Green-glued engineered products from fast growing Eucalyptus trees: a review

The objectives of the work described in this paper were to present concept processing pathways for manufacturing high value, green-glued finger-jointed Eucalyptus engineered products and review existing research related to these engineered products. Additionally, critical knowledge gaps that need to be addressed in future research were identified. Research on four green-glued Eucalyptus products (green roof trusses, face-laminated beams, edge-laminated planks and panels, and CLT) and some of the processing steps involved, was reviewed. The research review showed that green finger-jointing seems to provide good quality bonds and is suitable for roof truss applications. The finger-jointed lumber has very different properties to existing softwood resources—which will make it more resource-efficient to define new stress grades for this wood resource. An engineered product where green Eucalyptus grandis was finger-jointed and then face-laminated before drying to equilibrium moisture content had much lower levels of checks, splits, and twist than products that were not face-laminated. Additionally, a higher material resistance factor can be used for this resource in comparison to the current value prescribed in the South African national timber design code. Material and processing variables for green edge lamination has been investigated and it has been found that high strength bonds are possible. Face bonding quality of dry Eucalyptus grandis for CLT has also been investigated and it was found that excellent face-bonding quality could be achieved when using a clamping pressure of 0.7 MPa and with no stress relief grooves present. Future research on this resource and product type should include studies on the process economics, process integration and durability treatment of green-glued, engineered Eucalyptus products.