Journal of Lignocellulose
Volume:1 Issue: 3, 2012

Rising paper consumption due to growth of the world’s population along with enlarging diversity of paper applications are putting more harvesting pressure on limited natural resources of the planet. Moreover, efforts to reduce papermaking effluents and the disposal of waste paper as a solid waste material are causing other environmental concerns. Paper recycling can reduce the volume of solid wastes while producing a main product with less raw material and energy costs. In this respect, to achieve a great recycling performance, the roles of an effective waste paper collect/bring system, governmental support and publicity for recycling should not be neglected. On the other hand, extensive research and technical progresses have helped to overcome some problems encountered with the recycled paper quality. Consequently, paper industry can rely more on an effective solution as recycling.

In this research, the effect of microwave radiation and steaming pretreatments on drying rate and residual stresses of fir wood (Abies alba L.) was investigated. Wood samples with green dimensions of 340 × 100 × 50 mm and initial moisture content of about 50% were exposed to either steam or microwave radiation treatment before being conventionally dried. The pre-steaming was performed at temperatures of 120, 140, and 160°C for 1 hour, and the microwave treatment was applied with 2.45GHz frequency for 7 and 10 minutes at three different conditions. Results revealed that the pre-steaming at 140 and 160°C and the microwave radiation for 10 minutes imposed greater effect on the drying rate. The residual drying stresses were reduced due to the microwave radiation; in contrast, they were increased as a result of steaming at 140 and 160°C.

The effects of chemical composition of various wood species and resin type on the dimensional stability, mechanical properties, and formaldehyde emission of particleboard were investigated. The solubility in cold and hot water, NaOH, and alcohol-benzene were evaluated, as well as the amount of cellulose, α- cellulose, holocellulose,hemicelluloses, and lignin and the acidity (pH) of the wood particles after the chipping process. The chemical compositions of wood and resin type were the main parameters influencing physical properties, mechanical properties, and formaldehyde emission of particleboard. While high cellulose and α-cellulose content resulted in superior mechanical properties, high hemicelluloses content was detrimental to the mechanical properties and dimensional stability. The extractives dissolving in cold and hot water decreased the formaldehyde emission of particleboard. Hemicelluloses were found to be effective at lowering formaldehyde emission. High hemicelluloses content caused lower formaldehyde releasing. Extractives dissolving in the NaOH and alcoholbenzene positively affected the dimensional stability of particleboard panels. Resin type was found to have an effect on all of the properties of particleboard. Particleboards produced with melamine-urea formaldehyde resin showed better quality properties and lower formaldehyde emission compared to the particleboards produced with urea-formaldehyde resin.

The cellulose microfibrils (CMF) from natural lignocellulosics are newly understood and exciting biomaterial constituent that can provide strong reinforcement in many products, including polymer composites. In this study, the cellulose crystals were extracted from jute and bagasse fibers based on the formic acid/ peroxyformic acid/peroxide process at atmospheric pressure, and their yields were 59.8 and 38.1%, respectively. Considering the biorefinery concept, the dissolved lignin and hemicelluloses in the processes were also isolated from the spent formic acid liquor. The results showed that the spent liquor contained 10.6 and 28.2% (on oven dried raw material) total sugars, and 10.9 and 16.9% lignin for jute and bagasse fibers, respectively. The xylose was the dominant sugar in the spent liquor. The cellulose microfibrils were further prepared from the extracted cellulose based on the acid hydrolysis technique. A very high yield of cellulose microfibrils (48.0 % based on the jute raw material) was obtained from jute fibers, while only 18.2% yield was obtained from the bagasse. The acid hydrolysate of jute cellulose contained 5.52% sugar, while bagasse hydrolysate contained 17.71% of sugars. The CMF samples obtained from the two different raw materials were characterized by means of TGA, FTIR, XRD, and TEM techniques. The average diameter of the CMF was 15-40 nm. The XRD results revealed that both CMF had a high crystallinity index. The thermal stability of MCC/NCC from the jute fibers was higher than that from the bagasse.

A locally isolated strain of Bacillus subtilis NS7 was found to produce xylanase-cellulase complex in submerged-state fermentation. A nutrient broth supplemented with xylan, soybean meal, NaCl, and KH2PO4 produced the highest enzyme yields after 72 h of incubation at 37 °C and pH 6.5, revealing xylanase, CMCase, and FPase activities of 353 IU/ml, 1.90 IU/ml, and 1.8 IU/ml, respectively. The enzyme mixture had compatible pH and temperature optima of 6.5-7.0 and 50-55 °C, respectively. The enzyme components were active over a broader range of pH (5.0-9.0) and temperature (40-70 °C). The enzymes appeared to be metalloproteins and could effectively hydrolyze various delignified agro-waste residues into reducing sugars.

Pycnoporus sanguineus is a white rot fungus that is known for selective and destructive wood bio delignification in tropical forests. This filamentous fungus is harvested on oil palm biomass (OPB) under solid substrate fermentation (SSF) and produces white-rot decay by generating ligninolytic enzyme Laccase (Lac). Laccase is produced at room temperature in the presence of Kirk’smedia supplemented with glucose, ammonium nitrate and corn steep liquor. The Lac enzymes are able to endure temperatures ranging from 10 to 700C and also the pH variation from 2.5-6. The synthesis of this enzyme, accountable for lignin degradation in oil palm biomass can further be exploited to degrade the unmanageable organic contaminants in the atmosphere. It is observed that selective lignin degradation was produced by P.sanguineus for time period of 4 weeks. The weight and component losses of oil palm trunk chips after decay were evaluated and analyzed by Scanning Electron Microscope. The maximum Laccase activity was 1007. 8 U/L on the 10th day of incubation. The present work is dedicated to assess the biodegradation of oil palm biomass and study for its pretreatment of enzyme activity.

Unbleached kraft pulp from Eucalyptus camaldulensis with an initial kappa number of about 31 and brightness of 13% was used to perform bleaching experiments. The results of the first part of this research (using D0ED1 bleaching sequence at different kappa factors of 0.2, 0.3, and 0.4 in D0 stage) showed that the final brightness, even at a kappa factor of 0.4, was relatively low (about 75%). Thus, the effects of acid pretreatment (A stage) and peroxide reinforcement in alkaline extraction (EP versus E stage) in D0ED1 bleaching sequence on optical and strength properties of paper were investigated in this study. By applying these treatments, especially peroxide reinforcement, final kappa number, yield, yellowness, opacity, and air resistance were reduced, while brightness and lightness were increased at similar or superior strength properties in comparison with the reference bleaching sequence.

Five different talc fillers with various particle size distributions (PSD) and platy shapes were evaluated in papermaking along with two calcium carbonate fillers, viz.: ground calcium carbonate (GCC) and precipitated calcium carbonate (PCC). The GCC was the finest filler with a rhombohedral shape, while the PCC was coarser than GCC with a scalenohedral shape. The cationic and anionic polyacrylamide retention aids were used with talc and calcium carbonate fillers, respectively, to retain them within paper matrix. The laboratory handsheets were prepared from all fillers with the target ash in paper ranging from 14 to 24%. The effect of talc particle size and increasing ash on the optical and the structural properties of paper has been studied and has been compared with the reference calcium carbonate fillers. The optical properties of paper were improved, whereas ash retention was reduced with the finer talc filler. The retention of talc filler was the highest followed by PCC and GCC. The bulk, light scattering, opacity, porosity and roughness of paper with talc filler were the lowest, while those with PCC were the highest among all fillers.