Enhancing anaerobic digestion of food waste with granular activated carbon immobilized with riboflavin

• Published in: The Science of the total environment Vol. 851; p. 158172
• Main Authors: Huang, Yinhui, Cai, Boquan, Dong, He, Li, Haoyong, Yuan, Jie, Xu, Haiyu, Wu, Hongbin, Xu, Ziyao, Sun, Dezhi, Dang, Yan, Holmes, Dawn E.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 10-12-2022
• Subjects: Anaerobic digestion; Direct interspecies electron transfer; Food waste; GAC; Methanogenesis; Riboflavin; Food waste; Riboflavin; GAC; Anaerobic digestion; Direct interspecies electron transfer; Methanogenesis
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2022.158172

Previous studies have shown that anaerobic digestion of food waste can be enhanced by addition of conductive materials that stimulate direct interspecies electron transfer (DIET) between bacteria and methanogens. However, at extremely high organic loading rates (OLRs), volatile fatty acids (VFAs) still tend to accumulate even in the presence of conductive materials because of an imbalance between the formation of fermentation products and the rate of methanogenesis. In this study, granular activated carbon (GAC) immobilized with riboflavin (GAC-riboflavin) was added to an anaerobic digester treating food waste. The GAC-riboflavin reactor operated stably at OLRs as high as 11.5 kgCOD/ (m3·d) and kept VFA concentrations below 69.4 mM, COD removal efficiencies, methane production rates, and biogas methane concentrations were much higher in the GAC-riboflavin reactor than the GAC- and non-amended reactors. Transcripts associated with genes that code for proteins involved in DIET based metabolism were somewhat more highly expressed by Methanothrix in the GAC-riboflavin reactor. However, it is unlikely that riboflavin acted as an electron shuttle to stimulate DIET. Rather, it seemed to provide nutrients that enhanced the growth of microorganisms involved in the anaerobic digestion process, including those that are capable of DIET.
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•The GAC-riboflavin reactor operated stably at an OLR of 11.5 kgCOD/(m3·d).•The GAC-riboflavin reactor had higher COD removal rates and methane yields.•VFA accumulation stayed below 69.4 mM in the GAC-riboflavin reactor.•Methanobacterium and Methanothrix species dominated the GAC-riboflavin reactor.•Electroactive and syntrophic bacteria were enriched in the GAC-riboflavin reactor.