Volume 9 Issue 2

This paper evaluates the optimal composition of annual and perennial biomass feedstocks for a biorefinery. A generic optimization model is built to minimize costs – harvest, transport, storage, seasonal, and environmental costs – subject to various constraints on land availability, feedstock availability, processing capacity, contract terms, and storage losses. The model results are demonstrated through a case study for a midwestern U.S. location, focusing on bioethanol as the likely product. The results suggest that high-yielding energy crops feature prominently (70 to 80%) in the feedstock mix in spite of the higher establishment costs. The cost of biomass ranges from 0.16 to 0.20 $ l-1 (US$ 0.60 to $0.75 per gallon) of biofuel. The harvest shed shows that high-yielding energy crops are preferably grown in fields closer to the biorefinery. Low-yielding agricultural residues primarily serve as a buffer crop to meet the shortfall in biomass requirement. For the case study parameters, the model results estimated a price premium for energy crops (2 to 4 $ t-1 within a 16 km (10-mile) radius) and agricultural residues (5 to 17 $ t-1 in a 16 to 20 km (10 to 20 mile) radius.

The effect of chip thickness, rake angle, and edge radius on cutting forces and chip morphology in wood plastic composites (WPCs) orthogonal cutting was investigated. Three types of WPCs, Wood flour/polyethylene composite (WFPEC), wood flour/polypropylene composite (WFPPC), and wood flour/polyvinyl chloride composite (WFPVCC), that were tested exhibited different behavior with respect to the machinability aspects. The cutting forces of WFPVCC were the highest, followed by WFPPC and WFPEC. The most significant factor on the parallel cutting force of these three types of WPCs was the chip thickness, which explained more than 90%, contribution of total variation, while rake angle, edge radius, and the interactions between these factors had small contributions. The most significant factor on the normal cutting force of WPCs was also the chip thickness, which accounted for more than 60% of the total variation. The chips produced included long continuous chips, short continuous chips, flake chips, and granule chips when cutting these three types of WPCs.

The strength of the adhesion between the paper and the drying Yankee cylinder is of great importance with respect to the final properties of a tissue paper product. Therefore, the effects of a few potentially important pulp properties have been evaluated in laboratory experiments. Four highly different kraft pulps were used, and the adhesion strength was measured by means of the force required when scraping off a paper from a metal surface with a specifically designed knife mounted on a moving cart. The adhesion strength was observed to increase with increasing grammage and increasing degree of beating of the pulp. It was also found that pulps containing more fines, or with higher hemicellulose content, gave rise to higher adhesion strength.

Fibrillation of chemical and mechanical pulps with different lignin contents was studied. The pulps were ion exchanged into their sodium form prior to fibrillation and fibrillated with an increasing level of energy using high-shear friction grinding. The fibrillated samples were characterized for their chemical composition, morphology, rheological properties, and water retention capacity. All pulps had a distinct tendency to form fibrillated material under high shear and compression. The lignin-containing kraft pulps fibrillated easily, and the resulting material can be utilized in applications where high viscosity, water retention capacity, and reinforcement are desired. Fibrillation of mechanical pulps resulted in more heterogeneous samples, which included fiber fragments, branched fibrillar structures, and flake-like particles. This material showed relatively low viscosity and water retention capacity when compared to the samples made from kraft pulps. Chemi-thermomechanical pulp (CTMP), when used as the raw material, yielded a more homogeneous organic filler-like material than did thermomechanical pulp (TMP).

The effects of the chemical modification of peanut shell powder (PSP) using polyvinyl alcohol (PVOH) were studied. Both modified and unmodified peanut shell powder were used to prepare recycled polypropylene (RPP) and PSP composites. The effects of various PSP loadings (0 to 40% by weight) on the processing, tensile properties, morphology, Fourier transform infrared (FTIR) spectra, and water uptake properties were examined. Results showed that RPP composites with polyvinyl alcohol-modified PSP had higher values of tensile strength, elongation at break, and tensile modulus, but lower water resistance, than RPP composites with unmodified PSP. FTIR analysis revealed slight changes in band positions and intensities, indicating a distinct interaction between hydroxyl groups of the PSP composites and PVOH. RPP composites with PSP modified with PVOH had better interfacial adhesion between the matrix and the filler than RPP composites with unmodified PSP, as shown by scanning electron microscope (SEM) micrographs.

