Temperature-Induced Increase in Methane Release from Peat Bogs: A Mesocosm Experiment

Peat bogs are primarily situated at mid to high latitudes and future climatic change projections indicate that these areas may become increasingly wetter and warmer. Methane emissions from peat bogs are reduced by symbiotic methane oxidizing bacteria (methanotrophs). Higher temperatures and increasing water levels will enhance methane production, but also methane oxidation. To unravel the temperature effect on methane and carbon cycling, a set of mesocosm experiments were executed, where intact peat cores containing actively growing Sphagnum were incubated at 5, 10, 15, 20, and 25°C. After two months of incubation, methane flux measurements indicated that, at increasing temperatures, methanotrophs are not able to fully compensate for the increasing methane production by methanogens. Net methane fluxes showed a strong temperature-dependence, with higher methane fluxes at higher temperatures. After removal of Sphagnum, methane fluxes were higher, increasing with increasing temperature. This indicates that the methanotrophs associated with Sphagnum plants play an important role in limiting the net methane flux from peat. Methanotrophs appear to consume almost all methane transported through diffusion between 5 and 15°C. Still, even though methane consumption increased with increasing temperature, the higher fluxes from the methane producing microbes could not be balanced by methanotrophic activity. The efficiency of the Sphagnum-methanotroph consortium as a filter for methane escape thus decreases with increasing temperature. Whereas 98% of the produced methane is retained at 5°C, this drops to approximately 50% at 25°C. This implies that warming at the mid to high latitudes may be enhanced through increased methane release from peat bogs

Specific Dimensional Change Behavior of Laminated Beech Veneer Lumber (BauBuche) in Terms of Moisture Absorption and Desorption

Replacing greenhouse gas-intensive building materials with wood products from sustainable forestry contributes to the implementation of current climate conventions such as the Paris Agreement. Hardwood products, such as laminated veneer lumber made of beech (e.g., BauBuche), are an alternative to conventional building materials. For the application of wood products in the construction sector, a precise knowledge of the mechanical and physical properties is essential. Therefore, the aim of the present study was to investigate the sorption behavior and associated dimensional changes of the product BauBuche. This was done by applying a manual testing procedure (climatic chamber, balance and caliper) as well as a dynamic vapor sorption analyzer equipped with a camera. During initial moistening after production, due to the irreversible spring back (approximately 2 mm at 50 mm; i.e., 4%), Baubuche shows an extremely strong swelling in the radial direction. Once the maximum spring back is reached, Baubuche shows sorption behavior in the radial and tangential direction, which is comparable to that of solid beech wood in the radial direction. Consequently, the dimensional changes caused by moisture changes must be taken into account in the dimensioning of Baubuche components in order to avoid damage to building structures

Voruntersuchungen zur Integration einer 3D-Spanvermessung in den Spanplattenprozess

