Characterization and methane production of different nut residue wastes in anaerobic digestion

Nut residues are common wastes which abandoned with more than 5 million tons in China annually. In this study, anaerobic digestion (AD) was firstly applied to treat 18 kinds of nut residues and their characterization, methane production, and kinetics were comprehensively investigated. Results implied that nut residues with low lignin content, high lipid and carbohydrate contents, such as lotus seed shells (expressed the highest biodegradability of 95.11% among others), showed good performance in AD. Kinetic analysis proved that modified Gompertz and Cone model were well fitted to describe the AD process of nut residues. Multiple linear regression equation was developed to determine the correlation between experimental methane yield and biochemical compositions of different nut residues, based on which, the highest cumulative methane yield could be predicted. The findings of this research provided useful knowledge for bioconversion of nut waste to renewable energy, and also showed a promising possibility for practical industrial application in future. (C) 2017 Elsevier Ltd. All rights reserved.