Volume 15 Issue 2

This study focused on stress and strain analysis of the cutting force of a branch knife with a replaceable cutting edge. The replaceable edge forms part of the delimbing head, which is applied to the arms of a mechanical harvester working in forestry. Basic parameters of the knife and head of the harvester with the basic calculations necessary to determine the number of knives based on input parameters, such as wood diameter, woody plants, and determination of the cutting force acting on the cutting knife, were examined. Based on the cutting force and the design of the special cutting knife, a stress analysis and a finite element method (FEM) was performed. This study confirmed the correctness of the selected material to produce the delimbing knife, which was designed using a replaceable cutting edge. The output of the stress analysis is reported.

Cellulose nanofibril (CNF) is a class of promising and renewable nanocellulosic material due to its unique dimensional characteristics and appealing properties. CNF preparations based on TEMPO pretreatment followed by high-pressure homogenization have been studied intensively, while the high energy consumption and the environmental issues remain challenges to their application. Mechanical refining processes have been commonly applied at the academic and industrial relevant scales for CNF production. In this study, bleached softwood kraft pulp was subjected to high-efficiency wet ball milling (following enzymatic pretreatment) and mechanical grinding to obtain CNF. The effects of ball milling time, grinding gap, and grinding passes on structure and properties of CNF were evaluated. Scanning electron microscopy images confirmed that the diameter of CNF was decreased with the increment of ball milling time and number of grinding passes. The results indicated that ball milling time, grinding gap, and grinding passes were important to increase the dispersity of CNF suspensions. The degree of polymerization and crystallinity index of CNF decreased with increasing ball milling time and grinding passes.

The weathering resistance properties of short cycle coconut trunk lumber (SC-CTL) were evaluated in response to impregnation using kraft black liquor (BL) and black liquor/phenol formaldehyde (BL/PF) resin. Concentrations of 10, 15, 20, and 25% w/w kraft BL and PF resin with BL were impregnated into SC-CTL using a vacuum-pressure method. Natural weathering tests lasting 6 and 12 months were performed according to ASTM D1435 (1999). After the prescribed testing period, samples were analyzed for their morphological changes via FT-IR and SEM. Mechanical tests were conducted to analyze changes caused by natural weathering in impregnated SC-CTL. The results showed that BL with PF resin impregnation into SC-CTL improved the resistance against natural weathering. The SEM study confirmed that fungi could not colonize the treated samples. The results also suggested that addition of 20% BL in PF resin was sufficient to inhibit weathering. Thus, it was concluded that impregnation of PF resin with BL is a good method to improve the mechanical properties of SC-CTL.

Complementary enzymes can considerably enhance the hydrolysis effectiveness of cellulase. The influence of hemicellulase supplementation on high solids saccharification of alkali-pretreated sugarcane bagasse was assessed. Hemicellulase addition of 1200 IU/g substrate with cellulase loading of 10 FPU/g substrate achieved high sugars yield with glucose and xylose conversion efficiency of 95.4% and 87.4%, respectively. To further improve the substrate conversion efficiency based on high sugars production, fed-batch hydrolysis was employed with high solids loading of 20% (w/v) to 25% (w/v). After 96 h hydrolysis with 25% solids loading at cellulase and hemicellulase loading of 20 FPU/g and 1200 IU/g substrate, respectively, the obtained highest total sugars was 242 g/L, with glucose and xylose conversion efficiencies of 98.6% and 94.9%, respectively. An increase in substrate digestibility upon supplementation of mixture enzymes with high sugars production can be realized in high solids fed-batch system with proper cellulase and hemicellulase synergism.

Nine kinds of biomass were used to investigate the correlation of organic composition with the methane yield in continuous anaerobic digestion (AD) mode with different organic loading rates (OLRs). The experimental results showed that the methane yields were different with the change of OLR; thus, only one model was unable to satisfy the prediction accuracy for all the operation conditions. A stepwise regression model and two self-defined models were used to determine the prediction accuracy for different operation OLRs in the present assay. The results showed that the self-defined models constituted by biodegradable components (protein, fat, and readily degradable sugars) obtained a higher determination coefficient (R2) than the model fitted by the traditional stepwise regression method. Biomass with a higher content of easily degradable matter had a lower predictive deviation. Based on this, it is recommended that the various biomasses be divided into two groups to obtain better model fitting and prediction accuracy. The biomass with a content of readily degradable section that was more than 47% or the content of lignin was less than 8% can be classified into one group, and the others can be classified into another group according to the present test results.

