Researchers make high-quality building boards from pruning waste without added glue

Now that the housing challenge in the Netherlands is coinciding with ambitious climate targets, biobased construction is in the spotlight. Materials made of natural fibres from local waste streams can contribute to this. Especially if they can be made into building boards without the need for glues or resins of fossil origin. It is possible with the binderless technology developed by Wageningen Food & Biobased Research in the CBPM Development of Sustainable Binderless Product Technology project.

“The coconut served as our starting point,” says project leader Richard Gosselink. Coconuts are cultivated for food in Malaysia and elsewhere. They grow in fibrous shells ('husks') that are burnt as waste or left on the plantation after harvest. Fifteen years ago, they were the subject of the first trials. The fibres were pressed into sheets at high temperatures under pressure. Lignin and other components are released from the fibres in this process. When combined, they act as glue.

Cane, straw and woodchip waste

The exact working of this mechanism was unclear for a long time, and therefore the quality of the board material was also unpredictable when using waste streams other than coconut husks. Moreover, there are not many of these in the Netherlands. That is why the mechanism was unravelled and the technology further developed so that it also works with Dutch local residual and side streams. "In this case, it mainly concerns fibrous residual streams released in forest management or in the food industry," says Richard Gosselink. “Think of pruning waste, wood or leaves. Hemp and miscanthus are also very suitable. This makes the technology interesting for the Dutch and European markets.”

Meanwhile, large amounts of data have been collected on the various available waste streams and on their suitability for making board material with Binderless technology. Its properties are similar to those of MDF or Trespa. Traditional production of these materials uses fossil-based synthetic glue, which often contains formaldehyde. It is a volatile organic compound known to cause health problems. The construction and furniture industries are therefore looking for formaldehyde-free adhesives. “With our Binderless technology, we no longer need any additional glue at all. This is unique, sustainable and healthier. It also saves production costs.”

Predicting the quality of board material

Pending a scientific publication, Gosselink does not yet want to reveal in detail how the Binderless technology works. In any case, it is clear that lignin plays an important role in it. Lignin is the natural glue substance that gives plants and trees their strength and protects them from the weather. In a high-temperature pressing process, this substance is activated and liquefied. However, it only works in combination with other components. “With advanced NMR (Nuclear Magnetic Resonance) techniques, we can see which components play a role in the formation of the adhesive in the panel. We can measure the amount of these components in the raw material, but also in the product. Ultimately, the composition of the raw material or a mix of raw materials determines the quality and properties of the final product.”

Testing board material for properties

In the completed project, some prototypes of building boards were made. Basic properties such as mechanical strength, density, homogeneity and water resistance were extensively tested in our materials laboratory. Fire resistance is also good. This proves that these materials are suitable for making constructional boards, which can be used for e.g. facade cladding, doors, tabletops, kitchen cabinets, etc. They can be sawn and screwed. Structural board materials such as MDF, HDF, HPL, Multiplex and Trespa can be replaced with them.

Meanwhile, a follow-up project 'More with binderless' is being prepared, in which aspects such as lifespan, possible certification and cost price will be calculated. It will also include a life cycle analysis (LCA). Furthermore, it will investigate whether waste streams that are less suitable on their own for this binderless technology can be used in combination with other streams. And how the production process can be further optimised using high temperature and pressure. The follow-up project can count on considerable interest from industry.

About project Sustainable Binderless Product Technology

Development of Sustainable Binderless Product Technology is a project coordinated by Wageningen Food & Biobased Research within the Circular Biobased Performance Materials (CBPM) research programme. The project focused on developing binderless sheet materials from local waste streams. They were tested for several applications. In addition to structural building boards, these included, for example, packaging. Project partners were Enkev, the Forestry Commission (Staatsbosbeheer), the Nature Conservancy (Natuurmonumenten) and the Directorate-General for Public Works and Water Management (Rijkswaterstaat) from the Netherlands and Nextevo from Malaysia. The project ran from 1 January 2019 to 31 December 2022 and will be followed up in 2024.