Wood-fibre for future products from Eucalypt papermaking fibres pulp Today, eucalypt market pulps are normally produced from plantation-grown forests and short crop rotations (5-15 R. Paul Kibblewhite years), with each new generation of planted stock giving Principal Scientist, Ensis, Private Bag 3020, Rotorua, New improved pulp yields and fibre qualities. This is a rapid, Zealand global and highly competitive pulp-quality development process, and one which is based primarily on conventional Summary breeding, propagation and cloning technologies. Today, The properties of hardwood (eucalypt) and softwood eucalypt fibre selections target a chip density of about 550 (Northern, radiata pine and Southern) papermaking fibres kg/m³ to give optimal fibre coarseness, length and collapse of today are first described. Also outlined are the different resistance, and in turn desired sheet bulk and tensile roles of these two fibre types in papermaking furnishes, strength, surface and optical properties, and uniform together with their strengths and weaknesses and how they formation. Eucalypt fibre qualities vary widely with might be enhanced or overcome in the short-term (10 – 20 species, rotation age and growing site (Figure 2) (1, 3). years). When the crystal-ball horizon is extended to 50 years, short rotation radiata pine trees with greatly enhanced fibre property uniformities are envisaged, together with an ability to develop a wide range of new products from pulp.
Wood-fibre for papermaking: The next 10-20 years Introduction The fibre properties of length, coarseness, collapse resistance and number/g (Figure 1) determine the suitability of a pulp fibre-type for the manufacture of specific papers. Market kraft fibre types are naturally divided into softwood and hardwood groups with the latter being roughly one-third the length, coarseness and perimeter of softwood fibres. Both fibre-types can, however, have similar collapse resistance and wall thickness values, but very different numbers/g (1, 2).
Figure 2: Eucalyptus globules, a premium eucalypt fibre- type (3).
Some expected eucalypt fibre production directions over the next 10-20 year period are: • Conventional breeding and propagation technologies • Short crop rotations • High forest productivity and disease resistance • Emphasis on low cost, rapid propagation procedures, and screening tools
Wall area ∝ Coarseness • Genetic modification of lower priority Number ∝ 1/(wall area x length) • Within-tree property variation with height and radial Width/thickness = Fibre collapse (in dried sheet) direction unimportant? Perimeter/wall thickness ∝ 1/(Wood density) ∝ Collapse Softwood fibre qualities The situation is very different for the three recognised Figure 1: Fibre property interrelationships (1). softwood fibre types (Northern of premium quality, radiata pine and Southern) with their long crop rotations (20 – 80 A papermaking furnish can consist of a range of different years) and diverse end-use options. Fibre dimensions, pulp- and fibre-types to optimise processing and relative numbers of fibres and fibre property distributions, manufacturing costs and product quality. Softwood fibres can be very different (Figures 3, 4) (1, 2, 4). Northern (radiata pine) give reinforcement, runnability and softwood fibre types are of equivalent length with slender toughness, while hardwood (eucalypt) fibres give bulk, fibres of low coarseness, microfibril angle and surface and optical properties, and uniform formation to a hemicellulose content compared to those from radiata pine formed paper (2). and Southern species. Hence, numbers of fibres are higher in the Northern pulps, and refining requirements are lower, but crop rotation ages are very much longer.
Appita 2007 - 203 Printing and Writings, Tissue, Glassine "Long, slender, low coarseness fibres" ⇑ Commodity Grades ⇓ Fibre Cement and others?? "Tough, absorbent fibres - Longer, 123 80 52 slender, high coarseness fibres"
Figure 3: Softwood fibre types with relative numbers of Figure 5: Adding value through fibre quality fibres indicated (2, 4). improvement to produce specialty rather than commodity products.
125 110 100 76 Figure 4: Fibre coarseness distributions by softwood fibre-type (4). Figure 6: New Zealand ultralow, low, medium and high categories of radiata pine market kraft (2, 4). The papermaking qualities of radiata pine market kraft pulps have progressively improved over the past three decades through wood/chip segregation, pulp fractionation and conventional breeding, hybridisation and cloning. The goal has been to add value through radiata pine pulps being utilised in the manufacture of paper grades for which they had previously been unsuitable (Figure 5). Four categories of radiata pine market kraft, specifically for tissue, printing and writings, and fibre cement composites, have resulted from wood and chip segregation prior to pulping (Figure 6). Pulp fractionation has been successful in separating fibres by length but the challenge of the future is to achieve this by fibre collapse (Figure 7). This would allow highly uniform, at present unavailable, pulp types to be produced from radiata pine and southern species. Finally, it is suggested that trees could be bred for low coarseness while retaining wood density and fibre Figure 7: A softwood market pulp with very non-uniform length (Figure 8). This is unlikely to occur while wood rods and ribbons. This would be greatly improved through costs require the pulp mill to be a residue user only. It is fractionation by fibre collapse. suggested that “change” is required for softwood pulpwood regimes and fibre quality improvement programmes to be cost-effective.
