Physio-chemical pretreatments for improved methane potential of Miscanthus lutarioriparius

Bio-energy production from lignocelluloses biomass has gained a lot of interest in recent years. Miscanthus sp. are high lignocelluloses biomass yielding with relatively high carbohydrate content cultivable on different soils and under climatic conditions. However, the lignocellulosic nature means that cellulose and hemicellulose are cover by lignin network that might limit hydrolysis. In this study, physical pretreatments (size reduction), physiochemical (steam expulsion) and chemical pre-treatments (mild acid and alkaline) were investigated in a view to improve the anaerobic biodegradability of Miscanthus lutarioriparius for biogas production. Prior to the pretreatment and methane potential test, the compositional analyses of M. lutarioriparius was performed in order unveil the carbohydrate (cellulose and hemicelluloses), protein and lignin contents. From these analyses, the maximum theoretical methane potential was estimated. All pretreatments led to solubilisation of organic matter as was evidenced by increase dissolve COD and ammonium nitrogen. There was a positive correlation between dissolved COD and methane yields meanwhile a negative correlation was observed for reducing sugar and methane yields. The achieved methane yields ranged from 121 to 238 ml CH4/g VS. Steam explosion, 0.3 M NaOH treatment and 0.5 mm size reduction led to the highest increases in methane yields, which was in the order of 57% with regard to the untreated samples. These improvements resulted in 71% of theoretical methane yield of M. lutarioriparius. Alkaline pretreatment in particular also improve the rate of methane production as was evidenced by the fact that as high 15% of the final methane yield that was achieve on the first day as compared to only 3% for the untreated sample. Indeed, the time to reach 90% of the ultimate methane yield was reduced by 13 days following 0.3 M NaOH treatment. M. lutarioriparius may therefore represent an interesting candidate as a lignocellulosic feedstock for biogas production after suitable pretreatment. (C) 2015 Elsevier Ltd. All rights reserved.