Soft magnetic ferrite for enhanced anaerobic digestion of food waste: Effects on methane production and magnetic recovery.

Soft magnetic ferrite (SMF) is a potentially efficient anaerobic digestion (AD) additive that can be recovered simultaneously along with the microorganisms it carries. In this study, two typical SMFs (Fe3O4 and γ-Fe2O3) were compared in batch experiments to investigate their effects on food waste AD and to examine the recovery characteristics of both the SMFs and the microorganisms they carried after AD. The results showed that Fe3O4 and γ-Fe2O3 addition increased methane production by 31% and 68% respectively, compared with the control treatment. Both SMF materials and enriched microorganisms were effectively adsorbed post-AD using a magnet. The observed enhancement in biomethanization after SMF addition was likely due to enhanced syntrophic acetate oxidation and hydrogenotrophic methanogenesis, and direct interspecific electron transfer. γ-Fe2O3 outperformed Fe3O4 due to its high recycling rate and ability to promote Methanosarcina growth. This study provides a potential economically efficient solution for developing AD enhancement technologies.