Comparison between two different pretreatment technologies of rice straw fibers prior to fiberboard manufacturing: Twin-screw extrusion and digestion plus defibration

The present work compares two different pretreatment technologies, i.e. twin-screw extrusion, and steaming digestion plus defibration, for producing a thermo-mechanical pulp from rice straw for fiberboard manufacturing. Five liquid/solid ratios from 0.43 to 1.02 were tested for twin-screw extrusion pretreatment, while liquid/solid ratios from 4 to 6 were used for digestion pretreatment. Energy consumption, and characteristics of the extrudates (twin-screw extrusion) and pulps (digestion) (including fiber morphology, chemical composition, thermal properties, apparent and tapped densities, as well as color) were the analyzed parameters for the resulting lignocellulosic fibers. The results showed that liquid/solid ratio had influence on energy consumption of the equipment for both defibrating methods For the twin-screw extrusion method, a lower liquid/solid ratio required more energy while for the digestion plus defibration the effect was the opposite. The corresponding total specific energy consumption ranged from 0.668 kW h/kg to 0.946 kW h/kg dry matter for twin-screw extrusion, and from 6.176 kW h/kg to 8.52 kW h/kg dry matter for digestion plus defibration. Thus, the pulping method consumed about nine times more energy than that of the twin-screw extrusion. In addition, for twin-screw extrusion, the liquid/solid ratio did not have a substantial effect on fiber characteristics with similar chemical compositions and thermal properties. For twin-screw extrusion, the energy consumption was 37% reduced when the liquid/solid ratio was increased from 0.43 to 1.02. Instead, for digestion plus defibration, the energy increase was 38% when the liquid/solid ratio increased from 4 to 6

Production of fiberboard from rice straw thermomechanical extrudates by thermopressing : influence of fiber morphology, water and lignin content

The objective of this study was to investigate the influence of fiber morphology and molding parameters on the mechanical and physical properties of fiberboards made from rice straw. The rice straw was thermomechanically treated with a twin-screw extruder. Three parameters were investigated: the amount of water added at molding (0–20%), lignin content (0–25%), and the liquid/solid ratio used for extrudate production (0.33–1.07). A Doehlert experimental design was used to evaluate the effects of these factors on fiberboard properties. A liquid/solid ratio of 0.4 at extrudate production, the addition of 5% water at molding, and a lignin content of 8.9% were found to be optimal for bending properties. The fiberboard produced in these conditions had a density of 1414 kg/m3 (i.e. the densest board). Maximum flexural strength and elastic modulus were 50.3 MPa and 8.6 GPa, respectively. A thickness swelling of 23.6% and 17.6% water absorption were observed. The statistical analysis suggested that a good compromise between density and flexural properties could be obtained with the addition of 0% water, a lignin content of 25% and a liquid/solid ratio of 0.33 at extrudate production. Polynomial models suggested that the fiberboards produced in such conditions would have a maximum flexural strength of 50 MPa, an elastic modulus of 6.0 GPa, a density of 1102 kg/m3, and a thickness swelling of 24%

Land Use and Land Cover Changes and Its Impact on Soil Erosion in Stung Sangkae Catchment of Cambodia

Agricultural expansion and urban development without proper soil erosion control measures have become major environmental problems in Cambodia. Due to a high population growth rate and increased economic activities, land use and land cover (LULC) changes will cause environmental disturbances, particularly soil erosion. This research aimed to estimate total amounts of soil loss using the Revised Universal Soil Loss Equation (RUSLE) model within a Geographic Information System (GIS) environment. LULC maps of Japan International Cooperation Agency (JICA) 2002 and Mekong River Commission (MRC) 2015 were used to evaluate the impact of LULC on soil erosion loss in Stung Sangkae catchment. LULC dynamics for the study periods in Stung Sangkae catchment showed that the catchment experienced a rapid conversion of forests to paddy rice fields and other croplands. The results indicated that the average soil loss from the catchment was 3.1 and 7.6 t/ha/y for the 2002 and 2015 periods, respectively. The estimated total soil loss in the 2002 and 2015 periods was 1.9 million t/y and 4.5 million t/y, respectively. The soil erosion was accelerated by steep slopes combined with the high velocity and erosivity of stormwater runoff. The spatial distribution of soil loss showed that the highest value (14.3 to 62.9 t/ha/y) was recorded in the central, southwestern and upland parts of the catchment. It is recommended that priority should be given to erosion hot spot areas, and appropriate soil and water conservation practices should be adopted to restore degraded lands

Production of fiberboard from rice straw thermomechanical extrudates by thermopressing: influence of fiber morphology, water and lignin content

The objective of this study was to investigate the influence of fiber morphology and molding parameters on the mechanical and physical properties of fiberboards made from rice straw. The rice straw was thermomechanically treated with a twinscrew extruder. Three parameters were investigated: the amount of water added at molding (0-20%), lignin content (0-25%), and the liquid/solid ratio used for extrudate production (0.33-1.07). A Doehlert experimental design was used to evaluate the effects of these factors on fiberboard properties. A liquid/solid ratio of 0.4 at extrudate production, the addition of 5% water at molding, and a lignin content of 8.9% were found to be optimal for bending properties. The fiberboard produced in these conditions had a density of 1414 kg/m3 (i.e. the densest board). Maximum flexural strength and elastic modulus were 50.3 MPa and 8.6 GPa, respectively. A thickness swelling of 23.6% and 17.6% water absorption were observed. The statistical analysis suggested that a good compromise between density and flexural properties could be obtained with the addition of 0% water, a lignin content of 25% and a liquid/solid ratio of 0.33 at extrudate production. Polynomial models suggested that the fiberboards produced in such conditions would have a maximum flexural strength of 50 MPa, an elastic modulus of 6.0 GPa, a density of 1102 kg/m3 , and a thickness swelling of 24

Fiberboards Made from Corn Stalk Thermomechanical Pulp and Kraft Lignin as a Green Adhesive

The feasibility of incorporating purified kraft lignin, at different concentrations ranging from 5 to 29%, into fiberboards made from corn residues was studied. The lignin was obtained from black liquor, which is a residue of the paper industry. Corn stalk raw material and its thermomechanically produced fiber were characterized in terms of their chemical composition. The physical and mechanical properties of the resulting fiberboards were evaluated. The fiberboards produced following a wet process had good mechanical and water resistance properties that satisfied the requirements of the relevant standards. In addition, a Life Cycle Thinking (LCT) approach suggested that lignin-based fiberboards are environmentally preferable than those based on thermosetting resins

Fiberboards Made from Corn Stalk Thermomechanical Pulp and Kraft Lignin as a Green Adhesive

The feasibility of incorporating purified kraft lignin, at different concentrations ranging from 5 to 29%, into fiberboards made from corn residues was studied. The lignin was obtained from black liquor, which is a residue of the paper industry. Corn stalk raw material and its thermomechanically produced fiber were characterized in terms of their chemical composition. The physical and mechanical properties of the resulting fiberboards were evaluated. The fiberboards produced following a wet process had good mechanical and water resistance properties that satisfied the requirements of the relevant standards. In addition, a Life Cycle Thinking (LCT) approach suggested that lignin-based fiberboards are environmentally preferable than those based on thermosetting resin