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Although linseed oil (LO) has been used in wood protection for centuries, research continues to develop new and more effective formulations and treatment approaches. In the future, growing interest in LO use could be expected due to its cost and environmental friendliness. This review summarizes recent research (from 2000 onwards) on the use of LO in wood protection, published in peer-reviewed scientific journals and included in the online publication databases Scopus or Web of Science. The studies cover surface and impregnation treatments of various wood substrates using different LO formulations, including chemically modified LO and the use of LO as a base for the development of biofinish and as a medium for thermal modification of wood, as well as research into the mechanisms behind the changes in wood properties due to treatment methods and interaction with LO formulations. Although the improvement of wood hydrophobicity and biodurability dominates, other aspects such as weathering and color stability, adhesion, and environmental safety are included in these studies. In general, almost all of the studies show a greater or lesser potency of the proposed approaches to provide benefits in wood protection; however, the level of innovation and practical feasibility varies.

This research addresses the issue of the heritage preventive conservation in the perspective of energy sustainability, for contributing to the achievement of the Sustainable Development Goals (SDGs) and towards the EU Green Deal. The study analyses and compares four cases associated with different microclimate thresholds as suggested by the standard EN 16893:2018 (Cases 1–3) and as derived from the outputs of three degradation models for preserving paper, wood, and canvas paintings (Case 4). Weather-based indices (degree and gram days) were calculated to estimate trends in the potential energy demand of collection facilities in three European cities belonging to different Köppen-Geiger climate zones (Cfb, Csa, and Dfb), under recent past (1981–2010) and near/far future climate scenarios (2021–2050 and 2071–2100) from two Shared Socioeconomic Pathways (SSP2-4.5 and SSP5-8.5). The findings suggest that adapting facilities’ management strategies to focus on collections preservation can facilitate the achievement of 5 out of 17 SDGs, offering a viable alternative to costly energy retrofits and encouraging the development of shared solutions for similar facilities in the same climate zone. The results can contribute to inform the revision of EN 16893 and to face major challenges such as the preservation of paper collections in southern latitudes.

The wood photodegradation, including discolouration caused by exposure to UV and solar radiation, has been intensively studied, while the effect of artificial lighting on wood has been little investigated. In the present study, the effect of three types of artificial light sources (LED, incandescent, and fluorescent lamps) on the colour changes of wood was evaluated. LEDs with high (6500 K) and low (3000 K) correlated colour temperature were employed in the experiments. Wood colour was assessed by spectrophotometric measurements of reflectance spectra, which were converted into colour parameters of the CIELAB colour system. The total discolouration as well as the changes in colour lightness, chroma (saturation), and hue were evaluated for two hardwood species (birch, oak) and two softwood species (spruce, pine - sapwood and heartwood) depending on the irradiation dose. Visually perceivable changes in colour of all woods were observed already at relatively low irradiation doses, indicating a high sensitivity of the wood to radiation emitted by artificial light sources. Comparing the softwoods and hardwoods included in the study, the latter proved to be more resistant to discolouration caused by the tested light sources. Overall, greater colour changes in long-term exposure were caused by incandescent and fluorescent lamps, although more rapid discolouration developed in the early stage irradiation with LEDs. A substantial difference between the effect of the tested LEDs was only observed in the initial phase, when the cool LED (6500 K) caused more discolouration. The changes in the colour parameters were complex and varying in directions, including a reversal with the accumulation of the irradiation dose, indicating that the exposure to artificial light sources resulted in continuous alteration in the shade of the wood colour.

Effective prevention of mould growth indoors is still an important topic considering that mould growth is frequently observed in buildings, it causes serious health hazards and can irreversibly damage infected objects. Several studies have been conducted and mould growth models developed. Despite that, some potentially important aspects such as water damage and spore contamination have received only little attention. The objective of the present study was to investigate the effect of the initial moisture content of wood and spore contamination on mould development indoors. The mould tests were performed in constant temperature (10, 20 and 30 °C) and relative humidity (91% and 97%) conditions. The results show that wetting of wood specimens prior to the test significantly accelerates mould growth at a temperature of 10 °C. For the other temperatures, the effect was insignificant. Similar results were obtained for the test involving dry (conditioned at RH 50%) and conditioned specimens (RH 91% or RH 97%). The results regarding initial spore contamination show that significantly longer periods are required for mould to develop without spore contamination at 10 °C and 20 °C, while at 30 °C the effect is relatively small.

Most microplastics (MPs) are generated as a result of photodegradation during the life of plastic products and after the end-of-life as mismanaged waste. At present, it is impossible to avoid plastic-based materials altogether because of their unique properties, versatility, and price. An option is to set limits on how much MPs these materials can release over their lifetime, which would not only reduce MPs pollution, but also improve product quality. However, there is a lack of reliable methodologies for assessing the generation of MPs from these products during use or when they are left as unmanaged waste. The objective of this study was to develop a novel method to assess (collect and quantify) MPs formation from plastic-based materials during weathering. The developed process design is based on a well-established accelerated weathering tester that has been modified by incorporation of a sieve system and water recirculation. The case study is carried out on a recycled polypropylene (rPP) and wood plastic composite (WPC) made from wood particles and the same rPP. Despite the lower plastic content, WPC released significantly more MPs (up to 9.4 g/m 2 ) than the rPP (up to 0.3 g/m 2 ) in the same weathering conditions and duration. Examination of the degraded surfaces revealed that the wood particles facilitated the release of MPs most likely due to moisture fluctuations causing wood swelling induced internal stresses. The collected MPs were mainly below 500 μm and their properties were different comparing to MPs made by cryogenic milling. PY-GC-MS did not detect MPs smaller than 20 μm that could pass through the smallest sieve and end up in the effluent. The reproducibility of the measured MPs release using the process design was very good during the tested weathering period, with variations of less than 7%.

