Volume 11 Issue 3

The production of cellulosic biofuels often leaves behind solid residues, which can be converted to useful co-products via chemical modification and processing. The objective of this study was to examine the changes in hydroxyl accessibility of a hardwood after the extraction of fermentable sugars (saccharification). Saccharification was performed on milled and dilute-acid pretreated aspen wood and resulted in a glucan-to-glucose conversion of 91%. The unhydrolyzed (solid) fraction was then analyzed for hydroxyl availability using an acetylation method, and the data were related to information of accessible pore volume evaluated using nitrogen adsorption. Different pore volumes were also created by oven-, air-, or freeze-drying of the samples. The results showed that more hydroxyls are available if the physical accessibility (pore volume) of a given substrate is better preserved. Upon saccharification, the accessible hydroxyls were reduced by at least half of that in untreated wood, while the specific pore volume increased 10 times. This finding suggests that future strategies for utilizing saccharification residues for co-products should tap the increased porosity and lower polarity of the substrate.

Phanerochaete chrysosporium treatment is less effective as a biological pretreatment on feedstock with larger particle sizes. We hypothesized that the improved effectiveness of the pretreatment when smaller particle sizes are used may be due to the inherently higher bulk density with smaller particle sizes. The effects of substrate bulk density and particle size on the efficacy of P. chrysosporium pretreatment of switchgrass (Panicum virgatum) was tested experimentally. Phanerochaete chrysosporium was grown on senesced switchgrass (2 different particle sizes) with various bulk densities. In all treatments, the fungal-pretreated samples released more glucose during enzymatic saccharification than the control sample. Substrate bulk density was a statistically significant factor in explaining the variation in the amount of glucose released per gram of substrate used. However, the particle size was not found to be a significant factor. On-farm switchgrass pretreatment may not require particle size reduction if the switchgrass is supplied in high-density bales.

There is currently a request from landowners in southeastern USA to provide a nondestructive tool that can differentiate the quality between stands of 25 and 30 years of age subjected to different thinning treatments. A typical site with various thinning regimes was used to vary the wood quality and to determine whether acoustics had the ability to separate for stiffness differences at a given age and local geography. A stand at age 29 with three different spacing (prior thinning) levels was chosen. Three hundred trees (100 per treatment) were randomly selected and acoustically tested for sound velocity using the Time-of-Flight (ToF) method for unthinned, thinned, and twice-thinned stands, respectively. The key finding of the study was that the estimated stiffness of the previously thinned treatments was actually greater than that of the unthinned group, despite having diameters as much as 28% larger. During a forest cruise, knowing that a higher-diameter stand is similar or higher in stiffness could raise the dollar value and harvest priority.

Five types of pretreatment processes were investigated to confirm the enhancement of the enzymatic hydrolysis of poplar. These processes included a hot water pretreatment, a calcium oxide pretreatment, NaOH extraction at low temperature, a Fenton reaction, and a combined dilute NaOH and Fenton pretreatment. The combined dilute NaOH and Fenton pretreatment was found to be the most effective pretreatment process. After enzymatic hydrolysis for 72 h, 74% of the cellulose recovery yield was obtained when the poplar substrates were pretreated with 2% NaOH at 75 °C for 3 h, followed by 20 mmol/g of H2O2 (30%) and 0.2 mmol/g of FeSO4·7H2O for a Fenton reaction period of 12 h. The cellulose recovery yield was approximately five-fold greater than that of the untreated sample directly processed by enzymatic hydrolysis. Furthermore, microscopic observations of changes in the surface structure of the pretreated residue were correlated with the enhancement of the enzymatic hydrolysis of cellulose. In conclusion, the combined dilute NaOH and Fenton pretreatment shows high potential for future application.

This study examined the combustion and thermal characteristics of domestic wood species in Korea. Wood was tested using a cone calorimeter according to the KS F ISO 5660-1 (2003) standard. The combustion properties of the wood were measured in terms of the heat release rate (HRR), total heat released (THR), mass lose rate (MLR), and ignition time (time to ignition; TTI). An optical microscope was used to determine the anatomical characteristics of wood. Also, the thermal properties were measured using thermogravimetric analysis (TGA) to determine the thermal stability of wood. The results of this experiment could be useful for fundamentals of guiding the combustion properties and thermal stability when using wood for various applications.

