Volume 11 Issue 3

As expressed by the chorus lyrics of a song by Dan Einbender, “it really isn’t garbage ‘til you mix it all together. It really isn’t garbage ‘til you throw it away. Separate your paper, plastic, compost, glass and metal. Then you get to use it all another day.” It’s worth paying attention to these lyrics once again in the face of yet another type of product that is starting to show up in stores. Extruded sheets of polyethylene (no. 2 plastic) with as much as 80% ground calcium carbonate content are being sold as “paper”. Calcium carbonate is widely used as a component of real paper. However, it rubs me the wrong way when the word “paper” is being used to refer to something that has no fibers in it and is not formed on a screen and dried. My more serious concern is that such materials, if they become widely used, have the potential to contaminate paper recycling operations.

It is never too late or too early to invent alternative processes for the betterment of our routine life. For paper production, trees are being cut in huge quantities each day, and this directly affects our day to day life by making atmospheric conditions less favorable. Waste paper can be recycled on average 4 to 6 times while maintaining acceptable qualities in recycled paper. To save forest resources, we should move ahead towards using more and more waste paper for paper production. A wasted resource can be recycled either to make the same product or by manufacturing new products, e.g. cardboard boxes, newspaper, writing and printing papers, and paper bags, etc. Several waste paper grades are not being fully utilized, and their use might allow increased paper recycling to produce new recovered paper with specified paper qualities. Polycup stock is an example of an under-utilized type of wastepaper that has the potential to substitute effectively for virgin pulp production.

The use of supercritical water for the decomposition of lignin and evaluation of its influence on lignin decomposition and conversion to various products was the thrust of the current study. Poplar alkali lignin (AL), corncob-to-xylitol residue lignin (XRL), and cornstalk-to-ethanol residue lignin (ERL) were the lignin species studied because they constitute the main residual lignins available in the biomass refinery industry. The lignins were characterized by elementary analysis, Fourier transform infrared spectrometry (FT-IR), phosphorus nuclear magnetic resonance (31P-NMR), and X-ray diffraction (XRD), and their hydrothermal depolymerization products were analyzed by gas chromatography-mass spectrometer (GC–MS). The results showed that the residual lignin is a potential source for valuable aromatics. The XRL had the best total phenolics yield, 140 mg/g, while AL had the lowest, 90 mg/g. The maximum yields of phenol (28.94 mg/g) and 4-ethylphenol (36.21 mg/g) were obtained from XRL depolymerization at 375 °C for 30 min, and the optimal yields of guaiacol (14.34 mg/g) and 2,6-dimethoxyphenol (15.67 mg/g) were achieved by AL at 375 °C for 30 min. The information here provides some insights toward developing selective biorefinery methods for lignin-to-organic products conversion processes.

Maximizing the amount of monomeric sugar yield from lignocellulosic materials requires an effective pretreatment process and identification of an optimal enzyme loading for cost-effectiveness. In this work, a microwave-diluted sulfuric acid pretreatment was applied prior to enzymatic hydrolysis of sago palm bark (SPB). Characterization of the solid fraction was completed before and after the pretreatment process. Analysis of SPB ash showed a presence of 6.8% silica. There was a 32% reduction in lignin content, an increased crystallinity from 29% to 47%, and clear damage and fragmentation to the surface structure of SPB after the pretreatment. Inhibitors were not detectable in the liquor after the microwave-acid pretreatment. The enzymatic hydrolysis of SPB was employed by adding 6 to 42 FPU/g of cellulase and 50 U/g of β-glucosidase to identify the optimal cellulase loading at fixed β-glucosidase loading. The maximum total monomeric sugar yield and total reducing sugar (using DNS method) at 77 mg/g and 378 mg/g were achieved using 24 FPU/g of cellulose, respectively. Thus, this enzyme loading can be recommended for further microwave-acid pretreatment and enzymatic hydrolysis of SPB.

Principles and methods to dynamically test the Poisson’s ratio of isotropic material and timber are proposed in this work. Five species of lumbers were processed into cantilever plates of tangential, radial, and cross sections with different length-width ratios of 6, 5, 4, and 3. The “Shell 63” element in ANSYS software was adopted to calculate strain and stress under the first-order bending mode. The paste position of the strain rosette for the Poisson’s ratio of timber was obtained through strain-stress relationship and regression analysis under states of stress, strain analysis, and plane stress. This method was also applied to steel, aluminum, and glass. For both isotropic and orthotropic materials such as timber, the paste positions of the strain rosette were determined by the position where transverse stress within the plate was zero during the first-order bending vibration. Meanwhile, the lateral and longitudinal strains of the spectrum were measured using the transient excitation method. In the spectrum, the ratio of linear amplitude between the lateral and longitudinal strain of the first-order bending frequency was taken as the measured value of the Poisson’s ratio of the material. The accuracy of the results was verified by axial tension and static four-point bending tests.

A series of acid hydrolysis lignin-g-poly-(acrylic acid) (AHL-g-PAA) composites was prepared by grafting acid hydrolysis lignin on the surface of the polyacrylic acid network. The results of structure analysis revealed that AHL-g-PAA had been grafted. The surface morphologies of the hydrogels were improved, as shown by scanning electron microscopy observation. The AHL-g-PAA hydrogel had high water absorption and it possessed sensitivity to external pH stimulus. This study also revealed that the adsorption capacity of AHL-g-PAA was 235 mg/g for Pb(II) ions. The adsorption kinetics data could be described by the pseudo-second-order model, and the adsorption isotherm agrees well with the Langmuir model.

The effects of vacuum heat treatment were studied relative to the chemical composition of larch wood. The samples were heat-treated in vacuum at 160 °C, 200 °C, and 240 °C for 4 h, and the chemical changes were investigated by wet chemical analysis, elemental analysis, calorific value determination, and pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS). The relative percentage contents of lignin and extractives increased after heat treatment. Additionally, the relative percentage contents of holocellulose, cellulose, and hemicelluloses decreased as a result of the thermo-vacuum treatment. Elemental analysis showed a slight reduction in the contents of hydrogen and oxygen. Vacuum heat treatment also increased the calorific value compared with untreated samples.