Anaerobic co-digestion of Cannabis ruderalis straw and blackwater: hydrothermal pretreatment assessment and mono/co-digestion analysis

Abstract The recalcitrant structure of Cannabis ruderalis straw (CRS) inhibits the recovery of bioenergy from its anaerobic digestion. This paper attempted to estimate the digestive performance of CRS mono-digestion and its co-digestion with blackwater (BW) by hydrothermal pretreatment at different temperature (120, 140 and 160 °C). The solubilization of CRS increased as the treatment temperature increased. The methane yield from CRS-BW co-digestion was 1.2–1.6-fold of that from CRS mono-digestion. The maximum methane yield of 278.66 mL/g VS from CRS mono-digestion was obtained at 160 °C, while from CRS-BW co-digestion, it was obtained at 120 °C (351.35 mL/g VS), indicating that BW weakened the inhibitory effects of substances produced in the hydrothermal pretreatment of CRS on subsequent digestion. Path analyses suggested that the maximum determination coefficient of the methane yield was soluble chemical oxygen demand (SCOD) for CRS mono-digestion and volatile fatty acids (VFAs) for CRS-BW co-digestion.