Importance of “weak-base” poplar wastes to process performance and methane yield in solid-state anaerobic digestion

Failure of methane yield is common for anaerobic digestion (AD) of “weak-acid/acid” wastes alone. In order to verify the importance of pH of materials on the process performance and the methane yield, the “weak-base” wastes-poplar wastes (PW) were used as substrate of solid-state AD (SS-AD). The results show that PW could be used for efficient methane yield after NaOH treatment, the total methane yield was 81.1 L/kg volatile solids (VS). PW also could be used for anaerobic co-digestion with high-pH cattle slurry (CM). For the group with NaOH pretreatment, time used for reaching stable state was 2 days earlier than that of the group without NaOH pretreatment. The maximal methane yield of 98.2 L/kg VS was obtained on conditions of 1:1 of PW-to-CM (P/C) ratio and NaOH pretreatment, which was 21.1% (p < 0.05) higher than that of PW. The maximal reductions of total solids (TS), VS, cellulose and hemicellulose were 51.3%, 57.5%, 46.0% and 47.0%, respectively, which were associated with the maximal methane yield. The results indicate that PW could be alone used for efficient SS-AD for methane yield after NaOH treatment.