Volume 10 Issue 3

The assembly of functional cellulolytic enzymes was displayed using a synthetic, cell-surface engineered diploid yeast consortium. Trichoderma reesei endoglucanase II (EGII), cellobiohydrolase II (CBHII), and Aspergillus aculeatus β-glucosidase I (BGLI) were displayed as fusion proteins with the AGA2p C-terminus of a-agglutinin on the cell surface of the diploid yeast strain Saccharomyces cerevisiae Y5. The cell-surface immobilization of each enzyme was confirmed by immunofluorescence microscopy. This type of yeast consortium allowed convenient optimization of ethanol production by adjusting the combination ratios of each cell type for inducing synergy in cellulose hydrolysis. Next, the direct ethanol fermentation from steam-exploded corn stover was investigated. The optimized cellulase-displaying consortium produced 20.4 g/L ethanol from 48.4 g cellulose per liter after 72 h in the presence of a small amount of cellulase reagent (0.9 FPU/mL). These results suggested the feasibility of the cellulase-displaying yeast consortium for simultaneous saccharification and fermentation from insoluble cellulosic materials.

Bending and shear stiffness, which are used as deformation resistance indexes, are very important mechanical properties of bamboo-wood sandwich composites. Thus, a new methodology to calculate the elastic constants of this type of material was proposed in this paper. First, the elastic constants of the composites were derived based on composite mechanics. In particular, the equivalent shear stiffness and modulus were determined by the energy method. Then, the three-point bending test and a revised three-point bending test were used to verify the accuracy of the theoretical model, which uses the properties of the skin and core layers as its input parameters. The model was subsequently evaluated. The results show that, generally, the predicted values were slightly smaller than the test results for the same bamboo-wood composite because of the strengthening of the wood veneer after hot-pressing.

Bio-oil from the pyrolysis of biomass is an important renewable source for liquid fuel. However, the application of bio-oil has been severely restricted due to its high viscosity, acidity, and low heating value. Thus, it has been necessary to upgrade bio-oil for automobile fuel via catalytic deoxygenation reactions. Herein, the effects of the zeolite ZSM-5 on the pyrolysis of four biomass materials (corn cob, corn straw, pine powder, and cellulose) were investigated via TG-FTIR (thermogravimetric analyzer coupled with a Fourier transform infrared spectrometer) to better understand the working mechanism of ZSM-5. The contents of the products of H2O, CO, CO2, and the C-O, C=O, and OH groups evolved with increasing pyrolytic temperature were monitored by FTIR. It was found that the relative contents of the C-O and C=O groups were decreased under the catalysis of ZSM-5, while the formations of CO, H2O, and the OH containing compounds were promoted. To explain the regulations, reaction routes were speculated and the catalytic conversion mechanisms were deduced.

Raw biomass is not commonly suitable as feedstock for existing power plants, mainly because of the substantial required infrastructural changes. As a result, most raw feedstock requires pre-treatment to improve its physical and thermal characteristics. Biomass carbonization is one of the pre-treatments that produces charcoal-like feedstock. This paper explores the effects of the carbonization process on the physiochemical characteristics of biomass produced from two cottonwood clones, S7C20 and ST66, and switchgrass (var. Alamo). Additionally, it studies the thermal degradation kinetics of raw and carbonized agroforestry products in nitrogen and air environments. Feedstock samples were carbonized in a batch reactor at 400 °C in an oxygen-free environment for 2 hours. Carbonization decreased biomass bulk density, moisture content, and volatile solids while increasing fixed carbon, ash content, pH, and heating values. The heating value of S7C20, ST66, and switchgrass increased by 58.6%, 60.3%, and 69.7%, respectively. Carbonization increased the activation energy values under the condition of pyrolysis and decreased these values under the condition of combustion. The carbonization process produced a charcoal-like feedstock that may be processed with coal or even replace it.

A series of novel membrane materials were prepared based on liquefied banana pseudo-stem (LBPS) blended with various proportions of polyvinyl acetate emulsion (PVAc). The mechanical properties, structure, thermal stability, and cross-sectional morphologies were investigated using a universal testing machine, Fourier transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TGA), and scanning electron microscopy (SEM), respectively. The addition of LBPS to PVAc led to a structural change, and this change depended on the reaction temperature. The enhancement of elongation and the thermostability of membranes is attributed to an increase in C-O-C groups. Furthermore, the LBPS/PVAc membranes have a higher water resistance.

