Towards a low-carbon future with pine sawn timber
A 30-tonne sea container is made to seem light as a harbour crane grabs its edges. A new batch of pine sawn timber is ready to be shipped at the Port of Rauma. Construction consumes more materials and energy than any other industry. However, the carbon footprint of the built environment can be lowered with ecologically sustainable materials. Nordic pine is a regenerative raw material. In terms of resource efficiency, the process of refining logs into sawn timber has been perfected. By-products from sawing – such as sawdust, bark and wood chips – are refined into new products, meaning no waste is created. VTT Technical Research Centre of Finland has estimated that more carbon dioxide is absorbed from the atmosphere during the growth of wood used in building products than is emitted during the manufacturing of the product.2 From this point of view, each bundle of sawn timber loaded onto the cargo ship is part of a low-carbon future.
Nordic pine plays an important role in creating a fossil-free future.
A new generation of pines is already growing
also the amount of branchless sawn timber that can be achieved. On average improved pines grow 20 per cent faster than other pines. Even the climate benefits from the improved growth, as improved trees absorb more carbon dioxide from the atmosphere. The breeding work to improve the growth speed, the quality and durability of pine is ongoing. As a result of selective breeding, the profitable genes will concentrate and multiply the benefits in each tree generation.
treatment. A study1 measuring the natural rot resistance of various tree species concluded that heat treatment is most effective in pine heartwood. After heat treatment, the heartwood can be categorised as extremely resistant to decay.
It is May, and Nordic nature is budding. In the regeneration area, shoots of rosebay willowherb and common cow-wheat are pushing their way up, and the first bumblebees are buzzing on the willow flowers. Along with other flowering plant species, they are important sources of nutrition for pollinators. A forestry tractor with a harrow is moving slowly around the regeneration area. The rotating crosscutter discs turn humus away from the mineral soil. Sowing seeds fall into the furrows. Finland’s first Forest Act was issued in 1886. Its foundation was a stipulation decreeing that forests shall not be destroyed. Under the guidance of the Act, the growing stock volume in Finnish forests has increased by over 70 per cent in 50 years3. According to the Finnish Forest Centre, more than 90 per cent of forests are certified. Nordic pine plays an important role in creating a fossil- free future. The seeds germinate quickly in the warming soil. By midsummer, the regeneration area will be covered by saplings. •
The versatility of pine is unparalleled
A harvester grabs the trunk and fells it with one swift move- ment of the chainsaw. A few seconds later, the branches have been cut off and the trunk is cut into logs. As raw material for sawn timber, the versatility of pine is unparalleled. One regeneration-ready trunk can be turned into a branchless butt log, butt logs with few branches, middle logs with dry branches and top logs with fresh branches. Taking into account the various factors – such as quality, dimension, length, moisture content and sawing method – it is possible to produce up to 60 different sawn timber products from one log. The final end uses of sawn timber are determined by the parts of the log. Sawn timber made from butt logs is usually refined into glulam beams and posts for construction projects, where strong and stiff materials are required. Middle logs are used by manufacturers of timber houses and door and window components. The long, regular knot frequency is well suited to the finger joints used in frames and semi-finished products. Top logs with healthy branches are perfect for visually demanding locations. They are refined into internal and external cladding panels and glulam for furniture.
Heartwood extractives protect against decay
Wintry evening darkens quickly, and the temperature drops. In midwinter, temperatures in Finland can fall to minus 30–40 degrees Celsius. For many species winter is a trial, but pines have adapted to it genetically. As the days become shorter at the end of summer, pines stop growing and go through various physiological changes. This process is called cold hardening, and it prepares the pine to withstand temperatures as cold as minus 70 degrees Celsius. In a pine stand ready for regeneration, the tree crowns can reach a height of 30 metres, with their diameter at chest height being around 25 centimetres. Heartwood has formed at the core of the pine. This dense and dark wood is naturally resistant to decay due to its extractives. In mature pines, more than half of the trunk’s volume can be heartwood. Pines’ rot resistance can be further improved with heat
1 Metsä-Kortelainen & Viitanen. 2009. Decay resistance of sapwood and heartwood of untreated and thermally modified Scots pine and Norway spruce compared with some other wood species. Wood Material Science and Engineering. 2 Nykänen et al. 2017. Puurakentaminen Euroopassa LeanWOOD. VTT Technical Research Centre of Finland. 3 Korhonen et al. 2017. Suomen metsät 2009–2013 ja niiden kehitys 1921–2013. Natural Resources Institute Finland (Luke).
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