Biogas production from anaerobic mono- and co-digestion of lignocellulosic feedstock: Process optimization and its implementation at community level

Abstract

Anaerobic digestion of lignocellulosic biomass has gained attention in recent years due to its increase availability and productivity. In this study, anaerobic mono- and co-digestion of three lignocellulosic biomass, viz. duckweed, switchgrass, and rice straw, were performed in 1 litre laboratory-scale batch reactors. The initial biochemical methane potential (BMP) test was performed at three different total solids concentrations (10%, 15%, 20%) and cattle dung: feedstock ratios (1:1, 1:1.5, 1:2) under mesophilic conditions (28–32 °C) for 36 days. Co-digestion of feedstocks at 1:1 ratio yielded better results than other cattle dung: feedstock ratios. Optimized physical parameters were further implemented for a scale-up co-digestion study of biogas potential from 4 m 3 community-size biogas digesters. The investigation was performed for 60 days maintaining a hydraulic retention time (HRT) of 40 days, and a comparative analysis with mono digestion of cattle dung was also analyzed. Average daily biogas production for digester containing rice straw and cattle dung was 0.36 m 3 /kg-VS, whereas it was 0.34 m 3 /kg-VS and 0.32 m 3 /kg-VS for switchgrass and duckweed, respectively. An overall comparative analysis of the biogas production and its composition for both BMP tests and continuous processes are discussed in this work. • Anaerobic digestion of duckweed, switchgrass and rice straw in batch reactors. • Investigation of biogas potential in community-level at the optimized parameters. • Biogas production was higher at 10% and 15% TS concentration for mono digestion. • Co-digestion with cow dung at 1:1 CD: FS ratio yielded higher biogas production. • Higher biogas production was found in co-digestion of rice straw and cow dung.