Mittuniversitetet

Caffeine-treated wood is valued for its decay resistance, but caffeine high leachability under outdoor conditions significantly reduces its long-term effectiveness. This study aimed to mitigate the leachability of caffeine-impregnated Scots pine wood by incorporating either formaldehyde or glutaraldehyde. The treatments were evaluated using standard leachability analysis (EN 84), decay resistance testing (EN 113), mass spectrometry, attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, and mechanical testing. Leaching tests revealed that caffeine-glutaraldehyde-impregnated wood exhibited the lowest mass loss after leaching (3.30 ± 0.15%), outperforming caffeine-treated (6.18 ± 0.15%) and caffeine-formaldehyde-treated (5.94 ± 0.13%) specimens, indicating superior caffeine fixation. ATR-FTIR spectroscopy showed that characteristic caffeine bands diminished following leaching, confirming caffeine leachability. However, caffeine-glutaraldehyde-treated samples exhibited less pronounced spectral changes compared to caffeine-formaldehyde-treated samples. Mass spectrometry further corroborated these findings, detecting higher caffeine content in glutaraldehyde-treated wood than in caffeine-only specimens after leaching test. Decay resistance tests demonstrated that caffeine-glutaraldehyde-treated wood retained high resistance to fungal decay both before and after leaching. Mechanical tests revealed that the modulus of rupture (MOR) was preserved post-leaching only in caffeine-glutaraldehyde-treated samples. These findings highlight the effectiveness of low concentrations of glutaraldehyde in reducing caffeine leachability, thereby enhancing the decay resistance and durability of treated wood, making it a promising approach for outdoor applications. 

The basic density and shrinkage properties of Scots pine wood from commercial first and second thinning-stage forests were studied in eastern Finland with a reference from final-felling forests. Linear mixed model analysis was applied, indicating statistically significant differences in basic density between stand types and forest site types, with significant effects of cambial age and height position. Additionally, the 2-level interaction terms between site type, cambial age and height position were significant. In Myrtillus type sites, the basic density was 380 kg/m3 for first-thinning wood, and 407 kg/m3 and 406 kg/m3 for second-thinning and final-felling wood, respectively. Young thinning trees showed, on average, wider growth rings (2.83 mm) compared to mature trees (2.04 mm). Density and latewood proportions increased with tree age, particularly in poor site types, whereas the growth ring width had opposite effects. Significant differences were observed in radial, tangential and volumetric shrinkage across stand types, height positions and radial positions, while the longitudinal shrinkage model indicated statistically significant differences between radial positions only. The radial shrinkage was 4.04% in the first thinnings and 4.44% in the second thinnings, while the tangential shrinkage was 6.98% and 7.16%, respectively. The substantial variation in properties, particularly in the first thinnings, likely reflected the presence of juvenile wood, stem form defects and reaction wood in the harvested material, making it less suitable for mechanical processing. The results confirmed that the properties of second-thinning wood enable its use in applications requiring higher density and allowing reasonable shrinkage.

Climate change, energy consumption, and carbon footprint goals pose challenges for the hygrothermal performance of Nordic building structures. Residential buildings in Finland, designed to last up to 100 years, must perform well under not only the current but also future climate conditions. Realized carbon emissions align with the RCP8.5 scenario predict a temperature rise of over 4 °C by 2100, resulting also in much higher moisture loads for buildings. This study validated numerical models with data from five insulation assemblies to assess their hygrothermal performance and mould growth under future climate conditions. Measurements conducted in a climate cabin over a 70-day period showed strong alignment with simulations. Using Finnish Moisture Design Years (MDYs) for various future climate scenarios, we found the critical point at the exterior side of the interior sheeting gypsum board. Mineral wool insulation inside the vapour barrier performed poorly under increased humidity, while organic insulations showed markedly better performance. Mould growth on tested organic insulations was predicted only in the RCP8.5 2080 scenario. Based on the studied options, optimal structures may combine linen or wood fibre inside and mineral wool outside the vapour barrier, with gypsum board having higher water vapour resistance to mitigate indoor humidity effects. 