In various engineering applications, self-tapping screws are used to connect timber members. To describe their load-deformation relationship, a better understanding of the strain along the mechanical interface (i.e., timber-screw interface) is required. With a focus on the axial loading of self-tapping screws, only a few studies have dealt with the determination of the strain based on optical measurement techniques. Therefore, in the present study, the strain distribution at the timber-screw interface was monitored during pull-out tests using an optical measurement technique, called electronic speckle pattern interferometry (ESPI). Strains obtained from the ESPI measurements were compared with the results obtained from structural simulations conducted with finite element modelling (FEM). Three different types of solid spruce wood (Picea abies (L.) Karst.) specimens with different grain orientations connected with self-tapping screws (thread length lg = 130 mm, outer thread diameter d = 12 mm) were tested in withdrawal. There was a good agreement between the ESPI and FEM results, confirming that ESPI was a suitable measurement technique. The study also provided insights and results regarding the region of strain concentrations across the length of self-tapping screws.

In recent years, the capital investment amounts flowing into the forest products industry in the southeastern United States have been unequal from state to state. Reasons for this have been informally hypothesized, but the topic has not been researched in depth. An economic model was tested that will aid relevant stakeholders in addressing this problem. The model utilizes a combination of county-level and state-level data related to lumber manufacturing and a linear programming solver to produce estimates of variable costs for a mill built in any Southeastern county. The variable costs considered by the program include raw materials, labor, electricity, and transportation costs (which are paid by the customer). Future versions of the model will consider non-financial metrics such as timber supply, socioeconomic statistics, and competition for timber-consuming facilities. This model could be exceptionally useful to those involved in industry recruitment efforts, as it provides them with an objective method for evaluating counties in both their state and competing states.

Absorption capacity is a key feature of toilet tissue papers. Several parameters can affect their final absorption capacities, such as pulp composition, stock preparation, number of sheets, additives, bulk, grammage, and converting process parameters, such as the embossing operation. In this work, the absorption capacities of four different 2-ply industrial toilet tissue papers, as well as the respective base papers from the mother-reel was compared using the immersion method according to ISO 12625-8 (2010). Previously, these samples were characterized in terms of morphology, grammage, thickness, and bulk. It was concluded that the embossing operation noticeably increased the thickness and bulk of toilet tissue paper. Furthermore, it was also verified that among the various toilet tissue paper samples there was not a noticeable variation in the time of water absorption because the samples revealed similar morphology and porosity. However, it was found that the bulk increased more than 150%, resulting in an increase of water absorption capacity over 60%.

Greenhouse gas (GHG) emission levels are causing concern as climate change risks are growing, emphasizing the importance of GHG research for better understanding of emission sources. Previous studies on GHG emissions for the pulp and paper industry have ranged in scope from global to regional to site-specific. This study addresses the present knowledge gap of how GHG emissions vary among paper grades in the US. A cradle-to-gate life cycle carbon analysis for 252 mills in the US was performed by integrating large datasets at the production line level. The results indicated that one metric ton of paper product created a production weighted average of 942 kg of carbon dioxide equivalent (kg CO2eq) of GHG emissions. Greenhouse gas emissions varied by pulp and paper grade, from 608 kg CO2eq per metric ton of product to 1978 kg CO2eq per metric ton of product. Overall, fuels were the greatest contributor to the GHG emissions and should be the focus of emission reduction strategies across pulp and paper grades.

Black poplar (Populus nigra L.) was thermally modified in superheated steam at 160 °C, 190 °C, and 220 °C for 2 h. The research identified correlations between the chemical composition and selected mechanical properties of thermally modified wood. The higher treatment temperatures significantly lowered the modulus of rupture (MOR) and the Brinell hardness (BH). These correlations were particularly apparent at higher temperatures (190 °C and 220 °C) when thermally modified wood experienced stronger hemicelluloses degradation, which was indicated by an increase in the content of non-structural substances. The wood properties including compressive strength parallel to the grain (CS), modulus of elasticity during bending (MOE), and compressing (MCS) were affected less by the chemical changes caused by the thermal processing of wood. Moreover, the level of wood moisture content also affected these changes.