recognized by a Nobel Prize. Indeed in the 1950s I worked in the same room as Wardrop, his early model Electron Microscope and X-ray equipment. He continued his studies to unravel the cell wall structure of wood fibres, microfibril angle and other features. Much of our present understanding of wood resulted from those studies.

For centuries wood has been an object of beauty, whether for high quality furniture, carvings or the intricate items of marquetry which were given as gifts of distinction. Now, Wood Science can improve utilization of wood for modern purposes. It will develop on the foundations made by present day giants.

The Marcus Wallenberg Prize was first awarded in 1981 to recognize single significant and pathbreaking achievements important to the development of the forestry and/or the forest products industries and their sustainability. All aspects of these industries have since received awards. Early recognition was given to research on nutrition for fast growth and aerial pollution. Then it was given to methods to assist tree breeding, and more lately genetics. Pulping, including fungal degradation, and bleaching have been recognized over several years. Lately, attention has been given to paper machine development for increased speed and better products and to be more environmentally friendly. Most recently the Prize has been devoted to wooden structures, quick quality determination of wood and fibre and most recently effects of climate change. In this period the Nobel Prize in chemistry was awarded to the most basic studies of nucleic acid complexes and the development of NMR. There has been a shift to the understanding of the fundamental features of the formation of substances. Furthermore, there has been an increase in the speed, accuracy and efficiency of changes to meet existing conditions and market demands.

Demands for Wood beyond 2006

In the last 20 years global population has increased from 4.8 to 6.5 billion and increasing, mainly in less developed countries, some of whom supplied wood to the international market. This increase in urban and rural areas still results in the need for more agricultural land for food and firewood. As well in some countries the increasing standards of living has resulted in increasing environmental and recreational pressures. There is increasing demand for basic resources, particularly renewable resources of which forests and plantations are the most important and versatile. Currently plantations supply one-third of wood produced. Not only do they supply materials at a very low energy cost for construction and pulp, they can provide climate control, carbon trading and reduce dry land salinity. Also some species provide chemicals such as resins and tannins for general or specific uses.

Increasingly, wood of required quality is becoming an export item whether for appearance wood or construction timber. Paper is an essential and significant commodity which consumes much wood. As an example, if everyone in Australia, with a population of 16 million, used 20 sheets of toilet paper daily more than 480 tons of pulp wood would be required to meet that need. There is an urgent need for Australia to increase its forest resources.

CHALLENGES

In what areas should Wood Science be creating discoveries and visionary statements now to provide the future global demand for resources that will be converted efficiently to products of required quality?

As forestry affects all the properties of wood that is formed it must receive the first consideration.

Wood Resources

In the past, the trees used for wood were of large size. Future wood resources will be of two major types. One, a high-value, low-volume of specific properties (eg appearance) from mature native species in different countries. Their value will need to withstand high transport costs to processing centres. The other type will be fast-grown, high-volume, low-value with specific properties for particular uses. Wood Science will strive to increase the value and application of both types through more efficient processing and utlisation, particularly the latter, for wider more valuable markets. The high-value uses of both groups are often diminished by defects during growth, conversion and application.

Choices of Species including Genetics

The future genera planted in existing forest areas will depend on site availability, growth rate and the properties required for appearance or wood for construction or pulp or for chemicals. The most likely major species will be from the Pinus, Eucalyptus and Acacia genera and others. The most productive sites will become increasingly limited due to agricultural demands, water availability, soil suitability etc. Further costs will involve fertilizer, weed and pest control, to assist growth rates and early harvesting to supply needs for routine applications.

Mean Annual Increment is a most important criterion in the selection of a species. However the end-use of the tree will determine species selection.

Significant improvements have already been made with tree breeding, hybridization and cloning to improve growth rate and wood properties, such as stiffness, for specific markets. Watson and Crick in 1953 revealed the details of genetics with their vital understanding of the DNA of the chromosomes of the complex gene. We now have the complete genome of humans. Greater attention must be given to genetic improvement of trees. Curly grain and fiddle back grain, required for high valued uses, is genetically inherited.

Significant developments in genetic development of forestry and forest products and the selection of elite material have been made. Important genes that control tree growth rate and wood properties have been discovered. With the identity of these markers, genetic modification for a required purpose is possible. In 1983 the Nobel Prize was presented for the discovery of « mobile genetic elements in plants Â». In 1994 Namkoong received the Marcus Wallenberg Prize for his contributions to quantitative population genetics, tree breeding and management of genetic resources. Kremer was awarded the 2006 Marcus Wallenberg Prize for discovery of the genetic diversity of Pan-European oaks. From this work there will be a major platform to facilitate decisions about conservation and management of forests.