Geopolymers have elicited significant attention in the field of construction and building materials due to their enhanced durability, physical load-bearing ability and chemical resistance. This study investigates the effects of geopolymer impregnation on wood, together with commercial tannin-rich bark extract Colatan GT10, which, by itself, preserves wood against decay but leaches out once the wood is exposed to water. The efficacy of the treatments is evaluated through attenuated total reflectance Fourier transform infrared (ATR FTIR) spectroscopy, mechanical testing, decay resistance assessment (EN 113) and leachability analysis (EN 84). The results showed that the two-step tannin-geopolymer impregnation improved the durability of wood against wood decay fungi. The mechanical properties of the treated wood specimen were not different from that of the untreated controls, and the performance of the treated wood specimen was retained after the leaching test. The FTIR revealed that the absorbance of tannin at 10 and 5% treatments was reduced after leaching, indicating the leachability of tannin. The combination of tannin at 5% with subsequent geopolymer at 4% treatment yielded the best performance, showing no significant change in absorbance before and after the leaching test. Overall, this study highlights the potential of combining tannin and geopolymer impregnation treatments to enhance the performance of wood in terms of fixation, leachability and wood decay resistance. These findings contribute to the development of a durable wood material for various applications, such as outdoor construction, where resistance to decay is a critical factor. 

This study explores tannin and caffeine, natural compounds with inherent antifungal properties, as scalable treatments to enhance the physical and mechanical performance of oriented strand board (OSB). Unlike previous research that primarily focused on durability, this work evaluates the effects of these bio-based treatments on leaching resistance, internal bond strength (IB), bending properties, water absorption, thickness swelling, and vertical density profile (VDP). The results demonstrate significant improvements over commercially available OSB, particularly in mechanical performance. Post-leaching, both treatments exhibited superior IB, with tannin-treated panels achieving the highest IB value (0.27 MPa). The bending analysis revealed that caffeine-treated panels that were not subjected to leaching achieved the highest modulus of rupture (MOR, 62.54 MPa) and modulus of elasticity (MOE, 10.36 GPa). Both treatments retained significantly higher MOR and MOE values post-leaching compared to the industrial reference and untreated panels. Water absorption and thickness swelling were comparable among tannin-treated, caffeine-treated, and untreated panels but were significantly lower than those of the industrial reference, which was included for general benchmarking purposes alongside the laboratory-made control. VDP analysis showed caffeine-treated panels had the lowest density prior to leaching, whereas tannin-treated panels maintained the highest density after leaching. These findings highlight tannin and caffeine as effective and scalable treatments, providing a sustainable alternative as functional additives for industrial engineered wood product manufacturing.

Coffee roasting by-products represent a significant, underutilized side-stream globally. This study investigates hydrothermal liquefaction (HTL) as a method to convert these materials into hydrochar, water-rich light oil, and heavy oil. Using HTL at 300 degrees C for 60 min, we evaluated the energy content and properties of the resulting hydrochars, finding energy values exceeding 33 MJ/kg-significantly higher than the 19-21 MJ/kg of the raw materials. Hydrothermal liquefaction of spent coffee grounds produced more hydrochar (18 g) and heavy oil (1.2 g) than silverskin (12-14 g hydrochar and 0.1-0.5 g heavy oil). In contrast, silverskin generated twice as much light oil (9.7 g) as spent coffee grounds (4.6 g). Silverskin hydrochars exhibited higher gross calorific value (Baqu & eacute; 33.95 +/- 0.06 MJ/kg, Mariposa 33.86 +/- 0.07 MJ/kg, Meira 33.22 +/- 0.00 MJ/kg), lower ash content (3-5%), and reduced volatile matter (57-61%) than their raw form. Spent coffee grounds produced hydrochar with the highest gross calorific value (34.27 +/- 0.01 MJ/kg), lowest ash content (0.8%) and the most significant reduction in volatile matter. Light and heavy oils produced were rich in alkaloids, fatty acids, and phenolic compounds, with potential applications in cosmetics and pharmaceuticals. This work contributes to both bioenergy production and circular economy strategies, valorising the two main side-streams of the coffee industry. With broad implications for sustainable waste management, this study highlights the potential of HTL to advance global bioenergy goals.

This work aims to modify wood using dilute geopolymer suspensions for improving its decay resistance, leachability, mechanical properties and fire resistance. Scots pine (Pinus sylvestris) sapwood specimens were impregnated with either 1, 3 and 5% geopolymer suspensions. The 3% and 5% geopolymer treated wood specimens presented lower mass loss caused by the decay fungus Coniophora puteana than control specimens, while 1% treatment increased the mass loss significantly. The geopolymer suspensions did not affect the mechanical properties of the sapwood specimens. The pine sapwood treated with geopolymer and subjected to leaching displayed the same mass loss to that of the control specimens exposed to leaching. This suggests that the dilute geopolymer suspension leached out from the wood. The geopolymer-suspension-impregnated wood presented an increased time to ignition compared to controls in the fire resistance test, but also a higher amount of smoke released. Results indicate that modification of wood using dilute geopolymer suspension is promising, but presents drawbacks that need to be addressed, such as leaching.

