How to process secondary wood materials into fibres?

To produce fibres from virgin wood, the wood is first chipped and then softened using moisture and heat. In the following step, the wood chips are disintegrated into fibres (defibrated) through mechanical impact. However, defibrating fibreboard or solid waste wood is a true challenge. In the case of fibreboard, mechanical treatment can easily shorten the fibres, resulting in reduced strength properties of the new panels. Solid waste wood, compared to virgin wood, has a rather low moisture content, making it brittle and leading to shorter fibres.

A solution can be found in adapting the existing defibration technology. In the project, the thermo-mechanical pulp (TMP) process was modified to handle not only virgin wood but also post-consumer fibreboard and solid waste wood. All the developed modifications can be integrated into existing machines making recycling a viable option for many fibreboard manufacturers. This is because the TMP process is well-established in the industry, and its costly equipment does not need to be replaced. A new technology developed by EcoReFibre partners involves steam to extract fibres. In this process, chipped post-consumer fibreboard is placed in a reactor and pressurised with steam. When the pressure is released, the material partially disintegrates and the defibration is completed through mechanical impact.

Various technologies for various needs

It is important to offer a range of technologies for the defibration of secondary wood materials to facilitate fibreboard recycling. Each panel production site has its unique features that need to be considered. By providing multiple options, manufacturers can select the technology that best suits their conditions, regarding existing machines, type of raw material, or plant layout.

In the labs of EcoReFibre partners, recycled fibres are analysed and characterised for their length, morphology and many other properties. Lab panels are produced from the recycled fibres and tested to evaluate their characteristics, such as bending strength. These results provide a vital input for further development and optimisation of the defibration technologies. Additionally, machine learning approaches are harnessed to reduce the number of test runs required.

Not only fibres, but also fines can be produced from waste wood. Compared to fibres, they are smaller, have a rounder shape and are needed, for example, in particleboard manufacture. The technology developed in the project utilises a reactor equipped with an internal agitator that crushes chipped post-consumer fibreboard into fines. To aid the process, water can be added.