Volume 14 Issue 3

The large amount of cellulose found in Ulva sp. and its low percentage of lignin-like compounds make it an interesting raw material for partially substituting wood pulp to produce pulp and paper. This work shows the suitability of mild chemical treatments for papermaking using residual biomass from this green seaweed, harvested on the beaches, in order to give it added value. A chemical characterization was used to determine ethanol-benzene, hot water, and 1% soda extractives, ash content, holocellulose, α-cellulose, and acid-insoluble material. Cellulose extraction was performed with low proportions of soda and hydrogen peroxide, and it was subjected to a refining step. A design of experiments was used to explain the influence of soda (6%, 8%, and 10%) and hydrogen peroxide (2%, 4%, and 6%) based on oven-dry weight, plus refining (1000 PFI revolutions, 3000 PFI revolutions, and 5000 PFI revolutions). The results showed that to attain good paper strength, it is advisable to operate at maximum alkali charge, minimum peroxide concentration, and refine to a high degree.

The characterization of tamarind shell tannins for potential use in rust transformation was studied. Fourier-transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), and phytochemical assays were applied to examine tamarind shell tannins. The analyses revealed that the methanol extract of tamarind shell (TME) was rich in phytochemical compounds, compared to that of aqueous acetone extract of tamarind shell (TAE). Furthermore, the FTIR and NMR studies confirmed the presence of tannins. The FTIR study on the performance of tamarind shell tannins on rust treatment via the effects of concentration, pH, and reaction time was evaluated. The FTIR spectra revealed that the percentage rust transformation (RT %) was in the order of lepidocrocite (γ-FeOOH) > magnetite (Fe3O4) > goethite (α-FeOOH). Meanwhile, the results obtained revealed that lepidocrocite peaks completely disappeared, and magnetite peaks reduced intensity up to 95.83 RT % for TME and 94.75 RT % for TAE. The TME was the best rust converter at 7% concentration.

Wood thermal modification is an environmentally friendly method used to improve wood characteristics, and its degradation mechanism directly influences its application in construction, building, and home decoration. Combined thermogravimetry and Fourier transform infrared (TG–FTIR) studies were conducted to evaluate the hardwood and softwood on-site at 160 °C and 220 °C. The results indicated that the mass loss rates (MLRs) for both hardwood and softwood samples decreased over time and ultimately became constant. The total mass loss increased with an increase in temperature. The total mass loss was about 3% at 160 °C, and about 4.7% to 6.5% at 220 °C. Decomposition also occurred much more easily in the hardwood than in the softwood. More species of gas products were emitted from hardwood than softwood, and the number of species of gas products increased with an increase in temperature and processing time. The FTIR spectra of softwood were similar, whereas those of hardwood were remarkably different at different temperatures. Water and alcohol were generated from both the hardwood and softwood, whereas contents of these gaseous products were visible in hardwood decomposed at 220 °C during the thermal treatment. Ketones, ethers, acids, and aromatics were found in both hardwood and softwood, whereas CO2 was only found in the hardwood that underwent thermal treatment.

Cassava stem was bioconverted to ethanol using microorganisms. First, cassava stem was pretreated by in ways, alkaline solution alone (ASA), microwave treatment combined with alkaline solution (MTCAS), and ultrasonic treatment combined with alkaline solution (UTCAS). The compositions of cassava stem pretreated by different methods were analyzed, and the results showed that the cassava stem pretreated by MTCAS was more suitable for saccharification and subsequent ethanol production. The pretreated cassava stem was subjected to simultaneous saccharification and ethanol production using Aspergillus fumigatus and Saccharomyces cerevisiae. Response surface methodology was used to optimize various process parameters including fermentation temperature, initial pH, fermentation time, rotational speed and substrate concentration. A bioconversion yield of 70 mg/g was obtained at the optimum conditions of fermentation, viz, temperature 35 °C, initial pH 5.6, fermentation time 132 h, rotational speed 155 rpm, and substrate concentration 4.6 wt%. An experiment under optimum conditions confirmed the model predictions. The results suggest that pretreatment with MTCAS and simultaneous fermentation with A. fumigatus and S. cerevisiae would be a good choice for the bioconversion of lignocellulosic biomass to bioethanol. Considering the cost advantage, using microbial fermentation instead of pure enzyme hydrolysis is more advantageous in 2nd generation bioethanol production.

The behavior of three hardwood species was investigated in response to natural and artificial light irradiation. The effects of irradiation were evaluated by their color measurement in the CIELab system and Fourier-transform infrared (FTIR) spectra. Both natural light irradiation and artificial light irradiation induced changes in color, such as yellowing and darkening, in the wood species. Comparative in-time evolution of changes in color during artificial light irradiation and natural light irradiation under indoor conditions resulted in an estimated acceleration index that ranged from 60× to 90×.The FTIR spectra highlighted specific changes in surface chemistry during irradiation. Ultraviolet light from natural or artificial sources primarily resulted in lignin degradation.

