More fresh wood for sawmills by implementing trait-based cutting in the forest
The focus of this project has been to investigate whether the proportion of fresh twig timber can be increased from the forests in Norrbotten by using a function that describes where in the stems the twigs become healthy. The function is available in many of today's harvester computers and by activating it, so-called automatic fresh twig detection can be done.
Three harvests have been followed from forest to finished product. A total of 3500 logs were decomposed into 7000 planks and analyzed. The results from the harvests indicate that the harvest of freshly cut logs can be increased and that a suitable ratio between the diameter where the sawdust is freshly cut and the diameter of the pine trees at breast height is 0.84 for mature stands in the catchment area of Seskarö Sawmill. With this ratio, 80% of the fresh-cut logs also became fresh-cut products in the adjuster.
The high ratio means that only the root log is classified as either black spruce or free spruce, while the other log types always become free spruce. If the rootstocks are isolated in the analysis, the success rate drops to 53%. The size of the quota is also linked to how the individual sawmill defines its fresh twig products and cannot be seen as general for all sawmills. Algorithm development has also been an integral part of the project. It has been based on X-ray and 3D parameters for a total of 360 variables from 1650 logs and 3300 sorting results from the adjuster.
Only logs where both planks could be matched to the original log with high reliability have been analyzed. It can be concluded that the current fresh-cut model is significantly worse at assessing root logs than top and middle logs.
The project has shown that dividing the logs into root logs and top/middle logs, and then using separate prediction models for each log type, better identifies fresh-cut logs than the current algorithm. The new algorithm captures approximately 15% more freshly cut logs than the previous model. Through harvesting simulations, figures have been produced that show how the total timber outcome in the deliveries to Seskarö is affected if automatic free-twig harvesting is applied and the relative value of free-twig logs is increased. A relative increase in the value of free-twig logs by 5% resulted in the volume of free-twig logs increasing from 12 to 20%, while black-twig logs decreased from 24 to 17%. At the same time, the average length of fresh twig logs increased by 21 cm, while the average length of other timber assortments remained virtually unchanged.
The conclusion of this project is that there seem to be conditions for an increased production in Norrbotten of the fresh-twig sawmill products, which is a segment with good sales on the market.
Area: Materials & Processes
Budget: SEK 354,000
March 2021 - June 2022
Project leader: Ann Eklund, Sveaskog
Funding: This project is funded by TCN.
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