Thermal properties of lignocellulosic biomass barley straw

Abstract

Abstract. Lignocellulosic biomass barley straw is a complex formation of cellulose, hemicellulose, and lignin. The lignin acts as an external crosslink binding hemicellulose and cellulose with cellulose positioned at the inner core of the structure. The lignocellulosic nature makes it naturally resistant to enzymatic and microbial degradation during hydrolysis and fermentation processes. This necessitates pretreatment of lignocellulosic biomass prior to hydrolysis and fermentation. Pretreatment of lignocellulosic biomass involves the application of heat and the response to heat transfer is dependent on thermal properties of the biomass. Therefore, the essential thermal properties of lignocellulosic biomass required for optimization processes were determined. The thermal conductivity was measured using the line heat source method at three levels of temperatures (4oC, 25oC, and 90oC), and calculated using the maximum slope method. The specific heat capacity was investigated using the differential scanning calorimetry (DSC) at three levels of temperatures (70oC, 80oC, and 90oC). Both measurements was done with five levels of ratio of biomass:NaOH solution (1:4, 1:5, 1:6, 1:7, & 1:8) and three levels of hammer mill screen size (0.354, 0.8, & 1.6 mm). Thermal diffusivity was calculated using thermal conductivity, specific heat, and bulk density values. The results obtained shows that temperature plays a significant role in the thermal conductivity of biological materials. Specific heat has linear relationship with temperature at higher ratio of biomass:NaOH solution. Thermal diffusivity did not show any specific trend with the variables studied.