Volume 14 Issue 2

The effect of sanding, as the last operation before finishing, on the quality of heat treated wood surfaces has been insufficiently explored and explained. This paper compared the effects of sanding with three commonly used sanding grit sizes P60, P100, and P150 on the surface roughness values of beech (Fagus sylvatica L.) wood. The wood samples were treated by the ThermoWood process at 200 °C for 2.5 h. A large range of standard roughness parameters (Ra, Rq, Rv, Rt, RSm, Rsk, Rk, Rpk, and Rvk) and two waviness parameters (Wa, and Wt) were included in the analysis, as well as environmental scanning electron microscope (ESEM) images of the sanded surfaces. The results showed that the heat treatment slightly increased the surface roughness and decreased the wood surface waviness after sanding. All roughness and waviness parameters increased with increasing sanding mean grit diameters by following a strong linear correlation. The processing roughness was closely approximated by the parameter Rk. For both, treated and untreated beech, sanding had a tendency to obscure (in magnitude and number) wood anatomical details in the measured data. However, the influence of wood anatomy in the valleys domain increased as the grit size became finer.

The accurate measurement of wood dielectric properties and their relationship with many influencing factors are not only necessary for the study of other relevant wood properties, but also improve the wood dielectric moisture content detection method. In this study, the relationships between dielectric properties and frequency, as well as between moisture content and texture direction were analyzed. The results showed that the effect of the moisture content on the dielectric constant is significant. With increasing moisture content, the dielectric constant increased exponentially below the fiber saturation point. The effect of texture direction slightly exceeded that of the radial direction, and the change rate of the tangential direction above the fiber saturation point was higher than that of the radial direction. The relationship between the dielectric constant and frequency was related to the wood moisture content. The dielectric loss was approximately linear with the frequency below the fiber saturation point.

One of the major challenges in transforming from fossil to bio-based materials is the production of biomass-derived intermediates in a well-described, reproducible manner at a relevant scale. Lignin, as the only renewable aromatic resource, will play an important role in the future bioeconomy. Various grades of lignin were produced at Fraunhofer CBP’s pilot plant by variations of the following parameters: raw material (beech wood, spruce wood, and wheat straw), H-factor (combining the effect of temperature and time), addition of sulfuric acid ω(H2SO4), and the precipitation procedure. During the optimization of the process conditions for lignin production an in-depth analytical characterization was done by acid hydrolysis with subsequent anion-exchange chromatography (AEC), elementary analysis, 31P-nuclear magnetic resonance spectroscopy (NMR), size-exclusion chromatography (SEC), and differential scanning calorimetry (DSC) to monitor changes in structure and selected properties.

Pine (Pinus strobus) sawdust (PSD), a sawmill waste, was used as a precursor for the preparation of activated carbon through a chemical activation technique with phosphoric acid at 600 °C (100 min). Phosphoric acid pine sawdust activated carbon (PSDP) was characterized and used for the adsorption of methyl orange (MO). The textural examination was applied to determine the total pore volume and specific surface area of PSDP. Carbon surface functional groups were identified utilizing Fourier transform infrared spectroscopy. The effects of pH, contact time, and adsorbent mass on the sorption were investigated in a batch procedure mode. Kinetic information was studied that followed the pseudo-second-order model. The results showed that PSDP could be used as a low-cost adsorbent for MO adsorption from waste effluents.

Fern root (FR) was used in the biofuel production for the first time. However, fermentation of the enzymatic hydrolysate of FR starch (EHFS) directly to butanol by Clostridium acetobutylicum CGMCC1.0134 resulted in a low butanol production and yield with high content of starch residual. After adding yeast extract (YE) solution (with a 3 g/L final concentration in broth) into EHFS, the butanol production, productivity, and yield were raised by 174%, 250%, and 183%, respectively. Monitoring changes of free amino acid concentration in the fermentation broth indicated that aspartic acid families and serine families were stimulated to accumulate by YE addition. Gene expression analysis further revealed that ctfB coding CoA-transferase was induced by adding YE into EHFS. It was concluded that EHFS could be a promising substrate for butanol fermentation.

