Research Articles

There has been great attention focused on the effects of first and second generation biofuels on global warming. The Energy Independence and Security Act (EISA) and the Renewable Fuel Standard (RFS) have mandated production levels and performance criteria of biofuels in the United States. The thermochemical conversion of biomass to ethanol shows potential as a biofuel production pathway. The objective of this research was to examine the alcohol yields and GHG emissions from the thermochemical conversion process for six different feedstocks on a gate-to-gate basis. GHG analyses and life cycle assessments were performed for natural hardwood, loblolly pine, eucalyptus, miscanthus, corn stover, and switchgrass feedstocks using a NREL thermochemical model and SimaPro. Alcohol yield and GHG emission for the hybrid poplar baseline feedstock conversion were 105,400 L dry metric ton−1 and 2.8 kg CO2 eq. per liter, respectively. Compared with the baseline, loblolly pine produced the highest alcohol yields, an 8.5% increase, and the lowest GHG emissions per liter of ethanol, a 9.1% decrease. Corn stover, due to its high ash content, had the lowest yields and the highest GHG emissions per liter of ethanol. The results were highly sensitive to the ash and water content of the biomass, indicating that biomass properties can significantly affect the environmental impact of the thermochemical ethanol conversion process.

The interactive effect of the thermo-mechanical densification and heat treatment on the set-recovery of modified wood were investigated for optimizing the combined modification process in this study. Process parameters such as thermo-mechanical densification temperature, duration of densification, and heat treatment temperature were selected as main factors; three levels of each of these factors were chosen, and then nine experiments plus one verification experiment were conducted according to the principles of the Taguchi DoE method and the results of ANOVA analysis. It was observed that the dimensional stability of combined modified Chinese fir wood in the compression direction can be effectively improved by elevating the heat treatment temperature and densification temperature, the percentage contributions of which were 76.04% and 21.18%, respectively. Meanwhile the set-recovery had no dependence on the duration of the densification process. The value of the set-recovery in the verification experiment agreed quite well with the predictions. From an economic view, the optimal condition for the combination modification of Chinese fir wood was that of a densification temperature of 170 °C, densification duration of 10 min, and heat treatment temperature of 200 °C.

An oxygen-delignified eucalypt pulp (Eucalyptus grandis x Eucalyptus urophylla hybrid)was provided by a Brazilian pulp mill. It was treated with chlorite to remove lignin, or by a long acidolysis stage to remove most of the hexenuronic acid groups (HexA) followed by a chlorite treatment to remove the lignin. Three pulp samples were treated with increasing ozone charges (up to 2% on pulp) at high consistency and room temperature. The pulp containing no lignin but all of the HexA appeared to be the most affected by the ozone treatment. This indicated that the reaction of ozone with HexA generates radicals, which then react with cellulose, leading to depolymerization. It also indicated that lignin captures some of these radicals. ESR spectroscopy confirmed that hydroxyl radicals are formed when ozone reacts with maleic acid, which can be considered a HexA model compound. These findings open the way to the improvement of chlorine-free bleaching sequences containing ozone stages.

The effects of the amounts of flour from the red pepper (Capsicum annuum) fruit stem (RPFS), together with coupling agent (CA), on the mechanical and physical properties of polypropylene (PP)-based composites were investigated. Pellets manufactured through single screw extruders were injection molded into composite samples. Density, mechanical property, and dimensional stability of manufactured composites were determined according to ASTM standards. Results were analyzed using central composite design (CCD). Statistical analyses showed that filler loading significantly affected the density, as well as mechanical and physical properties of thermoplastic composites. Density of the composites was increased with filler loading but not affected by coupling agent amounts. In the case of mechanical properties, tensile modulus, flexural strength, and flexural modulus were improved with increasing filler loading while the tensile strengths, elongation at break, and impact strength of the samples were decreased. The tensile strength of the thermoplastic composites was positively affected by CA contents, but other mechanical properties were not affected as much. In the case of physical properties, thickness swelling and water absorption of the composites were increased with increasing weight percent of RPFS flour. However, these properties were not significantly changed by CA addition. Overall results revealed that RPFS flour could be potentially suitable raw materials for thermoplastic composites.

Sporisorium reilianum is a phytopathogenic fungus that produces the maize head smut. Hydrolytic enzymes such as xylanases have not been studied in this basidiomycete, although these enzymes are widely used within the industry. In this study, the characterization of a xylanase produced by S. reilianum grown in submerged and solid-state fermentation using different culture media was performed. Submerged fermentation with a medium containing birch xylan and yeast extract showed the highest xylanase activity (12.6 U/mL). The enzyme, purified through ion exchange chromatography, had a molecular weight of 42 kDa, as determined by SDS-PAGE, and a Km and Vmax of 1.72 mg/mL and 2.48 μmol/mL/min, respectively. The optimal values of pH and temperature were 5.0 and 70 °C, respectively. The enzyme showed activity over a broad range of temperatures and pHs. Zn2+, Fe3+, and Mn2+ ions increased xylanase activity. Sequence protein analysis showed 100% similarity with the theoretical protein encoded by the sr14403 gene of S. reilianum, encoding a putative endo-b-1,4-xylanase. This is the first report on the production and purification of a xylanase from this fungus, which has interesting biochemical characteristics for application in biotechnological processes.