Growing and Harvesting

In 1991 Donald Marx received his Marcus Wallenberg Prize for the development of selective mycorrhizal inoculation of tree nursery soils which greatly increases the growth and survival rates of conifer seedlings used in the reforestation of inhospitable soils.

The attention given to the use of mixed species in plantations and silvicultural practice enables maximum tree growth of optimal form for the purposes intended. Spacing between trees affects not only the size and extent of branches but also the properties of wood around the trunk whether it be growth stress, reaction wood, brittle heart etc. These changes, which are initiated in the differentiating cells in the cambium, affect the utilization of wood.

In Australia the wood of many native species is of moderate to high durability of medium to high density and strong. Until recently European and American building practices and codes were used resulting in building being over-designed and timber being wasted.

Formerly large trees were felled by axe or chain saw, cut into smaller sizes, hauled to the saw mill, cut into boards and sorted into various quality grades. Future forest resources will be increasingly plantation, which require monitoring for end-use. The latest harvesters are now sophisticated and computer-linked. Before felling the tree they can collect data of diameter, volume and wood quality at different heights. After felling, they strip the bark, assess the log for shape, length, diameter and then cut and stack into grades of quality.

Methods of Assessment

As forestry is a multifaceted, long-term activity affecting all the properties of wood it requires early assessment of all activities particularly those applied for a required property.

Quality must be monitored at all stages to ensure the uniformity of the product. Also grading and segregation must be appropriate to end-use requirements. In the early stages of processing ultrasonic techniques, and in particular circumstances X-ray, can check the dimensions of board uniformity, the existence and the appearance of voids during the drying that will prevent their use in particular applications and for stiffness. The techniques enable the monitoring of strength of components during transport, storage and service. Rapid non-destructive testing assists the choice of the best uses for wood.

In 1982 the second recipient of the Marcus Wallenberg Prize went to Ricardo Foschi for his work in mathematical models that predicted mechanical performance of wood structure. This has highlighted the opportunities to promote safety and economy in wood-based designs. In 2000 the prize was awarded to Robert Leicester for his creation of design codes for wooden structures to take account of variability and reliability of wood as a structural material under various conditions, including fire. Rapid non-destructive testing of wood quality will ensure the best uses for wood when about one-half is used in the construction industry.

CAT (Computed Axial Tomography) was invented in 1972 using X-ray and is widely used for medical purposes. The inventor was awarded the Nobel Prize in 1970. A similar principle was refined and developed to examine wood.

In 2001, Robert Evans was awarded the Marcus Wallenburg prize for the development of instrumentation and software for the characterization of the structure and quality of wood. The SilviScan systems integrate fibre and density measurement functions using SilviScan X-ray densitometry, X-ray diffraction and tomography in a single instrument. SilviScan measures rapidly density, various properties of the wood fibre, including Micro Fibril Angle. MFA and density strongly influence stiffness, important in construction wood. Cellulose crystallite width can indicate the microstructural characteristics in the cambium.

SilviScan can screen families and clones of young trees and possibly seedlings, so that genetic modifications can be assessed. It can monitor tree breeding and the effect of environment and silvicultural procedures on wood quality traits for particular uses.

The recent introduction of the scanning cellular UV microspectrophotometer enables the localization and measurement of lignin and phenolic extractives during their formation and removal. Near Infra Red spectroscopy predicts total phenolic content, which is related to heartwood formation, natural durability and their affect on adhesives. Gamma Ray Spectroscopy assists ash analysis.

Heartwood formation from sapwood varies between genera. The regularity of initiation of formation indicates genetic control but in some species this can be influenced by environment, water availability and forest practices. Heartwood and its extractives impart the colour required in high quality appearance woods. With short rotation, fast-grown woods colour will require the use of durable colour stains and durability conveyed by preservatives. The increasing proportion of sapwood produced will require care at all stages against decay and discoloration. On the other hand, the lower extractives content in sapwood does not interfere with bonding in wood-wool cement boards used in tropical areas.

Further research on bark - occupying 5-15% of a cross-section of the tree - is needed to fully utilize its properties. Some barks contain useful chemicals. The aqueous extracts of Acacia mearnsii are widely used for tanning to yield leather as well as wood adhesives. Aqueous extracts from the bark of Pinus spp. can provide high performance adhesives to reduce reliance on oil and can also provide anti-oxidants.