Reforestation wood is interesting for construction, due to its potential as material source for manufacturing. For this purpose, the Eucalyptus genus has resulted in a better characterization of the material properties. During the production process, wood is machined at some stage, which influences the wood gluing quality. This study considered the performance of Eucalyptus saligna wood joints bonded with four commercial polyvinyl-acetate-based resins with different physical characteristics and chemical compositions. The surfaces of samples were prepared and machined by an up-milling process, using a planer, with wood feed rates of 6 m/min, 11 m/min, 16 m/min, and 21 m/min, which had advances per tooth of 0.25 mm, 0.45 mm, 0.66 mm, and 0.87 mm, respectively. The samples were prepared for shear strength testing of the glue line. During the preparation, all pieces were randomly bonded with regards to the formation plans of wood growth rings. Shear strength values were statistically compared to analysis of variance and Tukey test. Only C4 adhesive reached good results at all feed rates as well as having the best shear strength compared to other resins. Commercial adhesives had distinct interactions on the adhesive-wood interface, which resulted in different adhesion strengths.

The development of a clean and sustainable pretreatment is of great importance for the production of fermentable sugars. In this study, an ammonium sulfite (AS) pretreatment of wheat straw was optimized based on response surface methodology with a three-level, three-factor Box-Behnken design. The investigated factors were AS dosage, pretreatment time, and pretreatment temperature. The effectiveness of the AS pretreatment was evaluated using the standard enzymatic hydrolysis procedure. A second-order polynomial fit was performed to fit the experimental data, and the model analysis showed that the effect of the AS dosage on the final total sugar yields was much more significant than that of the other two factors. Under the optimum pretreatment conditions (27% of the AS dosage (based on the dry wheat straw) at 160 ºC for 63 min), the final total sugar yield achieved was 74.4% after saccharification, which was in agreement with the predicted value (76.5%). Furthermore, it was found that pre-impregnation with acetic acid before AS pretreatment or the post-mechanical refining after AS pretreatment could further increase the fermentable sugar yields to approximately 77%. In addition, the spent liquor containing nitrogen could be used for the production of lignin-based fertilizer, thus making the whole process clean and sustainable.

In order to minimize the waste of polysaccharides (hemicellulose and cellulose) during preparation of platform chemicals (furfural and levulinic acid) from lignocellulose in one-pot acid/organic solvent systems, a novel two-step biorefinery system was developed based on sugarcane bagasse fractionation with a phosphoric acid/acetone pretreatment method. The effect of different pretreatment conditions on sugarcane bagasse fractionation was studied at first. Under the optimal condition (5 g bagasse, 40 mL 85% phosphoric acid, 50 °C, 1 h, precooled acetone), 72.5% xylose and 74.5% glucose (the residual biomass from pretreatment) were obtained. Acetone was evaporated and removed from the acetone extract, and then the soluble lignin was precipitated and recovered through the addition of water in the extract. The water solution (containing phosphoric acid and 20.8% xylose) and washing water from residue (containing 41.7%% xylose) was combined to produce furfural at 180 °C. Meanwhile, the potential of LA generation from cellulosic residue was evaluated via glucose conversion in different phosphoric acid/acetone systems.

The enzymatic hydrolysis of lignocellulosic biomass into fermentable sugars remains a critical challenge for producing bio-based products due to complexity and recalcitrance of the biomass. The effects of mechanical pretreatments (i.e., wet grinding for corncob residues and PFI refining for wood fibers) on the enzymatic hydrolysis of mixed substrates of corncob residues (CRs) and wood fibers (WFs) were investigated. The results showed that the applied combined mechanical pretreatments noticeably enhanced the enzymatic digestibility of the mixed substrates. A 99.8% conversion yield of cellulose to glucose and 19.2 g/L glucose concentration were obtained when the mixed substrates (composed of the refined WFs and the ground CRs) were enzymatically hydrolyzed for 46 h. The improvements, including swelling ability, specific surface area, and morphology, were mainly attributed to the combined mechanical pretreatments.

Biochar produced by the pyrolysis of biomass can be used to counter water pollution from heavy metals. The purpose of this work was to develop a biosorbent based on soy sauce residue (SSR) for the removal of Cr6+ and Pb2+. The SSR biochar (SBC) from oxygen-limited pyrolysis under the temperatures of 300 to 700 °C were obtained, and their adsorption capability was evaluated. After determining the optimum pyrolysis temperature, the effects of initial pH values, contact times, and initial metal concentrations on the Cr6+ and Pb2+ adsorption by SBC prepared at 600 °C (SBC600) were investigated. With the increase of pyrolysis temperature, the physical and chemical properties of SBC developed in a direction favorable to heavy metal adsorption. The SBC600 reached the adsorption equilibrium at the time of 2 (Cr6+) and 24 h (Pb2+), and the maximum adsorption amounts of Cr6+ and Pb2+ were 25.80 and 135.3 mg/g, respectively. The adsorption kinetics followed the pseudo-second-order kinetic equation, and the adsorption isotherms was best described by the Langmuir isotherms. The SBC was an adsorbent with certain potential for heavy metals removal in wastewater.