As a vast majority of glued wood products are intended for outdoor use or for building construction, impregnation with different agents is important for ensuring proper performance. It has been shown that the impregnation prior to gluing has several disadvantages, therefore the possibility of carrying out impregnation after gluing is analysed in the present research. Impregnation efficiency as well as the effect on the bond quality is evaluated for the one-component polyurethane glued wood specimens. The results showed that the impregnation with Cu preservative after gluing did not affect the shear strength of the glued wood specimens, but did significantly restrict Cu preservative penetration due to the adhesive bondlines. Considering the results, the possibility of improving the impregnation efficiency was also investigated. By using specific adhesive application designs, which cover the bondline only partially, it was possible to improve the impregnation efficiency. However, the Cu distribution was inhomogeneous and the improvement was noticeable only up to the second bondline. The partial adhesive application design also affected the bond strength of glued wood specimens, which resulted in a decrease both in dry and wet state. However, the reduction was not so sever as to cause delamination during three consecutive wetting and drying cycles.

Life cycle assessment is a valuable tool for evaluating the environmental performance of different products and services. According to the European Commission, forests are indispensable and the most effective strategy for climate change mitigation, although raw wood products (roundwood, pulpwood and fuelwood) are not carbon neutral as previously thought because of the human activities during forest management processes. Apart from climate change, the production of raw wood products also contribute to other environmental impact categories. Previous studies have shown that the life cycle inventory (LCI) data for raw wood products should be collected from the site-specific not from more generic sources because of the significant differences in several geography- and technology-dependent factors. However, less discussed are time-dependent factors, which should also be acknowledged especially because of the long growing time of trees. By analysis of the forest management history, the main objective of the presented study was to determine which forest management activities were performed during the growth phase of currently harvested birch ( Betula spp.) roundwood in Latvia and, based on these results compile the LCI. The results of the forest management history analysis showed that for currently produced birch roundwood only logging operations should be considered in the LCI. Subsystems such as seed production, seedling production and silvicultural operations were not practiced or had only minor impact due to low mechanization level in the past. By taking into account the time-dependent factors (forest management practice, technology, legislation and composition of used chemicals), the LCI was developed and can be used in further calculations of environmental impacts for different wood-based products that are manufactured from currently harvested birch roundwood in Latvia.

Thermal modification of wood has gained its niche in the production of materials that are mainly used for outdoor applications, where the stability of aesthetic appearances is very important. In the present research, spectral sensitivity to discoloration of thermally modified (TM) aspen wood was assessed and, based on these results, the possibility to delay discoloration due to weathering by non-film forming coating containing transparent iron oxides in the formulation was studied. The effect of including organic light stabilizers (UVA and HALS) in coatings as well as pretreatment with lignin stabilizer (HALS) was evaluated. Artificial and outdoor weathering was used for testing the efficiency of different coating formulations on TM wood discoloration. For color measurements and discoloration assessment, the CIELAB color model was used. Significant differences between the spectral sensitivity of unmodified and TM wood was observed by implying that different strategies could be effective for their photostabilization. From the studied concepts, the inclusion of the transparent red iron oxide into the base formulation of the non-film forming coating was found to be the most effective approach for enhancing TM wood photostability against discoloration due to weathering.

Large research work is currently being performed concerning different elaborated new wood protection methods. However, combining industrially well-approbated processes is also considered potentially quite promising and such approach is being actively studied. The objective of the present study was to investigate peculiarities of interaction between liquids and thermally modified (TM) birch wood ( Betula spp.). This knowledge is essential for proper TM wood post-treatments involving its impregnation as well as for evaluation of potential wood moisture dynamics in outdoor applications. Changes caused by TM (150–170 °C) in a closed system under elevated pressure in wood wettability, permeability, liquid absorption capacity, and drying characteristics were evaluated. The results concerning absorption capacity, which is mainly related to wood anatomical features and is density-dependent, indicated reduced absorption capacity of TM wood compared with unmodified birch of similar density. Permeability, which characterises the ease with which liquid is transported through a wood porous system, was evaluated by capillary absorption tests through the samples’ tangential and radial surfaces. TM made birch wood less permeable through both surfaces as well as less anisotropic regarding transverse absorption rates. Moreover, TM also caused a decrease in drying rates for birch wood impregnated with water. Reduction in permeability influences the impregnation process of boards and no full saturation was detected for TM boards when applying an impregnation schedule providing complete saturation for unmodified boards. On the other hand, less water was absorbed by TM boards exposed to rain on outdoor weathering racks.

Considering interior applications, sunlight, both direct through open window and through window glass, and artificial lighting are the main sources of radiation possessing sufficient energy to trigger photodegradation processes in wood. LED lamps, which emit mostly visible light, are becoming the dominant artificial light source in various interiors. In the present study, photodegradation of thermally modified (TM) and unmodified (UM) ash (Fraxinus excelsior), aspen (Populus tremula), and pine (Pinus sylvestris) due to exposure to UV radiation and LED lamps was evaluated and compared by analysing wood discolouration (CIELAB colour space), changes in reflectance and FTIR spectra, and formation of water-soluble components. The results show that, apart from UV radiation, LED lamps may cause considerable photodegradation of both TM and UM wood resulting in visually perceptible colour change, alteration in chemical structure and formation of water-soluble components. Improved photo-stability was observed for TM wood exposed to UV radiation, while even more changes in FTIR spectra were detected for TM than UM wood in the experiment with LED lamps. Comparing TM and UM wood, the changes due to photodegradation were quite similar for TM wood of all species while significant differences were observed in the case of UM wood.