Volume 11 Issue 3

A mathematical description was developed for production of saccharides and fermentation inhibitors during the hot-compressed water pretreatment of cassava residue. Pretreatment was conducted at 150 °C, 160 °C, 170 °C, and 180 °C, and reaction times ranged from 0 to 70 min. The formation of saccharides and four main inhibitors (furfural (F), hydroxymethylfurfural (HMF), acetic acid, and formic acid) were studied. A model for predicting the concentrations of F and HMF (CF and CHMF, respectively) as functions of H+ concentration was established. Furthermore, kinetic models were built after introducing the hydrogen ion concentration index mi. Hydrogen ion concentration had a dramatic effect on the dissolution of pentosan but did not greatly affect the dissolution of hexosan or the degradation of hexose or pentose. Additionally, the activation energies for the formation of pentose or hexose were lower than the degradation energies. The coefficients of determination (R2) of the kinetic models for predicting the yield of the four compounds (pentose, hexose, furfural, and HMF) were higher than 0.923. These kinetic models provided a theoretical foundation and technical support for controlling the production of the main carbohydrates and fermentation inhibitors.

This study describes the properties of thermoplastic polymer composites based on polyethylene (of low and high density) and ethylene-propylene copolymers using various types of conifer needles (pine, spruce, fir, and cedar) as fillers. For the needles, thermogravimetric analysis (TGA) and TGA/Fourier transform infrared spectroscopy (TGA/FTIR) were performed to investigate their structures and thermal resistance, as required for the composite processing methods. Moreover, structural differences were studied for the analyzed fillers and composite materials (FTIR). The results were compared with the values obtained for composites with conifer wood flour. Composites with conifer needles (pine) had increased water absorption and similar strength properties. However, irrespective of the degree of filling, composites with pine needles were positively characterized by the highest melt mass flow rate (MFR) values and showed a slightly better impact resistance than composites filled with other flours. Thus, shredded coniferous needles with sufficient thermal resistance could be successfully used as fillers in composites. This conclusion was based on thermoplastic polymers as an alternative and/or supplement to the wood flour used in the manufacture of wood-polymer composites.

Well-crystallized and hexagonal wurtzite ZnO was synthesized with nanocellulose using a facile hydrothermal method. Many highly active (001) facets were retained in the obtained ZnO nanocrystals, presumably due to interaction between the polar facet of ZnO and the nanocellulose. Given its effective surface area, the synthesized ZnO exhibited good photocatalytic activity of degrading methylene blue. Its degradation efficiency reached 94.4% within 30 min (UV irradiation power of 6 W), which was 34% higher than that of Degussa TiO2 P25. The ZnO photocatalyst also exhibited excellent reusability, confirmed by no obvious abatement after its being re-used for 8 cycles. These ZnO nanomaterials were synthesized using renewable nanocellulose derived from cotton. This environmentally friendly and cost-effective approach is anticipated to be applied in the future synthesis of small-sized ZnO photocatalysts.

To illuminate changes in the thermal stability of lignocellulosic biomass by homogeneous chemical modification in ionic liquids, sugarcane bagasse derivatives bearing carboxyl groups were prepared in ionic liquids. Fourier transform infrared (FT-IR) spectroscopy and solid-state nuclear magnetic resonance (NMR) confirmed the chemical structure of the derivatives. Sugarcane bagasse derivatives with degree of substituted OH as high as 9.93 mmol/g were achieved. The homogeneous esterification was demonstrated to be a more efficient approach than heterogeneous ones. Based on thermogravimetric analysis, the onset degradation temperature of sugarcane bagasse decreased dramatically to 185 °C, 160 °C and 140 °C, using succinic anhydride, maleic anhydride, and phthalic anhydride as reagent, respectively. A first-order degradation kinetic model was applied to obtain the degradation activation energies of sugarcane bagasse. The results showed that homogeneous chemical modification significantly decreased the thermal stability of sugarcane bagasse by reducing the onset degradation temperature and degradation activation energies.

In South Africa, approximately 3 × 106 tons of sugarcane bagasse is produced annually by 14 factories located on the north coast of KwaZulu-Natal. It is one of the most readily available lignocellulosic materials for ethanol production through enzymatic saccharification and hydrolysis. Pre-treatment enables disruption of the naturally resistant structure of lignocellulosic biomass to make the cellulose accessible to hydrolysis for conversion to biofuels. In this study, pre-treatment of depithed bagasse and mill-run bagasse was done using acid (3% H2SO4 v/v) followed by alkali (4% NaOH w/v), and the pre-treated solid was subjected to enzymatic hydrolysis. The effects of different conditions for enzymatic saccharification such as enzyme dose, reaction time, and amount of surfactant were studied in detail. The pre-treated substrate (10% w/v) when hydrolysed using 30 FPU/gds/40 FPU/g dry substrate (gds) with 0.4% (v/v) Tween® 80 for 20 h resulted in 608 mg/gds (depithed bagasse) and 604 mg/gds (mill-run bagasse) total reducing sugars.

Torrefaction is an important biomass pretreatment method that impacts fuel characteristics of biomass, specifically during the torrefaction process. Besides improving the fuel characteristics of biomass, torrefaction also contributes to increased quality of liquid and gaseous energy carriers obtained from fast pyrolysis and gasification. In this study, the effect of torrefaction on the solid energy carrier biochar, produced by carbonization, was studied by using solid olive mill residue (SOMR) as raw biomass. The carbonization characteristics of SOMR and torrefied SOMR (tSOMR) were compared by using ultimate and proximate analysis results. The higher heating value (HHV) and energy yields of biochars produced from SOMR and tSOMR were compared. The results showed that torrefaction contributed to the reduction of energy given to the biomass during the carbonization process by decreasing the holding time.