Fraunhofer Institute for Wood Research WoodTreat:
Recycling contaminated waste wood for a circular bioeconomy
Wood is a valuable renewable resource, often treated with chemical preservatives to extend its service life. These treatments protect against insects, fungi, and weathering — but once the wood becomes waste, they pose a major challenge. Large volumes of treated waste wood, especially from dismantled roof structures, cannot currently be recycled. Contaminants from old preservatives prevent safe reuse and typically lead to incineration in Germany under the Waste Wood Ordinance. WoodTreat addresses this challenge. The project aims to process contaminated solid waste wood so that pollutant free secondary raw materials can be obtained. After removing the outer layers, a beam should be reusable as a clean beam. Waterjet technology is preferred to avoid removing nails and screws beforehand. WoodTreat strengthens the circular economy, reduces environmental impact, and supports the sustainable use of wood as a renewable raw material.
In Europe, wood waste is classified into several categories. The highest category — Class C or, in Germany, Waste Wood Category A IV — encompasses wood that has been heavily treated with wood preservatives, or wood that is at least suspected of being contaminated with such preservatives. It contains chemicals such as pesticides, biocides, or fungicides used to increase durability. These old chemicals can pose a risk to the environment and human health. As a result, this wood is currently not recycled but primarily incinerated.
With increasing wood use — for example through the “New European Bauhaus” — even more treated waste wood will arise in the future. Although such treatments extend the lifespan of wood, this wood will eventually become waste and must then be disposed of. However, old and no longer permitted wood preservatives are particularly problematic — they can pollute the environment and endanger human health. There is therefore a strong need for improved remediation technologies and efficient cleaning methods for contaminated beams.
Simultaneously, existing contaminants (chemical treatments, heavy metals) currently make wood recycling very difficult. Further research into cleaning and processing methods is therefore necessary. Category A IV waste wood can consist of various wood species and products with very different levels of contamination. This necessitates complex measures and requires solutions for both the circular economy and environmental compatibility.
The main goal of WoodTreat is the development of processes for extracting “clean” secondary raw materials from waste wood that is heavily contaminated with wood preservatives. These same processes should also be transferable to wood with lower contamination levels.
A key objective is the development of an automated online characterization system.
It should be able to reliably distinguish between contaminated and less contaminated wood — online and in real time. This would significantly simplify the sorting process.
Furthermore, in the project we are reviewing existing laws and regulations and developing recommendations for future regulations. This is because the legal framework must support the upcycling of cleaned, processed waste wood. The German Waste Wood Ordinance does not currently provide for the reuse of contaminated wood, even if it has been verifiably cleaned.
The WoodTreat approach: From waste to valuable material
WoodTreat pursues a multi-stage cascade approach for heavily contaminated wood waste from the consumer sector. In the project, we are developing processes that remove contaminants from the wood and recover high-quality secondary raw materials. These can then be incorporated into new products.
The research results will be tested and validated in seven pilot trials. In this way, WoodTreat ensures that the processes will also work in industrial practice.
The advantages are clear:
- Reduced consumption of fresh wood
- Reduction of non-sustainable disposal methods or incineration
- New high-quality products made from secondary materials
- Strengthening of the circular economy
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