Potential of some Latvian Industrial Crops Residuals for Conversion to Bio-Based Thermal Insulation Material

Abstract

Some industrial crops residuals like wheat straw, buckwheat husks and reeds were used in the study as raw lignocellulosic materials to evaluate their potential as thermal insulation material. Steam explosion (SE) pre-treatment was used to disrupt and convert the raw material smooth shape to foamy fibrous shape. Two level Factorial design was used to evaluate the impact of raw material fraction size (10-20-30 mm), moisture content (10-30-50%), SE temperature (200-215-230 °C) and duration (00-30-60 s) on bulk density and thermal conductivity of the obtained loose-fill materials. The results show that all selected raw materials could be characterized as thermal insulation materials as the determined thermal conductivity was in the range of 0.042–0.058 W (m K)-1 including neat samples. In spite of effective fibrillation of raw materials SE pre-treatment did not improve their thermal conductivity. The determined bulk density of loose-fill crops varied in range of 23–184 kg m-3 depending on all variables; the SE pre-treatment showed the most significant effect on its reduction. Based on the study results the most suitable crops residues for bio-based thermal insulation purposes are suggested wheat straw and reeds demonstrating the lowest values of bulk density and thermal conductivity.

Optimization of Thermal Conductivity vs. Bulk Density of Steam-Exploded Loose-Fill Annual Lignocellulosics

“…As it is known, very important factors influencing thermal conductivity are raw materials and the density of thermal insulation materials [ 8 , 19 ]. So, based on the above literature review and our previous studies [ 20 , 21 ], this paper continues the research of thermal insulation materials from locally available annual LCB such as wheat straw, water reed and corn stalk providing a deeper insight of the detected properties and optimizing the relationship between thermal conductivity and bulk density. The main purpose of the study was to find out an optimal bulk density of the investigated loose-fill LCB depending on SE conditions for further research providing other important properties like settling, water vapor diffusion, reaction to fire, mold fungi resistance and volatile emission.…”

“…Based on the previous studies [ 20 , 21 ], the chopped raw LCB, first, was moisturized up to 80% of moisture content by immersing it in water. The moisture content (dry basis) of moisturized LCB was detected by a moisture analyzer (Precisa XM 120, Dietikon, Switzerland) following the standard (EN 14774-3) methodology [ 22 ].…”

Mold Fungal Resistance of Loose-Fill Thermal Insulation Materials Based on Processed Wheat Straw, Corn Stalk and Reed

“…The studies reviewed above highlight the importance for further research into mold fungi’s effect on existing and newly developed LCB-based thermal insulation products. Therefore, our study continues the research of new thermal insulation materials [ 27 , 28 ] from locally sourced and annually harvested LCB such as wheat straw, water reed and corn stalk, and provides the results of mold fungi resistance. The research is significant due to the fact that the selected raw materials are widely available around the world and the obtained results could be useful for the development of and increase in LCB-based thermal insulation.…”

“…Based on the previous studies [ 27 , 28 ], the chopped raw LCB was moisturized up to 80% moisture content by immersing it in water for 24 h. After, the LCB was drained and separately treated in a home-made SE device of original construction with a 0.5 L batch reactor at constant conditions: temperature of 230 °C, residence time of 30 s and maintaining a pressure of 30 bar. After, the wet SEP was collected and manually squeezed in a juice-like press to remove the liquid fraction.…”

Mold Fungal Resistance of Loose-Fill Thermal Insulation Materials Based on Processed Wheat Straw, Corn Stalk and Reed

“…The studies reviewed above highlight the importance for further research into mold fungi effect on existing and newly developed LCB-based thermal insulation products. Therefore, our study continues the research of new thermal insulation materials [21,22] from locally sourced and annually harvested LCB such as wheat straw, water reed and corn stalk providing results of mold fungi resistance. The research is significant due to the selected raw materials are wide available around the world and the obtained results could be useful for development and increase of LCB-based thermal insulation market share.…”