Necessity is the mother of invention: Fraunhofer WKI tests utilization of low-value hardwood for wood fiberboard

Extreme drought, forest fires, storms and pests have severely afflicted German forests in recent years. In order to make the forests more resilient in times of climate change, more deciduous trees are being planted than conifers.

As a result, the shortage of softwood will intensify in the future, whilst the quantity of hardwood will increase.
For the wood-processing industry, a fragmented supply of softwood presents a problem. It therefore makes sense to test the utilization of low-value hardwood species in production in order to counteract supply shortages.

Until now, low-value hardwood assortments have used primarily for thermal recycling. The researchers at the Fraunhofer WKI have now found a solution for material utilization.

“Low-value hardwoods will be securely available in the future. Furthermore, the utilization as a basis for wood-based materials is more sustainable than the use as a heating medium,” says Project Manager Dr. Dirk Berthold, describing the initial situation.

In the “GerLau” project, Berthold and his team investigated the optimization of pulping technology and the production of fiberboard materials. The project partners, the Nordwestdeutsche Forstliche Versuchsanstalt (Northwest-German Forestry Research Institute, NW-FVA) and the University of Göttingen, addressed the potential analysis and the value chain of low-value hardwoods.

At the Fraunhofer WKI technical center, initial experiments on pulping were performed in order to fractionate the fibers using differing methods and to thereby assess the qualities.

The fibers from the hardwood species beech, ash and birch were then processed into MDF and HDF boards using a mixture containing spruce fibers. As a result, the researchers discovered that a substitution of coniferous wood by hardwood of up to 50 percent is possible.

“We were able to show that even commercially available grinding-disc sets achieve good results in terms of fiber yield and size distribution. The fiber qualities correspond to those of pure coniferous wood fibers and are suitable for the production of MDF and HDF boards,” summarizes Dr. Berthold.

In addition, the scientists were able to determine, by means of board production and testing, that the MDF and HDF boards fulfill the quality requirements for the mechanical properties. Furthermore, the MDF boards also fulfill the required hygric properties. Through the use of additives, these properties can also be achieved for HDF boards.

“The utilization of low-value hardwoods in the wood-processing industry for the production of MDF and HDF boards should be possible without major development steps. Adjustments in production are only necessary in preliminary sorting at the woodyard and in an adaptation of the applied additives,” says Dr. Berthold.

The utilization of low-value hardwood species increases planning reliability for the wood-processing industry, even in times of minimal softwood supply. This can have a positive effect on the overall competitiveness of the German agriculture and forestry sectors.

The project “GerLau” was performed in collaboration with the partners the University of Göttingen and the Nordwestdeutsche Forstliche Versuchsanstalt and was funded by the Fachagentur Nachwachsende Rohstoffe e. V. (Agency for Renewable Resources, FNR).

Dr. Dirk Berthold
Head of Department Technology for Wood and Natural Fiber-Based Materials
Fraunhofer-Institut für Holzforschung, Wilhelm-Klauditz-Institut
Bienroder Weg 54E
38108 Braunschweig
Telefon +49 531 2155-452
Dirk.Berthold@wki.fraunhofer.de

https://www.wki.fraunhofer.de/en/press-media.html