To demonstrate the feasibility of bioaugmentation in enhancement of the biodegradation of pulping effluent, aerobic sludge was intensified with superior mixed flora. The differences between intensified aerobic activated sludge and original sludge were compared. The results showed that the chemical oxygen demand (COD) of pulping effluent treated with the intensified sludge dropped to a much lower level compared with the original sludge, which indicated that the biodegradability of sludge was enhanced by bioaugmentation. The growth kinetics of the sludges were established. The growth rate Vmax of the intensified sludge was elevated from 7.8×10^-3 to 7.1×10^-3, while the saturation constant Ks decreased from 0.33 to 0.21 after bioaugmentation. In addition, the degradation kinetics showed that the equation coefficient of sludge increased from 4.6×10^-3 to 6.4×10^-3, confirming the intensification of biodegradation as a result of bioaugmentation.

In this work, the thermomechanical pulp of Pinus massoniana was pretreated with a NaOH/thiourea/urea aqueous solution to promote fiber bonded area and to increase paper strength. The effects of pulp concentration, alkali dosage, dipping time, and freezing time were evaluated through single factor experiments. The optimum conditions were found to be 15% pulp consistency, 8% NaOH, a dipping time of 15 min, and a freezing time of 60 min. Under these conditions, the paper tensile and burst index of treated pulp increased nearly 100%, and the bulk also was reduced by 10%, but there were no significant effects on folding.

Cellulose was extracted from kenaf core powder by a series of bleaching processes and subsequently dissolved using an alkaline LiOH/urea solvent at low temperatures. The produced cellulose solution was mixed with polyvinyl alcohol (PVA) with different ratios of cellulose/PVA and coagulated to produce regenerated transparent films. The films were then air dried to produce transparent film. The effects of PVA content on tensile index, transparency, pore size, and printability of the films were studied. A slight reduction of 7% on the tensile index of the film was observed when the content of PVA increased to 10%. Nevertheless, the addition of 10% of PVA increased the porosity of the regenerated cellulose/PVA film, while the transparency of the film increased by 10%. The films were color-printed using a laser printer and can be recycled, in which the printed ink can be removed easily from the films with higher amount of PVA content. In addition, the films can be reprinted repeatedly several times.

Two tropical biomass species, teak (Tectona grandis) and obobo (Guarea thompsonii), were obtained in the form of sawmill waste from Nigeria and evaluated to determine their potential for gasification. Pyrolysis and gasification kinetics of the samples were investigated using a thermogravimetric analyser (TGA) at temperatures of 900 ºC and 1,000 ºC. Four iso-conversional methods, one peak temperature method, and two model-fitting methods were employed to determine the kinetic parameters, i.e. the apparent activation energy Ea, and pre-exponential factor A. Values of the gasification kinetic rate constant K were determined using two gas-solid reaction models: the volumetric reaction model (VRM) and the shrinking core model (SCM). The values obtained for all three kinetic parameters showed good agreement with values derived for samples of non-tropical wood.

Xylan-degrading enzymes from Aspergillus niger and Hypocrea orientalis were characterized by enzyme activity assays and protein profiling with SDS-PAGE and LC-MS/MS. The hydrolysis of Miscanthus xylan by xylan-degrading enzymes from A. niger, H. orientalis, and Trichoderma reesei were comparatively studied by HPLC analysis. It was found that the glycoside hydrolase families 10 xylanase was the main xylanase secreted by H. orientalis and A. niger when using corn cob and wheat bran as inducers. Compared to the enzymes from T. reesei,the enzymes from A. niger showed better efficiency in the hydrolysis of Miscanthus xylan into monosaccharides. Nevertheless, the enzymes from H. orientalis were more preferable for the hydrolysis of Miscanthus xylan into xylo-oligosaccharides (XOS), especially xylobiose and xylotriose. Miscanthus xylan degradation was significantly influenced by the activities of β-xylosidase and α-L-arabinofuranosidase. Xylan-degrading enzymes with high ratios of β-xylosidase and α-L-arabinofuranosidase are necessary for the efficient conversion of Miscanthus xylan into monosaccharides. However, xylan-degrading enzymes with low β-xylosidase activity and high α-L-arabinofuranosidase activity were required for producing XOS.