Appita 2007 - 204 Latewood Earlywood
Rod-like Ribbon-like Same coarseness Thick wall Thin wall, Figure 8: Same wood density but very different fibre Small perim Large perim coarseness and numbers (1). Uncollapsed Collapsed Wood-fibre for papermaking: The next 50 years
Who knows? For today’s commodities, tissue, sanitary Figure 9: Earlywood and latewood fibre property and packaging products will possibly continue in one form combination or another, whereas the future for junk-mail, newsprint, communication and hard-copy grades is probably limited. Today’s specialty pulp grades such as cement reinforcement pulp probably have a future, with the emphasis being on sustainability.
Wood-fibre for future bio-products from pulp: A 50-year horizon When the crystal-ball horizon is extended to 50 years, short rotation radiata pine trees with greatly enhanced fibre property uniformities are envisaged, together with an High coarseness Low coarseness ability to develop a wide range of new products from pulp. Few fibres Many fibres Finally, we will be able to both design and select fibre Small surface cm²/g Large surface cm²/g property combinations, and produce new innovative Same Chip density products, from a wide range of modified radiata pine Same Wall thick/perim genotypes (5). Compared to today, fibre property Same Collapse population distributions will be greatly narrowed, and fibre property relationships will be changed. As an example, Figure 10: Low and high coarseness rod-like fibre genotypes could be selected for highly uniform property combinations. populations of either low or high coarseness fibres with Rod-like populations Ribbon-like populations similar lengths and perimeters, giving very different wall Low coarseness High coarseness Low coarseness High coarseness thicknesses and collapse resistance. Furthermore, we Many Few Many Few Low collapse Low collapse High collapse High collapse envision that some fibre characteristics will be very Low or high MFA Low or high MFA Low or high MFA Low or high MFA different to what we observe within the range of Long or short Long or short Long or short Long or short endogenous variation. A number of fibre property Figure 11: Four plus possible fibre property combinations are theoretically possible, as well as the combinations. range of bio-products that could be made with them.
However, in order to achieve this we need to develop The future is for purpose-grown, short rotation softwood appropriate assay procedures – preferably at the nano- and or hardwood (eucalypt) forest crops to give desired fibre micro-levels, to take advantage of developments in plant property combinations for sustainable designer products. biotechnologies. This will be achieved through genetic modification with a
critical success requirement being the development of Softwood and eucalypt fibres of the future will come from assay procedures for screening genotypes at age 3 months purpose-grown short rotation pulpwood regimes (5 – 10 or younger. In addition, such a product development years) giving highly uniform fibre property populations, programme from pulp will need to include: fibre-property- earlywood- and latewood-type pulps, and a wide range of combination research and development, potential product chemical and physical fibre property combinations. The identification processes, fibre property combination range of possible fibre property combinations could selection and supply, and product development. include those in separate earlywood and latewood pulps Associated constraints will include: costs, sustainability (Figure 9), and low or high coarseness rod- or ribbon-like and the green-house-effect. fibre combinations (Figures 9, 10).
References 1. Kibblewhite, R.P.: Designer fibres for improved papers through exploiting genetic variation in wood microstructure. Appita 52(6):429-435(1999).
Appita 2007 - 205 2. Mansfield, S.D., Kibblewhite, R.P and Riddell M.J.C.: Characterisation of the reinforcement potential of different softwood market kraft fibre types in softwood/hardwood pulp mixtures. Wood and Fiber Science 36(3):344-358(2004). 3. Kibblewhite, R.P., Johnson, B.I. and Shelbourne, C.J.A.: Kraft pulp qualities of Eucalyptus nitens, E. globulus and E. maidenii, at ages 8 and 11 years. New Zealand Journal of Forestry Science 30(3):447-457(2000). 4. Kibblewhite, R.P.: New Zealand radiata pine market kraft pulp qualities. PAPRO-New Zealand Brochure, July 1989. 5. Campbell, M.M., Brunner, A.M., Jones, H.M. and Strauss, S.H.: Forestry's fertile crescent: the application of biotechnology to forest trees. Plant Biotechnology Journal.
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