Densification of biomass can address handling, transportation, and storage problems and also lend itself to an automated loading and unloading of transport vehicles and storage systems. The purpose of this study is to compare the physicochemical properties of briquettes made from different feedstocks. Feedstocks such as corn stover, switchgrass, prairie cord grass, sawdust, pigeon pea grass, and cotton stalk were densified using a briquetting system. Physical characterization includes particle size distribution, geometrical mean diameter (GMD), densities (bulk and true), porosity, and glass transition temperature. The compositional analysis of control and briquettes was also performed. Statistical analyses confirmed the existence of significant differences in these physical properties and chemical composition of control and briquettes. Correlation analysis confirms the contribution of lignin to bulk density and durability. Among the feedstocks tested, cotton stalk had the highest bulk density of 964 kg/m3 which is an elevenfold increase compared to control cotton stalk. Corn stover and pigeon pea grass had the highest (96.6%) and lowest (61%) durability.

Pretreatment is being the first and most expensive step, it has pervasive impacts on all other steps in overall conversion process. There are several pretreatment methods using physical, chemical, and biological principles which are under various stages of investigation. Extrusion can be used as one of the physical pretreatment methods towards biofuel production. The objective of this study was to evaluate the effect of barrel temperature and screw speed on sugar recovery from corn stover, to select a suitable enzyme combination and its ratio. Corn stover was pretreated in a single screw extruder with five screw speeds (25, 50, 75, 100, and 125 rpm) and five barrel temperatures (25, 50, 75, 100, and 125 degrees C). In order to select a suitable enzyme combination and ratio, different levels of cellulase and beta-glucosidase, multienzyme complex and beta-glucosidase were used during saccharification of pretreated corn stover. From the statistical analysis, it was found that screw speed and temperature had a significant effect on sugar recovery from corn stover. Higher glucose, xylose, and combined sugar recovery of 75, 49, and 61%, respectively, were recorded at 75 rpm and 125 degrees C. This pretreatment condition resulted in 2.0, 1.7, and 2.0 times higher than the control sample using 1:4 cellulase and beta-glucosidase combination.

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Research on biomass pretreatment to enhance enzymatic digestibility has been done for more than decades, but a viable continuous pretreatment method needs to be developed. Extrusion has the potential to be a viable continuous pretreatment method. This study investigated the effect of compression ratio (2:1 and 3:1), screw speed (50, 100, and 150 rpm), and barrel temperature (50, 100, and 150 degrees C) on the sugar recovery from switchgrass (SG) and prairie cord grass (PCG) over a range of moisture contents (15, 25, 35, and 45% wb).The pretreated samples were subjected to enzymatic hydrolysis for sugar recovery measurement. Statistical analyses revealed that a 3:1 screw compression ratio (compared to 2:1) increased glucose recovery by 12% and 8% and combined sugar recovery by 37% and 40% for SG and PCG, respectively. For SG, the highest sugar recovery (45.2%) was obtained at the lowest screw speed (50 rpm) and the highest temperature (150 degrees C) with moisture content of 15%. The highest glucose, xylose, and combined sugar recovery of 61.4%, 84.3%, and 65.8% were recorded for PCG extruded at a screw speed of 50 rpm and a temperature of 50 degrees C with a moisture content of 25%. Glycerol and acetic acid were byproducts found in low concentration (0.02-0.18 g/L) for both biomass.

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