limate change, biodiversity requirements and ecosystem conservation raise questions about the future. What types of wood will we have access to in the future? RISE has examined the potential of our third most common tree species, birch, and our third coniferous species, contorta pine, as structural timber.
The Swedish sawmill industry is very dependent on spruce and pine, so RISE has now produced documentation showing how two "new" types of wood could be used in structural applications. The wood species are birch, which is Sweden's third most common wood species, and contorta pine, which is the third most common coniferous species. Neither contorta pine nor birch has been able to be graded and CE marked for structural timber in Sweden or Europe1 before. Using more wood species could broaden the raw material base for structural timber and potentially provide higher strength classes than today. Two recent projects, BizWOOD Småland2 and Konstruktionsvirke - Contorta3 have investigated the possibility of strength grading of birch and contorta pine.
Birch as a sawn product is used in the furniture industry, but the use is currently small and is about 50,000 m3fub4. The birch, which actually consists of two sawn wood species, spring birch (Betula pendula) and glass birch (Betula pubesens), has been tested by RISE through a part of the BizWOOD Småland project. The studies show that birch has a significantly higher strength, stiffness and density than our normally used softwood species. In addition, it shows that it would be possible to sort birch with the same approach as conifers both visually and mechanically. The sorting could provide a high yield and sort out high strength classes, in classes up to C45 for construction timber.
Continuation follows and the results from the project will be co-published together with Norwegian results from tests made at RISE for NIBIO, the Norwegian Institute of Bioeconomy. A report will also be presented to CEN/ WG123/TG1, which forms the basis for an AGR (Approves Grading Report) which is an approval for grading for Norwegian and Swedish birch. When the report is published, it will be possible to grade structural timber from birch.
The contorta pine is Sweden's third most common coniferous tree species and originates from North America, where it can be found all the way from California in the south to Alaska in the north. In this vast natural range, it exists as several subspecies. The Swedish contorta originates in the inner parts of central British Columbia in Canada. Today, we speak of contorta, contorta pine or twisted pine. In its natural habitat in Canada it goes by the names. Lodgepole pine and Shore pine. Contorta pine grows quickly in the right soils in the Swedish climate, with up to 40% better volume growth than our native pine.
In the project Konstruktionsvirke - Contorta, machine manufacturers of sorting machines were given the opportunity to carry out measurements in their own machines on collected sample material. In combination with fracture tests conducted at RISE, setting values were calculated for the sorting machines. At present, one machine manufacturer has had an AGR report approved and the other participating companies have data to produce their AGR reports. Once the machine manufacturers have had their report approved, it is possible for sawmills that use sorting machines from them to sort construction timber from contorta. Results from the project show that contorta pine has both lower bending strength and stiffness than domestic pine, which was expected due to the higher growth rate. However, it should be emphasized that grading could give a high yield for strength class C16, which is good enough for many purposes.
This is an article from our magazine Trävärden, view it here! (Link)
