A Comparative Study of the Effects of Extrusion on Lignocellulose Structure and Biogas Production from Wheat Straw and Digested Wheat Straw

Extrusion, a physical pretreatment, is normally used for the pretreatment of lignocellulosic materials to improve biogas production. Wheat straw (WS) and its solid digestate (digested wheat straw, WSD) were selected to evaluate the effect of extrusion on lignocellulose structure and biogas production from WS and WSD. The WS and WSD were extruded and then were used for biogas production at (37 +/- 1) ? in a batch model. The results showed that the cellulose, hemicellulose, and lignin contents of WS and WSD were 28%, 25%, and 14% and 30%, 25%, and 22%, respectively, while the cumulative biogas yields of WS and WSD were 179 and 57 mL/g TSadded (total solid, TS). After extrusion treatment, the cumulative biogas yields of WS and WSD were increased by 23% and 152%, respectively, while the cumulative methane yields of WS and WSD were increased by 27% and 192%, respectively, compared to the unextruded biomass. The results of scanning electron microscope and specific surface area (SSA) indicated that the lignocellulose structure in WSD suffered greater destruction and the increase in the SSA in WSD was 51-percentage points compared to WS pretreated by extrusion. Therefore, it is technically feasible to use extrusion treatment as a pretreatment for the reuse of digested wheat straw for biogas production.