**Evaluation on the Methane Production Potential of Wood Waste Pretreated with NaOH and Co-Digested with Pig Manure**

**Renfei Li 1,2, Wenbing Tan 1,2, Xinyu Zhao 1,2, Qiuling Dang 1,2, Qidao Song 3, Beidou Xi 1,2,\* and Xiaohui Zhang 1,2,\***


Received: 8 June 2019; Accepted: 14 June 2019; Published: 17 June 2019

**Abstract:** Wood waste generated during the tree felling and processing is a rich, green, and renewable lignocellulosic biomass. However, an e ffective method to apply wood waste in anaerobic digestion is lacking. The high carbon to nitrogen (C/N) ratio and rich lignin content of wood waste are the major limiting factors for high biogas production. NaOH pre-treatment for lignocellulosic biomass is a promising approach to weaken the adverse e ffect of complex crystalline cellulosic structure on biogas production in anaerobic digestion, and the synergistic integration of lignocellulosic biomass with low C/N ratio biomass in anaerobic digestion is a logical option to balance the excessive C/N ratio. Here, we assessed the improvement of methane production of wood waste in anaerobic digestion by NaOH pretreatment, co-digestion technique, and their combination. The results showed that the methane yield of the single digestion of wood waste was increased by 38.5% after NaOH pretreatment compared with the untreated wood waste. The methane production of the co-digestion of wood waste and pig manure was higher than that of the single digestion of wood waste and had nonsignificant di fference with the single-digestion of pig manure. The methane yield of the co-digestion of wood waste pretreated with NaOH and pig manure was increased by 75.8% than that of the untreated wood waste. The findings indicated that wood waste as a sustainable biomass source has considerable potential to achieve high biogas production in anaerobic digestion.

**Keywords:** wood waste; biofuel; lignocellulosic biomass; NaOH pretreatment; anaerobic co-digestion