Der Einfluss der Spangeometrie, insbesondere der Spandimensionen auf die Eigenschaften von Spanplatten ist bisher nur in Ansätzen erforscht, was in erster Linie auf das Fehlen einer zuverlässigen Methode zur Spanvermessung zurückzuführen ist. Mit der Entwicklung des '3D Particleview' steht Praxis und Forschung seit Anfang 2020 nun ein Laborgerät zur Verfügung, mit dem sich automatisiert die Spanabmessungen sowie die Spanoberfläche und das Spanvolumen umfangreicher Spanproben bestimmen lassen. Die Kernkomponente des Messgerätes ist ein Laser-Profilsensor, der nach dem Prinzip der Lasertriangulation arbeitet. Aufgrund der Neuheit der 3D-Spanvermessung mit Laser-Profilsensoren ist es Ziel dieser Arbeit, Details der Technologie zu erklären und die Ergebnisse von Grundlagenversuchen anhand industrieller Spanfraktionen als Wegweiser für weitere Untersuchungen darzustellen und zu diskutieren. Der Schwerpunkt liegt hierbei auf - der vergleichenden Betrachtung von anzahl- und volumengewichtetem Mittelwert, - dem Einfluss der Montagehöhe des Laser-Profilsensors auf die Messergebnisse, - der experimentellen Untersuchung des nötigen Stichprobenumfangs und - der Dokumentation von Veränderungen der Spandimensionen im Prozess. Weiter wird auf Basis der 'Goldenen Regel der Messtechnik' gezeigt, dass die Auflösung bei der Spanvermessung mindestens 1/10, im 'äußersten Fall' 1/5, der kleinsten erwarteten Abmessung betragen soll. Für die Beurteilung der Plausibilität von Messergebnissen wird die aus Probeneinwaage und dem von der Sensorsoftware ausgegebenen Gesamtvolumen bestimmte Dichte vorgeschlagen. Als plausibel sind hierbei Messwerte anzusehen, bei denen die berechnete Dichte im Bereich der Holzarten liegen, die für die Herstellung der Spanplatte eingesetzt wurden. Sollen für den Plattenaufbau repräsentative Kennwerte bestimmt werden, bietet sich die volumengewichtete Mittelwertbildung an, bei der (gröbere) Späne entsprechend ihres Volumenanteils (stärker) zum Mittelwert der betrachteten Spandimension beitragen. Anhand der vergleichenden Vermessung industrieller Deck- und Mittelschichtfraktionen wird gezeigt, dass die Sensorauflösung bei Standardmontagehöhe für die Vermessung von Deckschichtspänen unzureichend ist und nur für Mittelschichtspäne plausible Werte erfasst werden können. Eine theoretisch erzielbare Auflösungserhöhung durch Verringerung der Montagehöhe des Sensors konnte anhand der Messergebnisse nicht bestätigt werden. Weiter wird am Beispiel einer industriellen Mittelschichtfraktion gezeigt, wie sich experimentell der nötige Stichprobenumfang für eine repräsentative Kennwertbildung bestimmten lässt. Gezeigt wurde auch, dass die Spandimensionen im Prozess ständigen Veränderungen unterliegen, die sich im gezeigten Beispiel (über Tage, Stunden und Minuten) auf ca. ± 10 % belaufen. Basierend auf einer kritischen Diskussion der eigenen Versuchsansätze werden Optimierungsvorschläge für Folgeversuche gegeben.The influence of particle geometry, in particular the particle dimensions, on the properties of particleboard has so far been insufficiently investigated, which is primarily due to the lack of a reliable method for particle measurement. With the development of the "3D Particleview", a laboratory device is now available to practice and research since the beginning of 2020, with which the particle dimensions as well as the particle surface and volume of extensive samples can be determined automatically. The core component of the measuring device is a laser profile sensor that works according to the principle of laser triangulation. Due to the novelty of 3D particle measurement with laser profile sensors, the aim of this work is to explain details of the technology and to present and discuss the results of basic investigations using industrial particle fractions as a guide for further investigations. The focus is on - the comparative analysis of number-weighted and volume-weighted mean values, - the influence of the mounting height of the laser profile sensor on the measurement results, - the experimental investigation of the necessary sample size and - the documentation of variations of the particle dimensions in the process. Based on the "Golden Rule of Metrology" it is shown that the resolution in particle measurement should be at least 1/10, in the "extreme case" 1/5, of the smallest expected dimension. To assess the plausibility of measurement results, the density determined from the sample weight and the total volume output by the sensor software is used. Here, measured values are considered plausible if the calculated density is in the range of the wood species used for the production of particleboard. If representative mean values for the board structure are to be determined, volume-weighted averaging is suitable, in which (coarser) particles contribute (more) to the mean value of the particle dimension under consideration according to their volume share. Based on the comparative measurement of industrial surface and core layer fractions, it is shown that the sensor resolution at standard mounting height is insufficient for the measurement of surface layer particles and that plausible values can only be recorded for core layer particles. A theoretically achievable increase in resolution by reducing the mounting height of the sensor could not be confirmed on the basis of the measurement results. Furthermore, the example of an industrial core layer fraction shows how the necessary sample size for a representative mean value formation can be determined experimentally. It was also shown that the particle dimensions are subject to constant fluctuations in the process, which amount to approx. ± 10 % (over days, hours and minutes) in the example shown. Based on a critical discussion of the own experimental approaches, optimization suggestions for follow-up investigations are given

Limitations of a 3-D Image Analysis-Based Particle Size Measuring System for Wood Particle Dimension Measurement

Against the background of inaccurately measured wood particle dimensions, applying the three-dimensional (3-D) image analysis–based particle size characterization system Partimac 3D XL in pre- liminary tests, metal platelets with various aspect ratios of the three main axes are employed to understand and explain the observed limitations of the measuring principle. It was found that particle width and thickness interact increasingly with a decreasing aspect ratio and, thus, the digital replica and subsequent determination of the dimensions become incorrect. This was ascribed to the random orientation of the particles during image acquisition, which cannot be overcome with a finite number of cameras in the system. 

Effects of formulation variables on surface properties of wood plastic composites

Degree of surface quality of wood plastic composites (WPCs) is a function of both raw material characteristics and the manufacturing variables. The WPC panels comprised of different panel densities (800, 950, 1000, and 1080 kg/m(3)), wood flour contents (50, 60, 70, and 80 wt.%), wood flour sizes (= 0.5 to 1 mm), and hot-pressing temperatures (190 and 210 c) were manufactured using a dry blend/flat-pressing method under laboratory conditions. The surface smoothness of the WPC panels improved with increasing WPC density, plastic content, and hot-pressing temperature while it deteriorated with increasing wood flour size. The reduction in the particle size of the WF resulted in a more compact structure on the WPC surface. In general, the wettability of the samples increased by increasing surface roughness. (C) 2011 Elsevier Ltd. All rights reserved

Biological Characterization of Panels Manufactured from Recycled Particleboards using Different Adhesives

