Intense competition for raw materials gives an advantage to those who value it most

As a result of the Green Deal and climate neutrality goals, the demand for wood in the production of energy, biofuels, construction, packaging and chemicals has increased. This has almost doubled the price of wood as a raw material in recent years, and the intense competition for raw materials gives an advantage to those who value wood the most. Jaan Kers, professor of wood technology at TalTech, talks in more detail.

The article first appeared in the December 2021 journal All about industrial engineering

"Today, we have to think about using materials exactly as much as we need and where we need them. We need to consider how wood can be used in cascade or replaced by other biocomposite materials based on natural fibers such as reed or hemp fiber. Low-quality wood species could also be used instead of birch wood in the production of veneer and plywood, and very carbon-intensive materials such as metal and concrete could be replaced with natural materials," Kers gives several examples. "Perhaps, as the architect Alex de Rijike has said: 'Wood is a material of the 21st century, just as concrete was a material of the 20th and steel was a material of the 19th.'"

Reinforced concrete wall and ceiling panels, which have triumphed for decades, are now being successfully replaced by cross-laminated wooden panels, and the structure is strengthened by beams and posts made of glulam, steel can be replaced by high-strength densely pressed wood. Polymers can be produced from the cellulose and lignin separated by the chemical fractionation of wood, which replace consumer plastics and wood glues from fossil raw materials. Acetate and viscose fibers can be produced from cellulose. Carbon fiber and high-strength composites can be produced from lignin. At the same time, wooden and plywood jigs are needed to build every concrete building.

According to Kers, when thinking about the green deal in the field of construction, they try to direct materials to cascade use. For this purpose, the wooden structures must be designed to be disassembled, and the separated roof structure, wooden walls and wooden panels must be adapted to be reusable. Biodamage-free wood from the demolition of log houses can be used multiple times because the logs are easily numbered for disassembly and reassembly. If the metal fasteners are removed from the log, it can be made into lumber and solid wood furniture. In this way, we gain multiple uses for wood, either at the same level of the cascade in the construction of buildings or a level below, for example, as non-structural wood in interior finishing or furniture production.

Modern wooden buildings can be designed in such a way that the roof is assembled separately and lifted onto the building with a crane, and the walls of the house can be dismantled or sawn open if necessary. Since the walls and ceiling and floor panels with a wooden truss structure or cross-laminated wooden panel are produced as separate modules in a wooden house factory, in order to disassemble them, the mechanical fastening systems on the floor and ceiling structures and the walls must be changed, so that the modules can be easily separated from each other when the building is demolished and used during the construction of the next building. Kers brings, for example, the Red Bull formula team's three-story 1200 m² demountable office building made of cross-laminated timber, which is erected with the help of 2 cranes, 2 forklifts and 25 workers in 32 hours for each stage at a new location.

The construction wood that was used in the buildings is used in the production of designer furniture, and the wood of the old furniture is used in the next step of the cascade, chopped, for example, in the production of chipboards. The last stage of wood recycling is energy use or biodegradation, and the CO2 released during this process is re-bound by the trees of the growing forest. One example of the last stage of the cascading use of wood is the construction of hiking trails in bogs, where newer wood is placed on top of the old boardwalk and the base layer is left to rot in the swamp.

| Diagram of the cascading use of wood

Wood is a material with a long history, but very new

Modern insulation materials are a big problem, because their production takes a certain amount of energy, which is why options with a smaller footprint are constantly being sought. After all, there is also cellulosic wool based on the circular economy, which needs to be impregnated with fire retardants. According to Kers, the Austrians built a multi-storey office building in Hallein with 23.4 cm thick walls of TimberBrain cross-laminated timber to achieve the energy savings typical of a passive house without the need for additional thermal insulation. In Turku, Finland, two apartment buildings were built at the same time, which are identical in architecture, but with one difference: one house was built of wood, the other of concrete, the purpose of which is to compare the environmental impact.

"Wood is a building material with a long history, but its endless possibilities of use are being explored very actively today as a result of the green revolution. Wood can be chemically modified by adding polymers to make it resistant to external environmental conditions and similar in strength to metal. Wood can be friction welded, but gluing is more common, which in turn has become another important area of development - to make natural soy-based bioglues to reduce easily volatile dangerous compounds," says Kers.

As one of the innovative solutions, the professor highlights cross-laminated wooden panels, which were developed in Austria and Germany in the 1990s. It is made of finger-jointed material with alternating cross-glued layers of wood, as a result of which the load bearing capacity of the panel is ensured in two directions. The length of the panels can be as much as 15-16 m and the width 3.5 m, they can already be milled in the factory for communications and simply assembled as modules on the construction site. Due to their construction, the panels are very stable and strong, and remain stable even in case of changes in humidity. They could replace concrete and be an environmentally friendly solution in construction. However, plywood has been used, for example, as a protective material against space radiation in the body of the Finns' WISA plywood satellite, which is protected from reacting with oxygen by a nano-surface coating.

| TalTech researchers: from left Percy Alalo, Maria Kulp, Tiit Lukk, Heikko Kallakas and Jaan Kers visiting Innorenew in Slovenia

Bad news: the bark beetle has done its job in the coniferous forests of Europe

"Unfortunately, Europe's wood resources have suffered a lot everywhere, because the bark beetle has done its job and dried up a very large number of conifer forests in Central Europe in recent years. Currently, the forests of Germany, France and the Czech Republic have been mainly under attack, but unfortunately bark beetles are no longer an unfamiliar sight in Latvia and Estonia. We do have 251 TP3T of forests under protection, but since diseased trees are not cut down from there, the gorse tends to spread further into commercial forests," says Kers. "Therefore, the availability of material is an increasing concern, and the economical and cascading use of wood is increasingly on the agenda."

At the same time, it is not always necessary to use spruce and pine wood in construction or furniture production. Aspen and other less popular trees could be used just as successfully. "Estonia is at the forefront of the wooden house construction sector in Europe, they are good and innovative. But with all this, we should think about how to use wood in a long-term way to store carbon, and better calculate the life cycle of each product," says Kers.

Both private individuals and businesses are also monitoring the maintenance costs of buildings more than before, which are being tried to be reduced with the help of cutting-edge technology and smart technical systems. For example, they try to make use of the heat directed to the sewers, solar panels and use smart materials. At the forefront of the latter is wood, which stores carbon, is natural, stores moisture and gives it out when heating the room, and makes the indoor climate of the room more pleasant and better.

| Wooden roof structure of a private house