Abstract

A novel reactor was developed in this research to simultaneously produce biogas from solid- and liquid-state anaerobic digestions in one container for the first time. Excess heat from the outer liquid-state anaerobic digestion (OL-AD) of POME was transferred to the inner solid-state anaerobic digestion (IS-AD) of EFB for promoting thermophilic digestions (55 °C and 70 °C). Continuous operations at various hydraulic retention times were performed. Bacteria and archaea communities were identified. The results showed that the maximum methane yields were 507.07 and 125.84 mL-CH4/g-VS for OL-AD and IS-AD, respectively. In OL-AD, raising temperature increased the methane yield by 6.4%. In IS-AD, the yield was not significantly affected by elevated temperature. However, the pretreatment of EFB with NaOH increased the methane yield by 14.1%. The main bacteria and archaea communities in OL-AD and IS-AD were found similar. The novel reactor could save energy, reduce costs and digester space, and increase the methane yield.