Comparison of solid-state to liquid anaerobic digestion of lignocellulosic feedstocks for biogas production

► Solid state anaerobic digestion (SS-AD) of eight types of lignocellulosic biomass. ► Liquid anaerobic digestion (L-AD) of eight biomass feedstocks was compared with SS-AD. ► No significant difference in methane yield between SS-AD and L-AD. ► Volumetric biogas productivity of SS-AD was 2- to 7-fold greater than that with L-AD. ► Methane yields from crop residues were higher than those from woody biomass. Lignocellulosic biomass feedstocks (switchgrass, corn stover, wheat straw, yard waste, leaves, waste paper, maple, and pine) were evaluated for methane production under liquid anaerobic digestion (L-AD) and solid-state anaerobic digestion (SS-AD). No significant difference in methane yield between L-AD and SS-AD, except for waste paper and pine, were found. However, the volumetric productivity was 2- to 7-fold greater in the SS-AD system compared with the L-AD system, except for paper. Methane yields from corn stover, wheat straw, and switchgrass were 2–5 times higher than those from yard waste, maple, and pine biomass. Waste paper had a methane yield of only 15L/kg VS caused by souring during SS-AD due to organic overloading. Pine also had very low biogas yield of 17L/kg VS, indicating the need for pretreatment prior to SS-AD. The findings of this study can guide future studies to improve the efficiency and stability of SS-AD of lignocellulosic biomass.