The possibilities of utilizing an abundantly available agricultural waste, oil palm empty fruit bunch (OPEFB) fibers, for the development of nano-filler was investigated. The aim was to develop fire retardant nano-fillers from OPEFB fiber through grinding, chemical treatment (bromine water and SnCl2), and cryogenic crushing, followed by a high energy ball milling process. The structural, morphological, and thermal properties of nano-fillers were investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The analysis revealed that the particle size distribution was reduced from micro to nano size in the range of around 14 to 100 nm. Scanning electron microscopy (SEM) observations revealed that the nanoparticles of OPEFB had irregular shapes. The elemental composition of the OPEFB were investigated by elemental dispersive X- ray analysis (EDX), showing the presence of tin, carbon, oxygen, chlorine, and bromine elements both before and after ball milling. Further, thermo-gravimetric analysis (TGA) and differential scanning calorimetry (DSC) indicated that the developed nanofillers exhibited enhanced thermal properties compared to the untreated fibers. Such results suggest that the developed nano-filler can be used for the fabrication of nanocomposites with improved fire retardancy.

This paper explores the evolution in the tensile strength of orange pruning fiber-reinforced polypropylene composites. The exploitation of these pruning’s can effectively avoid incineration, with the consequence of CO2 emissions and fire risk, while extending the value chain of the agricultural industry. This biomass was subjected to three different treatments yielding mechanical, thermomechanical, and chemi-thermomechanical pulps. It was found that 20 to 50% of these pulps, together with a coupling agent, were used as polypropylene reinforcement. The evolution in the tensile strength and morphological properties of the fibers, and the effect of treatments on these properties were analyzed. A modified rule of mixtures (mROM) was used to analyze the micromechanical properties of the interface. In addition, the mechanical properties were weighted against the fiber treatment yields. Finally, factors to compute the net contribution of the fibers to the final strength of the composite materials were proposed.

Physical, mechanical, and thermal properties of wood flour reinforced ungrafted and maleic anhydride grafted unsaturated polyester biocomposites were investigated. Composites were prepared using a Resin Transfer Moulding technique by varying wood flour loading (10, 15, 20, and 25 wt%) for both ungrafted and maleic anhydride grafted unsaturated polyester. Fourier transform infrared (FTIR) spectroscopic and scanning electron microscopic (SEM) analysis was utilized to study physical properties. Tensile and flexural tests were conducted for mechanical characterization, while thermal properties were evaluated using thermogravimetric analysis (TGA). FTIR and SEM results confirmed the presence of grafting onto the unsaturated polyester. The flexural strength and modulus of the composites were increased up to 20% filler loading, after which those values decreased, whereas, the tensile strength and Young’s modulus values increased only up to 15% filler loading. Maleic anhydride grafted composites had better mechanical properties compared to ungrafted composites. According to TGA results, maleic anhydride grafted composites showed enhanced thermal stability at the final decomposition stage.

A scheme for using a two-stage cyclone gasifier for high-temperature rice husk pyrolysis and gasification to reduce the tar content in biogas is presented in this study. The two-stage cyclone gasifier consisted of an upper cyclone high-temperature pyrolysis chamber and a lower steam spray gasifier. The staging pyrolysis and gasification process used in this study can increase the carbon conversion efficiency and reduce tar content by increasing the pyrolysis temperature. This process uses part of the produced gas for combustion in an external burner to generate high-temperature (1600 °C) anaerobic flue gas and to provide heat for pyrolysis and gasification. This study simulates the isothermal gas phase and the gas-solid flow field for the upper cyclone chamber, as well as the gas-solid flow field, with steam (heat transfer between the steam and the gas is considered), for the entire gasifier by varying the structural and operational parameters. The optimal parameters for the cyclone gasifier for good mixing and lengthy residence (2.3 to 4.8 s) of the rice husk particles were found to be inlet angles of 20° and 30° with inlet velocities between 40 and 80 m/s.

Oxalate exists in plant tissue in the form of soluble and insoluble salts. Determination of the oxalate content in a raw material is important for controlling oxalate scaling during the pulping and papermaking processes. In this study, oxalate extraction and determination of the total and soluble oxalate contents in several pulping and papermaking raw materials were investigated. It was found that soluble oxalate can be extracted completely by distilled water at 70 °C within 180 min. Total oxalate can be extracted completely by 2-mol/L hydrochloric acid at 70 °C within 210 min.