Enhancement of biogas production from lignocellulosic materials by NMMO and Organosolv pretreatments

This study investigated the effects of two different chemical pretreatments on the methane yields of three lignocellulosic materials (LMs), namely hazelnut skin and cocoa shells, generated during the industrial processing of the raw agricultural products, and rice straw, which is one of the most abundant agricultural wastes worldwide. Initially, the three LMs were separately pretreated with an organic solvent, called N-Methylmorpholine-N-oxide (NMMO), at 120°C for 3 h. Consequently, batch bio-methane production (BMP) tests were performed under mesophilic (i.e. 37 ± 2°C) conditions for 40 days. In a similar experimental run, the effects of organosolv pretreatment on the three LMs were investigated. 50% ethanol was used as organic solvent and the pretreatment was carried out at 150 and 180°C for 30 min. Both NMMO and organosolv pretreatments were particularly effective for rice straw, enhancing the biodegradability of the LM and, consequently, increasing the biogas yields compared to those of the untreated material.