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.