Two runs of commercial-scale radio-frequency/vacuum (RF/V) drying for maple hardwood were performed to explore the practical technology and its drying characteristics. The results revealed that the power density was a prerequisite for the drying schedule development. The drying time and in-process moisture content (MC) were evaluated by the calculated amount of dehydration at 1% MC removal. The drying defects, such as checks, bowing, and twist, and MC variation met the requirements of GB/T 6491 (2012). The drying rate of run 2 increased 22% after the drying schedule modification. The dehydration capacity was affected by the temperature, which first increased fast as the wood temperature increased to the boiling point and then increased more slowly after that point. The dehydration capacity was also associated with the initial lumber MC. Approximately 30% of the total energy maintained the chamber vacuum and approximately 70% was used for RF heating for both runs. The overall specific energy for water removal during RF/V drying had a competitive advantage compared with conventional kiln drying. The energy conversion efficiency of both runs was low at 50% during the warming stage, and increased to 80% and 90% for Run 1 and Run 2, respectively, during the drying stage.

Nanocellulose made by 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-catalyzed oxidation, described as TEMPO-oxidized cellulose nanofibers (TOCNs), has a high density of negative charges on its surface. Its use in microbial fermentation systems is expected to benefit microbial process stability. In particular, microbial stability is strongly required in acetone–butanol–ethanol (ABE) fermentation associated with the solvent-extraction process of butanol production. Here, TOCNs derived from oil palm empty fruit bunches pulp were added to extractive ABE fermentation media containing glucose as a main source, which can be potentially obtained from biomass by saccharification. Then, microbial fermentation was carried out using free or immobilized bacterial cells, to produce butanol from glucose. The presence of TOCNs induced higher total butanol production in broth by improving the growth environment of Clostridium saccharoperbutylacetonicum N1-4, which was used as the butanol-producing strain. Microscopic analysis revealed that the spider-web-like TOCN network helped to entrap bacterial cells in alginate beads, by ionic crosslinking of TOCNs and alginates via Ca2+ ions, to increase stability of bacterial cells in the composite gel beads. The addition of TOCNs to fermentation media had significant positive effects on the total butanol yield.

Pretreatment of steam-exploded wheat straw by ethanol has been used to dissolve lignin. Different pretreatment conditions were explored by varying reaction temperature, time, and the ratio of solid to liquid to determine that the rate of dissolution was approximately 51.6%. The examination of structural changes in LP (lignin from ethanol pretreatment pulp) showed that the conjugated carbonyl/carboxyl of lignin was partly destroyed during ethanol pretreatment and alkali extraction process. The content of total hydroxyl groups was increased with increasing ethanol pretreatment. Higher intensities of the aromatic ring in LP and LL (lignin from black liquor) fractions compared to that of weak pretreatment conditions indicated that some extent of lignin condensation occurred during the ethanol pretreatment. The ratios of S/G in LP were higher than in LL and removal of the methoxyl groups happened during the ethanol pretreatment process, and this led to changes in proportions of lignin structural units.

Due to the huge demand for as well as the limited reserves of fossil resources, renewable biomass that can be converted into chemicals has become a global research focus. In this paper, cornstalk residue was liquefied using a mixture of polyethylene glycol with a molecular weight of 400 g/mol (PEG400) and ethylene carbonate (EC) as the liquefaction reagent and 5-sulfosalicylic acid (SSA) as the catalyst. The liquefaction product of the cornstalk residue (CRL) was used to replace petroleum polyols to prepare flexible polyurethane foams. The results showed that the optimum liquefaction conditions were as follows: PEG400/EC was 7.5:2.5 (w/w), the ratio of liquid/solid was 5:1 (w/w), the liquefaction temperature was 160 C, the mass of SSA was 4 g, and the liquefaction time was 60 min. The hydroxyl number and residue content of the CRL at optimal conditions were 315.7 mg KOH/g and 4.5%, respectively. The compressive strength and apparent density of the polyurethane foam, which was prepared by 90 wt% CRL, 10 wt% commercial polyether GE-220, and methylene diphenyl diisocyanate, were 205.6 kPa and 0.075 g/cm3, respectively.

The catalytic pyrolysis of rice straw for syngas (H2 + CO) production with nickel oxide (NiO)/fly ash catalysts was investigated in a horizontal fixed-bed quartz tube reactor. Besides, X-ray diffraction, X-ray fluorescence, field emission scanning electron microscopy, and Brunauer-Emmett-Teller analysis were employed to study the physiochemical properties of the catalysts before and after catalytic pyrolysis of biomass. The results illustrated that NiO was uniformly loaded on the surface of fly ash via a filament-like coating. Furthermore, the effects of calcination temperature (400 to 700 °C), reaction temperature (550 to 800 °C), holding time (5 to 35 min), and NiO loading (5 to 30 wt%) on the catalyst performance were investigated. Analysis of the gas composition showed that the NiO/fly ash catalyst had the best ability to increase H2 and CO concentration at a 400 °C calcination temperature, 600 °C reaction temperature, 20 wt% NiO loading, and 20 min holding time. Compared with rice straw pyrolysis alone at these conditions, the concentration of H2 and CO experienced a steep increase from 7 vol% to 41 vol% and 18 vol% to 34 vol%, respectively. The catalyst developed in this research opens a new pathway for the utilization of fly ash in the field of biomass pyrolysis.