New markets and applications for native hardwood species
New approaches to silviculture call for a maximum increase of biodiversity in forests through the creation of mixed forests. Lower Saxony, for example, strives for a 65% share of deciduous trees. This contradicts the ratio of consumption of lumber, which in Germany is currently met with about 80% of coniferous lumber. Against this background, it will be necessary to use deciduous trees more extensively to meet future demand.
The aim of this project is therefore to develop deciduous lumber-based products and make those, in close cooperation with partners from the forestry and timber industry, available to the consumer.
It is imperative to utilize the already existing, but under-utilized, potentials of existing deciduous lumber inventories efficiently and economically.
The following closely related topics were the focus of the project:
1) The use of deciduous lumber for structural purposes:
The aim of this work package was the use of lumber for gluelam. The focus was the development of grading criteria and the mechanical quality sorting procedure for gluelam and single lamellas. 2) Deciduous lumber for exterior uses. The aim of this work package was an increased durability on native wood species on the one hand side by using conventional wood preservative systems and on the other side biocide free wood modification processes. Another key aspect is the Creosote free treatment of railway sleepers. 3) The use of deciduous lumber for wood based composites: The aim of this work package was the use of beech for laminated veneer lumber (LVL)
Through the close working relationship with the wood processing industry, it will be possible to develop new deciduous-based end products and thus make a significant contribution to improving the supply of raw materials as well as improving the economic situation of the forestry and wood industry.
In subproject 1, a quality grading of the wood was carried out and in this context, various aspects were examined in detail (for example the measurement of grain angle). In addition, different strength properties were investigated as a function of the size of the test specimens. On maple and ash different types of strength properties (transverse pressure, transverse tensile, tensile and compressive strength) were tested. In addition to the objectives formulated in the application, work was carried out on the economic viability of hardwood for load-bearing structures.
In subproject 2, on the one hand, wood preservative and wood modification systems were examined, on the other hand the possibility of impregnation of railway sleepers with chromium-free wood preservatives were tested. The wood preservative treatment with conventional preservative systems was not successful. Although the preservatives penetrated into the wood in sufficient quantity and depth, the effectiveness has not been demonstrated. The reasons for this are not yet known. The studies on wood modification (thermal modification in combination with melamine resin treatment) led to less successful results with beech than with poplar. They also showed that the process parameters must be optimized for each type of wood. The detailed studies on the influence of different process parameters will make optimization possible in the future faster and more efficiently. The results of the impregnation of railway sleepers of chromium-free protective salts showed that a treatment is possible, but the crack formation is critical. Possibly an additional hydrophobing component would be necessary to influence cracking in a positve way.
In subproject 3, the work plan has been adapted, since the originally proposed preservative systems did not lead to satisfactory results. Modification of veneers for the production of LVL with phenols, on the other hand, is very promising.