Viruses may persist on solid surfaces for long periods, which may contribute to indirect transmission. Thus, it is imperative to develop functionalized surfaces that will lower the infectious viral load in everyday life. Here, we have tested a plastic surface functionalized with tall oil rosin against the seasonal human coronavirus OC43 as well as severe acute respiratory syndrome coronavirus 2. All tested non-functionalized plastic surfaces showed virus persistence up to 48 h. In contrast, the functionalized plastic showed good antiviral action already within 15 min of contact and excellent efficacy after 30 min over 90% humidity. Excellent antiviral effects were also observed at lower humidities of 20% and 40%. Despite the hydrophilic nature of the functionalized plastic, viruses did not adhere strongly to it. According to helium ion microscopy, viruses appeared flatter on the rosin-functionalized surface, but after flushing away from the rosin-functionalized surface, they showed no apparent structural changes when imaged by transmission electron microscopy of cryogenic or negatively stained specimens or by atomic force microscopy. Flushed viruses were able to bind to their host cell surface and enter endosomes, suggesting that the fusion with the endosomal membrane was halted. The eluted rosin from the functionalized surface demonstrated its ability to inactivate viruses, indicating that the antiviral efficacy relied on the active leaching of the antiviral substances, which acted on the viruses coming into contact. The rosin-functionalized plastic thus serves as a promising candidate as an antiviral surface for enveloped viruses.IMPORTANCEDuring seasonal and viral outbreaks, the implementation of antiviral plastics can serve as a proactive strategy to limit the spread of viruses from contaminated surfaces, complementing existing hygiene practices. In this study, we show the efficacy of a rosin-functionalized plastic surface that kills the viral infectivity of human coronaviruses within 15 min of contact time, irrespective of the humidity levels. In contrast, non-functionalized plastic surfaces retain viral infectivity for an extended period of up to 48 h. The transient attachment on the surface or the leached active components do not cause major structural changes in the virus or prevent receptor binding; instead, they effectively block viral infection at the endosomal stage. During seasonal and viral outbreaks, the implementation of antiviral plastics can serve as a proactive strategy to limit the spread of viruses from contaminated surfaces, complementing existing hygiene practices. In this study, we show the efficacy of a rosin-functionalized plastic surface that kills the viral infectivity of human coronaviruses within 15 min of contact time, irrespective of the humidity levels. In contrast, non-functionalized plastic surfaces retain viral infectivity for an extended period of up to 48 h. The transient attachment on the surface or the leached active components do not cause major structural changes in the virus or prevent receptor binding; instead, they effectively block viral infection at the endosomal stage.

This study aimed to investigate the potential of converting bio-based residues from industrial production of mushrooms and tomatoes into more valuable chemicals with antifungal properties using hydrothermal liquefaction (HTL). Liquid fractions were obtained from HTL of spent substrate of Agaricus bisporus (Lange) Imbach and Pleurotus ostreatus (jacq.) P. kumm., recomposted Agaricus bisporus spent substrate, and tomato residues. The quantitative 1H NMR spectroscopy analysis revealed that the HTL liquids of all residues contained antifungal constituents like phenols and organic acids. The HTL liquids at dilutions of 10 % were able to inhibit the fungi by over 80 %. Interestingly, the fungus P. ostreatus showed tolerance to these constituents as its growth was promoted at the lowest concentration of all the HTL liquids. The HTL liquids had lower ecotoxicity than the commercial wood preservative. These results suggest that the tested residues could be a promising source of preservative chemical constituents for the wood industry. 

Wood chips and sawdust are used for cultivating Ganoderma lucidum mushrooms. In Northern Europe, side-streams of Pinus sylvestris are highly abundant, however as cultivation substrate they inhibit the growth of G. lucidum. To identify the changes in lignocellulosic composition after fungal degradation, the major lignocellulosic components in P. sylvestris and an optimal substrate for G. lucidum, Populus tremula were analyzed. Populus tremula was evenly degraded while the glucan fraction of P. sylvestris was not degraded and its lignin fraction was consumed almost completely. Despite not being an optimal substrate, P. sylvestris was successfully delignified by G. lucidum.