ReFoRe:
Evaluation and processing of waste wood from the construction industry for reutilization in structural timber components

Project start /

Every year, tons of waste wood accrue during the construction and demolition of buildings. A large proportion of this stems from structural timber components - for example roof trusses, ceiling beams or timber frameworks. At present, most of this high-quality waste wood is directly burned in order to generate energy. The aim of this joint project under the leadership of the Technische Universität Braunschweig is therefore to find a holistic, economical solution for the utilization of structural waste wood in the re-production of load-bearing timber-construction elements. At the Fraunhofer WKI, we are developing a portable analysis device for this purpose, which is intended to enable the minimally destructive in-situ examination of installed wood with regard to possible pollutant contamination - with a particular focus on wood preservatives. The project not only provides a contribution towards ensuring that more waste wood can be reused as a high-quality material in the future, but also supports the development of a sustainable, bio-based circular economy.

The photo shows a section of an old wooden beam next to a box-shaped device that is approx. 60 cm wide and 25 cm high. On the front of the device are two light-emitting diodes and various hose connections.
© Fraunhofer WKI
The compact gas-chromatography unit “GC-FAIMS 2020” from Schumann-Analytics serves as the basis for the development of a portable analysis device for the in-situ examination of waste wood contaminated with wood preservatives.
The photo shows the interior view of a roof truss with exposed, dark-brown wooden beams.
© Fraunhofer WKI | Peter Meinlschmidt
Thanks to the new analysis process, valuable waste wood from roof trusses and other wooden constructions could undergo high-quality recycling in the future.

In Germany, around 8 million tons of waste wood are produced every year. Around 80 percent of this is directly burned for energy production. A more climate-friendly and resource-conserving approach would be to reuse the wood several times before it is thermally recycled (burned). With this so-called “cascade use”, the CO2 contained in the wood remains stored in wood products for the longest possible time beyond the lifespan of the tree.

A significant amount of the accrued waste wood is generated through construction and demolition work: around 2.4 million tons per year. Up until now, this waste wood from the construction and demolition industry has rarely been recycled - neither for the production of particle board nor via composting.

The high-quality subsequent use of structural waste wood is currently being impeded by:

  • Uncertainties regarding possible pollutant contamination through previously used wood preservatives, surface protection, coatings or fire retardants
  • Uncertainties regarding the influences of the previous component life on the mechanical properties
  • Metallic foreign bodies present in or on the wood (e.g. screws, nails, wood connectors)

In collaboration with our project partners, we are developing a holistic reutilization concept for structural waste wood. The fundamental steps are:

  • Chemical-physical analysis of the contaminated waste wood and the development of a new analytical procedure
  • Development of processes for the mechanical removal of metallic foreign bodies and contaminated surface layers
  • Evaluation and classification of the mechanical properties of the waste wood
  • On the basis of a digital strategy: Development of an automatable, economically competitive process for the implementation of the waste-wood cycle

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