Veneer product from fibre-managed plantation hardwood: Final report

Today Tasmania has approximately 235,000 ha of hardwood plantations. The majority of theseare Eucalyptus nitens established for their pulpwood properties and not solid timber products.Over one million cubic metres of E. nitens logs were harvested in Tasmania in 2013-14 and thisis expected to increase significantly in coming years. Given the size of the estate, there isconsiderable interest in finding higher-value processing options, which include engineered woodproducts such as, plywood, laminated veneer lumber and cross laminated timber. Tasmanias veneer products processor Ta Ann Tasmania Pty Ltd, and major plantation growingorganisation Forico Pty Ltd, wish to examine if economically viable engineered wood productscan be made from locally grown plantation hardwoods. Forico manages a significant portion ofTasmanias plantation hardwood estate and exports both woodchip- and peeler logs harvestedfrom it. However, previous studies and Ta Anns initial experience, has shown that there aredifficulties in obtaining viable recoveries of veneer when rotary peeling E. nitens logs grown forpulpwood production. With support from a Commonwealth Grant Agreement, Ta Ann sought theassistance of the University of Tasmanias Centre for Sustainable Architecture with Wood toinvestigate if plantation grown E. nitens can be utilised to produce a stress-graded formplyproduct. In the five plantation coupes investigated in this study, average log volume was higher in a midelevationa coupe which received the most intensive thinning and most effective rainfall.Average log volume was lower in the lowest elevation coupe where trees were not thinned orpruned and the logs had poor form and size, but the wood fibre was of a higher density andhigher predicted stiffness. Total usable veneer recovered for the target product averaged acrossthe five coupes was 30%, although a further 20-25% of veneer was cut to 6 x 3 ft sheet, whichcould be utilised in alternative Ta Ann products. In visual grading most of the long-grain veneerwas assigned D-grade, which is generally regarded by the industry as being suitable for innerply material for panels. There were no clear trends of either veneer percentage recovered, orveneer stiffness by position in the 6 m butt-log, however future studies could examine theserelationship in logs extracted from different heights in the tree. Results also showed that a F17 target stress-grade panel product of 83% E. nitens could beproduced if long-grain veneer of higher stiffness were segregated by Metriguard machine andthen arranged in the panel between native eucalypt faces. These panels were significantlydifferent to panels of 83% E. nitens complied with long-grain veneers of lower predictedstiffness, where many failed to meet the target grade. Stress-grade F17 panels of 43% E. nitenswith veneer of lower stiffness were manufactured, but had to use native Tasmanian oak speciesin the face and sub-face positions to improve panel strength, and achieve the desired grade.The majority of panels in all veneer arrangements tested were limited in stress-grade ratings bythe values attained in perpendicular bending strength, which is determined by the properties ofthe short-grain veneer (veneer arranged perpendicular to a panels longer edge). Unfortunatelyshort-grain veneer could not be assessed and segregated at Ta Anns Metriguard, though theveneer could be improved by peeling logs of higher predicted stiffness. Based on the results from this study and the findings from previous ones it can be concludedthat most veneer peeled from fibre managed E. nitens plantations can be utilised in formplypanels, and that using selection techniques for log stiffness, it should be possible to peel alarger recovery of veneer for use in higher stress-grade rated panel products.