Hemicellulose material is an abundant and relatively under-utilized hetero-polysaccharide material present in lignocellulosic materials. In this study, an alkaline treatment was applied to sweetgum and Eucalyptus globulus chips to extract hemicelluloses prior to kraft pulping to subsequently evaluate the final product and process. An alkaline extraction (10 and 50% NaOH by weight on wood) for 60 min at 100 °C followed by precipitation in ethanol recovered 4.3% of the biomass as a predominantly xylan material (sweetgum 50% NaOH) with an average degree of polymerization around 250 and functional groups similar to a commercial xylan (sweetgum 10% NaOH). This process in comparison to autohydrolysis (water extraction at 100 °C) produced a much higher molecular weight and more pure hemicellullose. The results obtained indicate a promising combination between the effective extraction of hemicellulose from wood and a distillation process that recovers the ethanol, which may be an attractive alternative to recover liquor and ethanol after hemicellulose precipitation. Hemicellulose from sweetgum showed more thermal stability with high molecular weight compared to the hemicellulose extracted from Eucalyptus globulus. An attractive alternative looks to be to recover liquor and ethanol after hemicellulose precipitation.

Alkaline precipitate isolated from red liquor of acidic magnesium sulfite pulping exhibited obvious stratification. The properties of the stratified alkaline precipitate were investigated via infrared spectroscopy, ion chromatography, thermogravimetric analysis, and high efficiency liquid chromatography. The sulfonic group of lignosulfonate showed a characteristic absorption peak from 1210 cm^-1 to 1170 cm^-1. There were no significant differences between the structures of the functional groups of the upper and lower layers of the precipitate. The peak time of the sulfonic group was 6.350 min, as measured by ion chromatography. Compared with the upper precipitate, the lower precipitate had more groups with high carbon and low oxygen contents and did not easily decompose. The relative molecular weight of the lower precipitate was greater than that of the upper precipitate. The difference in relative molecular weight of the precipitates gave rise to the observed stratification.

Water hyacinth was analyzed to determine its hemicellulose/lignin content, evaluating the conditions for the saccharification process with commercial microbial enzymes. Plant material, including leaves and stalks, was pretreated at several temperatures (100, 110, and 120 °C) with different sulfuric acid concentrations (0.5, 1.0, 1.5, 2.0, 2.5, and 3%) and residence times (0, 15, 30, 45, 60, 90, and 120 min). Total reducing sugars were measured by the dinitrosalicylic acid method. The optimum conditions that maximized the yield of reducing sugars included a pretreatment with 2% (v/v) sulfuric acid at 110 °C for 90 min. The optimum conditions for enzymatic saccharification used the commercial enzyme Celluclast at 50 °C for 24 h of hydrolysis. The maximum yield was 0.54 g of fermentable sugars per gram of biomass. Data demonstrated that E. crassipes is suitable as a raw material for products such as bioethanol; however, further fermentation studies are required.

The vibrational properties of Japanese cedar wood at high temperature were measured. The specimen, its support system, a magnetic driver, and a deflection sensor were placed in an electric drying oven, where vibration tests were conducted. The heating temperatures ranged from 25 ºC to 200 ºC in 25 ºC increments. The resonance frequency decreased with higher heating temperature and decreased most dramatically in the temperature range of 150 ºC to 200 ºC. The loss tangent had a minimum value at 100 ºC and changed more in the temperature range from 150 ºC to 200 ºC than in the range from 25 ºC to 150 ºC. The changes in the resonance frequency and loss tangent of the specimens with larger distance from the pith (d) were smaller than those around the pith. These tendencies are believed to have occurred because the portion with a larger d had a smaller number of intercellular layers than the portion around the pith.

A biodegradable planting container made with rice straw and starch adhesives modified by polyvinyl alcohol was studied in this paper. The effect of heat treatment and polyamide resin on the properties of planting containers was investigated. The physical property and biodegradibility were characterized by means of hygroscopicity, FTIR, degradability, and the thermogravimetric analysis. The results showed that the dry strength of planting containers increased as a result of both treatments. The wet strength of planting containers increased as a result of heat treatment, while the wet strength of planting containers decreased as a result of polyamide resin. The hygroscopicity of planting containers decreased with heat treatment and polyamide resin. The effect of heat treatment was more obvious than the effect of polyamide resin. It was observed that the peak intensity and position were changed for the 3400 cm^-1, 2900 cm^-1, 1640 cm^-1, 1500 cm^-1, 1400 cm^-1, and 1050 cm^-1 under the treatment of polyamide resin. The weight loss of specimens treated with polyamide resin was larger because of the presence of nitrogen in the resin. The appearance of planting containers showed the heat treatment containers were not easily prone to mildew when used for planting. The thermogravimetric analysis (TGA) showed that heat treatment can improve the thermal stability, while the polyamide resin was shown to promote the degradation of planting containers.