Experts from the Faculty of Forestry and Wood Technology at Mendel University in Brno (FFWT MENDELU), specifically from the Department of Wood Science and Wood Technology, are seeking ways to replace exotic timber used in urban furniture with local wood species such as beech and ash. By means of chemical modification, they are increasing the wood’s resistance to weather conditions and pests while also improving its dimensional stability. Thanks to this modification, locally sourced wood could be used in the production of urban furniture, including not only benches, but also litter bins and public transport shelters. The researchers are collaborating on the innovative project with mmcité company.
Within the product portfolio of mmcité, jatoba — an extremely hard wood originating from Brazil — is most commonly used for urban furniture production. It possesses ideal properties, being resistant to fungal decay and maintaining its quality over time. The aim of the research is to find a local alternative with a significantly lower environmental footprint. The FFWT MENDELU experts are focusing primarily on beech, which is abundant in the Czech environment and commonly used indoors. However, in outdoor conditions it tends to degrade, making modification necessary to ensure the wood retains stable properties.
“The key lies in the process of gaseous acetylation. This technology uses an organic compound based on acetic acid, through which we alter the wood’s cellular structure by substituting hydroxyl groups with acetyl groups. The result is a material that resists wood-destroying fungi, does not crack or warp, and remains stable even under the most demanding conditions without requiring additional maintenance. Over time, the wood surface naturally develops a grey patina outdoors, while internally the material remains strong and stable. The method can also be applied to other wood species, such as ash,” explained Jakub Dömény from the Department of Wood Science and Wood Technology at FFWT MENDELU.
The researchers initially tested the chemical modification on small laboratory samples before moving to a pilot scale using samples approximately seventy centimetres long. For the modification of real structural elements, they now have a specially designed device at the Josef Ressel Research Centre capable of accommodating solid wood pieces up to two metres in length. “Thanks to the application in the gaseous phase, the process is more cost-effective because it requires a smaller amount of the modifying substance. For larger pieces, we use pressure of around 9 bar to ensure deeper penetration of the substance into the wood structure, thereby modifying the element throughout its entire cross-section,” Dömény added.
The properties achieved in the modified wood were then directly verified in the research centre. “Resistance to changes in environmental humidity was tested in a climate chamber, with the main indicators being changes in the weight and dimensions of the wood samples. Using an artificial weathering chamber, we simulated outdoor conditions, including the effects of rain, temperature fluctuations, and UV radiation. This confirmed that chemically modified wood neither cracks nor deforms, over time it merely lightens and turns grey, which also occurs with exotic timber. A crucial part of the research was testing resistance to wood-destroying fungi. It turned out that while untreated wood loses a significant proportion of its mass through degradation, chemically modified wood is practically unaffected by fungi,” the researcher stated.
In addition to beech and ash, the FFWT MENDELU researchers also experimented with modifying spruce and birch, the latter of which is expected to remain resilient even under future climate change conditions. An especially interesting option is the testing of acetylated balsa wood for use in space applications. “It is a sustainable material that is extremely lightweight, offers a favourable strength-to-weight ratio, and, as a natural renewable resource, represents a more environmentally friendly alternative which may leave behind fewer harmful residues during satellite disintegration in the atmosphere than conventional metallic structural materials,” Dömény explained.
The aim of the project was to create a prototype of outdoor seating furniture incorporating a solid wood component made from chemically treated timber. The knowledge gained may in future contribute to assessing the economic and environmental benefits of introducing the production of modified wood species for urban furniture manufacturing. The project is co-financed by the European Union.
Contact for further information: Ing. Jakub Dömény, Ph.D., +420 545 134 550, jakub.domeny@mendelu.cz, Department of Wood Science and Wood Technology, FFWT MENDELU