Transforming waste or recycled materials into value-added products is of high priority today. Wood plastic composites (WPCs) show high potential for the use of recycled materials in making durable composites. The applicability of WPC panels produced from recycled materials (ultralight foam core particleboards) for exterior building application was tested using wood-destroying basidiomycetes. The results showed that the panels were fully resistant against Coniophora puteana (Cp) and Gloeophyllum trabeum (Gt), but not very resistant against Pleurotus ostreatus (Po). The decay susceptibility index of Po-exposed specimens showed that the polystyrene-bonded (PS) samples were more resistant than solid beech wood samples that were used as references, followed by melamine-urea formaldehyde-bonded samples. A comparison with the reference samples also showed that the panel density had a significant influence on the panel’s resistance against basidiomycetes. The higher the panel density, the more resistance will be achieved in the panel

Properties of flat-pressed wood plastic composites containing fire retardants

This study investigated physical, mechanical, and fire properties of the flat-pressed wood plastic composites (WPCs) incorporated with various fire retardants (FRs) [5 or 15% by weight (wt)] at 50 wt % of the wood flour (WF). The WPC panels were made from dry-blended WF, polypropylene (PP) with maleic anhydride-grafted PP (2 wt %), and FR powder formulations using a conventional flat-pressing process under laboratory conditions. The water resistance and strength values of the WPC panels were negatively affected by increasing the FR content as compared to the WPC panels without FR. The WPC panels incorporated with zinc borate (ZB) gave an overall best performance in both water resistance and strength values followed by the panels containing magnesium hydroxide (MH) and ammonium polyphosphate (APP). For these three FR's, the best fire resistance as measured in the cone calorimeter was obtained with the 15 wt % APP treatment and then followed by 15 wt % ZB, or 15 wt % MH formulations

Analysis of Adhesive Distribution over Particles According to Their Size and Potential Savings from Particle Surface Determination

Wood and its processing into particles are, combined, the largest cost factor in the production of particleboard, followed by the cost of adhesive. Thus, reducing their cost is a goal of process optimization. This study investigated whether possible savings could be identified and quantified by determining the particle surface using automated three-dimensional laser-scanning technology (3D Particleview, Fagus-Grecon). The focus was on saving adhesive by sieving out adhesive-consuming fines. It was shown that, currently, with the actual prices for wood (89 €/t), particle preparation (37 €/t), and adhesive (570 €/t), the resulting additional costs for particles are overcompensated by the savings for adhesive with high adhesive content (e.g., 19%). The assumption of uniform distribution of adhesive on the total surface of all particles was checked for correctness using digital reflected light microscopy (VHX-5000, Keyence). Since urea-formaldehyde (UF) adhesive commonly used in particleboard production can only be detected with increased effort, phenol-formaldehyde (PF) adhesive was applied for the tests. Ultraviolet microspectrophotometry (UMSP) was used to rule out excessive penetration of the adhesive into the wooden tissue of the particles. The examination of the distribution of the adhesive over the surface showed that smaller particle sizes tended to be more heavily coated with adhesive. This means that the calculated savings still underestimate the real-life potential or that potential savings exist even with lower adhesive prices or higher prices for wood

Effects of fire retardants on physical, mechanical, and fire properties of flat-pressed WPCs

Physical, mechanical, and fire properties of the flat-pressed wood plastic composites (WPCs) incorporated with various fire retardants (10% by weight) at different levels of wood flour (WF) content, 40, 50, or 60 wt%, were investigated. The WPC panels were made from dry-blended WF, polypropylene (PP), and fire retardant (FR) powders with maleic anhydride-grafted PP (2 wt%) formulations using a conventional flat-pressing process under laboratory conditions. Incorporation of the fire retardants into the WPC panels significantly decreased the internal bond strength compared to the WPC panels without FR at all levels of the WF content. The modulus of rupture of the WPC panels containing FRs decreased with the increase in the WF content from 40 to 60 wt%. The modulus of elasticity increased with the increase in the WF content from 40 to 50 wt% and then decreased as the WF content reached 60 wt%. The WPC panels incorporated with zinc borate gave an overall best performance in both physical and mechanical properties followed by the panels treated with decabromodiphenyl oxide, magnesium hydroxide, and ammonium polyphosphate. Higher levels of the WF content resulted in significantly improved fire resistance of the WPC panels with and without FR as measured in the cone calorimeter. Of the four fire retardants tested, ammonium polyphosphate showed the most improvement over untreated ones

Density Profile Analysis of Laminated Beech Veneer Lumber (BauBuche)

An irreversible swelling was detected in laminated beech veneer lumber within the initial moistening. Supported by the facts that the lay-up of the glued veneers is exposed to high pressure during hot pressing, and that the density of the finished material exceeds that of solid beech, it was hypothesised that the wood substance is compressed. Laboratory X-ray density profile scans were performed to check this and to identify the part of the material cross section in which the densification has taken place. The higher density was found to be located in the area of the adhesive joints, uniformly over the cross section, while the density in the middle of the veneers corresponds to that of solid beech wood