Volume 12 Issue 3

Chinese herbal medicine extraction residue (CHER) is a special organic waste produced in China. Because of the high content of lignocelluloses, CHER have a weak bioconversion efficiency for bio-products production. This study investigates the effect of a hydrothermal pretreatment (HTP, 140 to 220 °C, 15 min) on the organic matter solubilisation, biochemical methane potential, and methanation kinetics of CHER during anaerobic digestion (AD). The AD test was conducted with 5 g/L total solid at 35 °C for 30 d. The results showed that the HTP clearly improved the solubilisation of CHER, and the obtained soluble COD (%) reached over 30% (only 4.5% in untreated). Acetic acid, xylose, and glucose were found to be the main products in the hydrolysate. The methane yield and methanation speed of the treated CHER were also enhanced. The highest methane yield of 306 mL/g volatile solid was achieved at a HTP temperature of 180 °C, while the untreated control was only 175 mL/g VS. Moreover, a carbonisation phenomenon was observed at HTP temperatures over 200 °C, which resulted in a loss of organic matter and methane yield.

The stepwise pyrolysis of technical lignin with and without a catalyst was investigated by pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). Lignin was first pyrolyzed at 260 or 360 °C, and then the residue was subsequently pyrolyzed at 650 °C. It was found that stepwise pyrolysis of lignin concentrated the phenolic compounds in lignin-derived bio-oil. In a stepwise 260 to 650 °C process, the maximum total phenolic compounds were 86.2%. Among the phenolic compounds, guaiacol-type and phenol-type phenolic compounds were predominant. Further addition of a catalyst (HZSM-5) in the stepwise pyrolysis process enhanced control over the product distribution through conversion of phenolic compounds into aromatic hydrocarbon products. The aromatic hydrocarbons achieved the highest yield of 30.4% in the catalytic stepwise 260 to 650 °C process.

The manufacture of poly(lactic acid) (PLA) composites reinforced with both oil palm empty fruit bunch (EFB) and cotton fiber was investigated. The positive and significant effect of EFB on the heat distortion temperature (HDT) and flexural properties was determined by a 2k design of experiment study. Adding solid epoxy into the PLA matrix manifested inferior mechanical properties with no improvement to the HDT. The HDT and mechanical properties of the biocomposites were further improved by using an EFB/cotton hybridized system. The PLA/hybridized EFB/cotton biocomposites showed biodegradability and an HDT higher than 100 °C. However, the flowability of the material was retarded at high cotton fractions. Finally, adding talc filler into the biocomposites improved the flowability of the hybridized biocomposite systems, especially at low fiber and high talc contents. Nevertheless, inferior mechanical properties of the biocomposites were found for high talc and low fibers’ contents.

A timber-concrete composite structure (TCC) is economically and environmentally friendly. One of the key design points of this kind of structure is to ensure the reliability of the shear connectors. The objective of this paper is to study the mechanical property of stud-groove-type connectors and to provide shear capacity equations for stud-groove connectors in timber-concrete composite structures. Based on the Johansen Yield Theory (European Yield Model), some mechanical models and capacity equations for stud-groove-type connectors in timber-concrete structures were studied. Push-out specimens with different parameters (stud diameter, stud length, groove width, and groove depth) were tested to obtain the shear capacity and slip modulus. The experimental strengths were used to validate equations given in the paper. The shear capacity and slip modulus of stud-groove-type connectors was in direct proportion to the diameter of studs and the dimension of the groove. Comparison between the theoretical and the experimental shear strength results showed reasonable agreement. The highlight of this study on shear capacity equations could significantly reduce the push-out tests before investigating the other properties of TCC.

Wood fibers were modified with alkaline solution and silane coupling agent to study changes on the fiber surface and the influence of these treatments on the mechanical properties, flame resistance, thermal conductivity, and microstructure of wood fiber-phenolic foam composites. Test results indicated that the lignin, waxes, hemicelluloses, and other impurities from the fiber surface were partially dissolved and removed. The mechanical properties of treated wood fiber-phenolic foam composites increased dramatically, the cellular pore distribution was more regular, the size of bubble cells was smaller and more uniform, and the thermal conductivity was reduced, and, in particular, the fragility of treated wood fiber-phenolic foam composites decreased. However, with increasing wood fiber content, the mechanical properties and limited oxygen index (LOI) of composite foam decreased. By comprehensive analysis, it was shown that the interfacial compatibility between the fibers and phenolic resin was improved. Nevertheless, the amount of wood used could not be too high, and the optimum amount was approximately 5%.

Although some engineered S. cerevisiae strains exhibit good xylose utilization ability, the lack of tolerance to inhibitors generated in biomass pretreatment limits the application of such strains in the production of bioethanol from lignocellulosic biomass. By applying a sexual mating method, inhibitor tolerance was developed in xylose-utilizing strains. The final ethanol concentrations in simultaneous scarification and co-fermentation (SScF) process at 38 °C with hybrid strains were 50% higher than the SScF process with the xylose-fermenting parent strain. The strain viability of the hybrid strain E7-12 at 24 h was 282 times higher than the parent strain in the SScF process at 25% solid loading. Due to the improved sugar utilization, the final ethanol concentration reached 69.7 g/L (E7-11) and 70.0 g/L (E7-12), which were 25.3 g/L and 25.6 g/L higher than that of SScF with the xylose-fermenting strain, respectively.

The impact of the trucking transportation network flow was modeled for the southern United States. The study addresses a gap in existing research by applying a Bayesian logistic regression and Geographic Information System (GIS) geospatial analysis to predict biorefinery site locations. A one-way trucking cost assuming a 128.8 km (80-mile) haul distance was estimated by the Biomass Site Assessment model. The “median family income,” “timberland annual growth-to-removal ratio,” and “transportation delays” were significant in determining mill location. Transportation delays that directly impacted the costs of trucking are presented. A logistic model with Bayesian inference was used to identify preferred site locations, and locations not preferential for a mill location. The model predicted that higher probability locations for smaller biomass mills (feedstock capacity, the size of sawmills) were in southern Alabama, southern Georgia, southeast Mississippi, southern Virginia, western Louisiana, western Arkansas, and eastern Texas. The higher probability locations for large capacity mills (feedstock capacity, the size for pulp and paper mills) were in southeastern Alabama, southern Georgia, central North Carolina, and the Mississippi Delta regions.