The disposal of wood waste at facilities for incineration in Sweden is the only applied management practice today. Energy production from biomass has gained attention for its potential to recover energy and reduce greenhouse gas emissions. However, besides being a valuable source for energy generation, wood waste can be effectively recycled into new products. Specifically, recycling wood waste into particleboard is the widely practiced method in Europe, while its benefits have not been explored in the country so far. The objective of this study is to assess the environmental, social, and economic sustainability of producing particleboard and generating energy from wood waste in Sweden. This research investigates four alternative systems for wood waste disposal. The first system involves the production of heat, the second system involves heat and power by wood waste, while the third and the fourth systems, in addition to energy recovery, include partial recycling of wood waste in particleboard production. A life cycle sustainability assessment covering all three pillars (environment, social, and economic) of sustainability was conducted to compare these systems. The results show that adding recycling schemes to incineration in wood waste management practices strengthens the sustainability for all three aspects, and hence, these management methods can be considered as complementary methods rather than competing methods. When all sustainability categories are considered, alternative three (heat recovery and recycling) comes forward as the best option in 11 out of 16 impact categories.

Previous studies have shown that thermally modified wood (TMW) performs well in outdoor, above-ground conditions in terms of resistance to wood-decaying fungi. Yet, little is known about the development of defects such as checks and the corresponding mechanical properties of TMW in this condition. This experiment focused on the effect of 30 months outdoor above-ground exposure (weathering) on the degree of checking, dynamic stiffness and static bending properties of thermally modified timber (TMT) of Norway spruce. Two board pairs per log were cut from 190 logs; one board of each pair was thermally modified and the other used as control. Then, 90 board pairs were exposed to the weather in south Sweden. Surface checking and axial stiffness were monitored at six-month intervals by using digital photography and non-destructive tests (time-of-flight and resonance method) to monitor changes in the material upon weathering. Finally, all boards were tested destructively in a 4-point static bending test following EN 408 standard. Results showed that weathering had no significance influence on static bending properties of TMT even though the degree of checking was considerably higher in TMT than unmodified timber after weathering. In particular, checks along growth rings were deeper, longer and more common in TMT after weathering, especially on the pith side of boards. The maximum depth of these checks did not depend on board orientation (i.e., which side was exposed) and exceeded limits given in strength grading standards for 7% of the modified boards included. Axial dynamic stiffness determined at 6-month intervals was less influenced by fluctuations in moisture content for TMT compared to unmodified timber, but did not confirm the increase in the degree of checking of TMT. The presence of checks from weathering did influence failure modes in TMT; horizontal shear failure became more frequent and some boards failed in compression.

This paper presents electrical resistance characteristics of ThermoWood® Thermo-D Norway spruce for wood moisture content measurements below fibre saturation point. Electrical resistance along the grain of small clear wood specimens was measured at various moisture content levels of ~ 4–15% for thermally modified and ~ 5–25% for unmodified spruce. The results show that—similar to unmodified wood—the relationship between wood moisture content and electrical resistance can be well described by a first order polynomial function obtained from simple linear regression. This provides accurate resistance-based predictions of thermally modified wood moisture content. In addition, established temperature corrections derived previously from unmodified wood seem applicable to thermally modified wood.

Acoustic emission (AE) measurements were used to detect the onset of crack initiation and propagation, as well as to monitor crack front advancement during fracture resistance tests on wood-adhesive bonds. In parallel, digital image correlation (DIC) was employed as an independent technique to also monitor crack front progression. These measurements were conducted with the aim of further adapting and developing the J-integral approach for fracture characterisation of wood and wood-adhesive joints. In this method, double cantilever beam (DCB) specimens are loaded under pure bending moments to determine R-curves and cohesive laws. Tests were performed on European beech wood specimens bonded with a bio-based wood-lignin adhesive. The results show that AE can effectively identify the onset of crack initiation and propagation, supporting the characterisation and interpretation of R-curve and cohesive law data. Additionally, both AE-based localisation and DIC-derived strain fields can be used to estimate the cohesive zone length during crack growth.