Deliverable D3.1.2 Key products of the forest-based industries and ...

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Key products of the forest-based industriesand their demands on wood raw material propertiesIn some cases, it is possible to express property demands with specific values, for instance when themechanical properties of wood materials for constructions have been standardised. Where it has beenpossible to define such threshold values these have been included.In many cases, however, it is not possible to express the product demands in general terms becausethe same type of product may be possible to produce in production lines designed in alternative wayswhich are able to handle materials with different properties. However, it does not imply that the rawmaterial properties in these cases are of less importance, but that alternatives may be developed toallow the use of materials that would otherwise be regarded as unacceptable or not economicallyfeasible. Researchers may develop and producers invest in new processing equipment to deal withthe problem. The associated costs for the investment and sustainability impacts of the modifiedoperation (use of energy, chemicals, person-hours, etc.) have, of course, to be considered. Suchdevelopment may also make it possible to offer the customer a better product or a good enoughproduct at a lower cost or price provided that proper investment is made. Use of especially suitablematerials may, on the other hand, increase product yield, quality, added value, customer satisfactionand reduce material use, transportation, etc. Innovations in new or improved products and processesas well as market supply and demand will continuously change the conditions and bring newpossibilities or difficulties. Some of these optimisations can be performed gradually to adapt to thecurrent situation, others will involve large investment and are performed stepwise after major decisionswhere it may also be an alternative to shutting down the operation.Property variations in the processed materials may, thus, to some extent be dealt with throughoptimisation and investments in the long or medium time frame and through process adjustmentsbased on assessment and measurements and process control in the short term. Even so, it isimportant to bear in mind that product quality and production efficiency are normally improved by useof materials with uniform properties.From this insight, it has been concluded that the property demands in many cases can only beexpressed in a qualitative way rather than quantitative and general terms. An obvious observation isthat the more steps of conversion or processing that are involved in the manufacturing of a product,the more alternatives will be possible and the more difficult is it to define property demands on theinitial wood raw material. It may be rather straight-forward for a board but less so for a wood-basedconstruction element or a paper product in which the wood fibres have been totally restructured.The more the materials have been converted, the more expertise is needed to make a realisticjudgement on the property demands and how allocation and processing can be optimised whendealing with a specific forest resource, production facility and product. This is also to some extentreflected in the character of the chapters dealing with fibre chains, solid wood chains and bio-energychains respectively. In the chapter related to production of pulp and paper, which is more complex andalso assumed to be less familiar to most readers than the other production chains, a brief presentationof relationships between properties of fibres and paper has been added.6
Key products of the forest-based industriesand their demands on wood raw material properties3. Fibre chains3.1 Key productsThe key products selected from the fibre chains and from what materials they are produced arestructured in Table 1, and are divided into:• Graphic products (1a - 1d)• Packaging products (2a – 2e)• Hygiene products (3a – 3b)The list includes a total of 11 key types of converted products produced from 13 key paper types. Inmany cases the paper products are built up by mixing fibres with different properties and othermaterials, in order to optimize quality/functionality and cost/price. Higher cost materials or furtherprocessing (with associated costs) may be used to produce higher quality grades, and vice versa.Some of the paper types are multi-ply materials, where the different layers serve different purposes,for instance to enhance an important property or to reduce costs. The layers are often produced fromdifferent types of pulps, which are processed to optimise the material as a composite.Some basic product properties are common for many of the key products of the fibre chains:printability, stiffness, runability on the paper machine, in printing presses and other converting, etc.The properties obtained in the paper depend both on the fibre raw materials used and the processingof the materials in the production line (equipment and conditions). As the fibres have similar influenceson several properties important for many products, these relationships are commented on separately.3.2 Key demands on wood and fibresThe properties of the fibres, pulp and paper used in the different parts of the production chains arevery important for the product properties and the production efficiency. For paper products, no specificgeneral threshold values can be defined for the materials used along the production chains. Theproperties need to be suitable for the product and the process and they also have to be uniform andpredictable.When the basic functionalities of a pulp or paper product are fulfilled, the uniformity is often said to bethe most prominent “property”. Uniformity shall in this context be understood as constant propertydistributions in time, not as homogeneous. When a printer has adapted his press to a certain paper,he wants to get paper with the same properties all the time. And this constancy should preferably startwith the wood raw material fed into the process. Some heterogeneity in fibre properties may, however,often be beneficial: Some long fibres in the pulp will provide good strength of the wet paper sheet onthe paper machine and will improve the runability, but if they are too many, the fibres will start to formflocks and the formation of the paper will suffer. Suitable property distributions are, thus, needed andthey should be reasonably constant in time. If suitable distributions can not be obtained from a singlepulp, it is mixed with pulps or materials to match the specifications. A typical example of this is theaddition in many products of some “reinforcement pulp”, longfibre kraft pulp, to increase strength.7
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