Biochemical methane potential from lignocellulosic wastes hydrothermally pretreated

During the second-generation ethanol production, wastes from the hydrothermal pretreatment process are generated. Such rich organic matter residues should be treated. An alternative for that waste is methane production via the anaerobic digestion process. The characterization and the evaluation of the biochemical methane potential (BMP) and hydrolysis rates from the wasted hydrothermally pretreated wheat straw, corn straw, sugarcane, and agave bagasse was investigated. The liquid extracted lixiviates, and the solid fraction of each waste was evaluated. Diauxic methane production was observed for sugarcane and corn liquid fractions and for all the solids fractions. BMP varied from 369 mL CH4/g COD (sugarcane bagasse) to 178 mL CH4/g COD (agave bagasse). The biodegradability percentage was decreasing from sugarcane bagasse (100%), corn straw (65%), wheat straw (55%) and agave bagasse (51%). The liquid fraction produced higher BMP values than the BMP obtained for the solid fraction. The relatively low biodegradability of the hydrothermally pretreated wastes, considering the carbohydrate-rich nature of the substrate, was associated with an inhibitory effect. A double effect caused by the presence of furfural was observed. At lower concentrations, there was an inhibitory effect, while for the high concentration a stimulatory effect was detected.