Effects of digestate recirculation on a two-stage anaerobic digestion system, particularly focusing on metabolite correlation analysis

• Published in: Bioresource technology Vol. 251; pp. 40 - 48
• Main Authors: Wu, Chuanfu, Huang, Qiqi, Yu, Miao, Ren, Yuanyuan, Wang, Qunhui, Sakai, Kenji
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.03.2018
• Subjects: Anaerobic digestion; Digestate recirculation; Food waste; Metabolite correlation analysis; Two-stage digestion; Food waste; Two-stage digestion; Metabolite correlation analysis; Anaerobic digestion; Digestate recirculation
• ISSN: 0960-8524; 1873-2976
• DOI: 10.1016/j.biortech.2017.12.020

•Effect of digestate recirculation on a two-stage anaerobic digestion was evaluated.•Digestate recirculation positively affected the methane yield.•With digestate recirculation, the maximum methane yield was 503.0 mL/g-VS.•Hydrolysis degree of greater than 75% was crucial to fully recover methane from FW.•Ammonium accumulation should be prevented in the above mentioned systems. Single-stage (S-N treatment) and two-stage anaerobic digestion with (T-R treatment) and without digestate recirculation (T-N treatment) for methane production using food waste (FW) were comparatively evaluated to examine the effects of digestate recirculation on anaerobic digestion (AD). Digestate recirculation positively affected the methane yield and organic loading rate (OLR). Metabolite correlation analysis revealed that a systematic hydrolysis degree of greater than 75% is crucial to achieve the complete recoverable yield of methane from FW. Digestate recirculation also markedly increased the system alkalinity, maintaining an optimum pH for methanogens. However, the ammonium accumulated by T-R treatment would destroy the metabolic balance between the hydrolytic bacteria and methanogens, especially at a critical OLR. Therefore, the appropriate control of two-stage AD systems with digestate recirculation is limited not only to OLR regulation but also to the prevention of ammonium accumulation.