Xylose residue (XR), the abundant industrial residue from commercial xylose production, was delignified using alkali as a substrate for ethanol production via simultaneous saccharification and fermentation (SSF). It was found that pretreatment with 1.5% (w/v) NaOH at 140 °C for 1.5 h was optimal for delignification efficiency (72.2%) and low cellulose loss (7.1%). The physical changes in samples after alkaline pretreatment were characterized for crystallinity and imaged using scanning electron microscopy (SEM), which demonstrated that the surface of samples became coarser with lignin removal. There were rather significant changes in cellulose crystallinity. The widespread accessibility of cellulose in XR favored enzymatic hydrolysis and achieved considerable bioconversion (98.8% with 15 PFU/g substrate). The maximum for ethanol concentration using SSF bioconversion reached 16.3 g/L, which was about four times more than that of the untreated sample. XR treated using the processes of alkaline pretreatment and SSF was an excellent substrate for bioconversion.

Phenol and p-nitrophenol (PNP) are priority pollutants widely present in wastewater. Developing superior or low-cost sorbents for their removal would be of great benefit. Here, corncob residues (CCR) were converted to hydrochars via hydrothermal carbonization (HTC) and further upgraded to carbon materials by thermal activation in an N2 atmosphere. The influence of HTC conditions including the temperature, residence time, and CCR/water weight ratio on the material properties and their performance for removing phenol and PNP from water were investigated and compared with those that were obtained from pyrochar (directly pyrolyzed CCR). Hydrochars showed lower adsorption capacities for phenols than pyrochar. The initial hydrothermal treatment at 220 °C and 2 h resulted in an improved porosity and 4- to 5-fold higher adsorption capacities for phenol and PNP compared with the pyrochar. However, hydrochars prepared at 250 °C or with a prolonged residence time (4 and 6 h) could not be upgraded to high performance carbon materials by thermal activation. The adsorption isotherms of both phenols on the best performance material were well correlated by the Sips model.

The objective of this study was to evaluate the adhesion strength and glossiness of black alder wood (Alnus glutinosa Gaertn. L.) coated with water-borne and UV varnishes by two application systems. Prior to coating, the samples were prepared by sanding with four combinations of grit size sandpapers, 180 being the final grit. The surface quality of the specimens was measured with a white light profilometer. Any increase in grit size gradually reduced surface roughness, which further influenced the overall coating performance of the samples. UV varnish applied by roller presented higher adhesion strength and gloss as compared to spraying. The specimens varnished with a water-borne finish by spraying exhibited a better adherence to the substrate than those of UV varnished samples by the same method and provided glossiness at 60° geometry in the same range. These results are valuable for the furniture manufacturing industry for generating a better use and efficiency of secondary wood resources in order to achieve value-added products.

The wide use of natural fibers has a long-standing history in Africa. In northern Angola, three native fiber plant species, namely Urena lobata, Triumfetta cordifolia, and Dombeya burgessiae, were investigated with regard to their potential usage in modern applications, such as green composites. Bast fibers of the three species were analyzed morphologically, chemically, and mechanically to determine properties such as fiber density, cellulose content, Young’s modulus, tensile strength, and breaking strain. In comparison to other natural fibers, all three species were characterized by high Young’s moduli up to 60 GPa and tensile strengths up to 950 MPa, yet retting is crucial to unfold the maximum strength of the fibers. Extending the retting time revealed higher values but probably negatively influences economic efficiency. The results demonstrated that the analyzed plants deliver strong and resistant fibers; based on their biomechanical performance, they are alternatives to commercially used natural fibers, such as jute (Corchorus spp.). However, as with other natural fibers, there was high variation in the mechanical properties in the studied species.

Lightweight sandwich engineered wood reinforced with fiber glass using a natural fiber wood foam core was investigated. A prepreg epoxy formulation was used as both wood adhesive and matrix for the prepreg fiber glass. Combining 3 phr of oxybis(benzenesulfonylhydrazide) (OBSH) with 10 phr of ethyl acetate, as foaming agent enhanced the properties of the eucalyptus fiber (EF) wood foam. Incorporation of rice-husk fiber (RF) or bagasse (BG) into the EF reduced the mechanical properties due to the low aspect ratio and high non-compacted bulk density of RF and BG. The high hydrophilicity of BG increased the water uptake and decreased the dimensional stability of the wood core. The mechanical performance of the natural fiber cores was improved by using randomized unidirectional engineered glass (GF), carbon (CF), and Kevlar (KF) fibers. However, the hybridized cores with long fibers and high elastic modulus, with respect to the sample thickness, had a negative impact on the woods due to internal residual stress, leading to a spring-back effect. A fiber glass reinforcement lightweight sandwich structure with engineered wood derived from the EF/BG and its 30% hybrid lightweight cores yielded superior mechanical and durability properties.