Traditionally many chemicals have been obtained from bark or wood. Collection of many of them is no longer viable or they have been replaced. Rubber collection from incisions in the bark of a Hevea sp. remains important as also oleorosin from various Pinus spp. Turpentine and wood rosin are obtained as by-products of the kraft pulping of Pinus spp. with turpentine condensed from the relief gases of the chip digester. The alkaline waste liquor is fractionated into various products including rosin and fatty acids. The use of the latter is increasing and developed into different products.

Processing and Reduction of Waste

In contrast to most other resources, wood is produced at low energy cost and this advantage must be returned in its conversion to products. Attention is now being given to cutting and abrasive methods to improve dimensions and surfaces of materials containing stressed material, interlocked and spiral grain.

Small-sized sawn wood waste is being converted into finger-jointed larger-sized material and for various types of particleboard. The surface of glued products require advanced surface engineering processes to enhance adhesion, particularly with hardwoods, such as Australian, under conditions of high humidity. Extractives can migrate quickly blocking cell cavities, preventing interlocking, curing and setting and enabling wettability. Moreover some can oxidize quickly to affect surface properties. The fundamentals affecting the long term bonding of high density hardwoods require attention. Several products require further development of faster low-cost adhesives, more tolerant of moisture differences in the raw material and its surface chemicals and for external use. These requirements are particularly needed for the manufacture of plywood from veneer, particularly thin veneer, when extractives can discolor the surface and where the color of the glue line is important. The pliable nature of veneer assists the development of plywood etc. for many high-value items.

In 2005 Pizzi was awarded the Schweighofer Prize for his development of « Wood Welding Â». In this process, available equipment can be used to apply rapidly alternating mechanical friction to two wooden surfaces under pressure. The joints created without adhesives are suitable for interior use. It is receiving increased chemical and physical attention.

Renewed attention to the properties of the components of wood will assist its processing. Steaming has long been used for the production of bent wood in furniture. The softening of lignin in wood chips (such as with ammonia) could reduce energy demands in groundwood pulping

Improved surfaces of radiata pine have been achieved by treating them with delignification chemicals and then polymer has been applied to provide a good surface for future coatings to provide stability and appearance.

Eriksson and Kent Kirk were awarded the Marcus Wallenberg Prize in 1985 for research on the fungal degradation of wood. It opened up a new approach to the biological utilisation of forest resources. Fungi are now applied to wood chips to provide stronger pulps and energy savings during thermomechanical pulping. Can fungi selectively remove hemicelluloses and/or lignin to obtain cellulose fibres to strengthen transparent plastics or coatings ? Can the phenolic groups of lignin be combined with polyphenols to stiffen wood, or to improve adhesion or the long-term bondability of high density hardwoods ?

Recent Developments

Over the past 15 years, the development of innovative micro-wave technologies, have significantly facilitated knot detection, timber drying processing and added value to wood products. They have assisted drying, reduced stress in logs and the formation of voids. Microwave technologies enable the rapid bending and shaping of components notably from native hardwoods for furniture manufacture. The treatment changes cellulose crystallinity, which occur with thinning and fertilizer treatment of eucalypts and stiffness but not the amorphous nature of lignin.

Notably, high intensity microwave increases the porosity and expands the wood to enable the penetration of different types of resins. The subsequent heat-pressure of the boards yield a superior product « Vintorg Â» of high strength and dimensional stability. Alternatively the porous wood can be treated with preservatives.

Future Developments Required

With some species, injury of the cambial region can cause some cells to form a different class of polyphenols, often in large amounts, normally found. With eucalypts, injury causes the formation of leucoanthocyanins (kino) instead of the different class of ellagitannins. At the sapwood/heartwood boundary the extractives formed at the heartwood are larger in amount and often different from those in the sapwood. Obviously the cellular changes in the cambium resulting in such changes will be easier to study than those at the sapwood/heartwood boundary.

On the other hand the formation of extractives can be very specific in the sapwood close to the heartwood boundary. The formation of pure robinetin at some pit membranes between parenchyma and vessels in Intsia spp. and inorganic salts in Cardwellia spp. is an example. With further advances in enzymology it will be possible to prepare pure complex chemicals from simple carbohydrates without by-products and waste.

Conclusion

Over the past 50 years, wood science has developed from the characteristics of forest resources to many important technology products. Wood is a versatile material and with a greater understanding of its formation more efficient materials can be developed.