Enhancing kitchen waste anaerobic digestion by recycled aluminum industry waste: Alkali treatment and potential electron transfer mechanism

Abstract

Kitchen waste has become a significant environmental concern worldwide. Red mud, an industrial solid waste characterized by its porous structure and high iron oxide content, exhibits potential as a conductive conduit in the direct interspecies electron transfer (DIET) pathway. In this study, red mud pretreatment of kitchen waste was conducted to enhance anaerobic digestion (AD). The effect and mechanism of enhancing kitchen waste AD by red mud pretreatment was studied for the first time. Results indicated that red mud pretreatment could accelerate the hydrolysis of organic compounds and alleviate the acid inhibition. Consequently, the methane production rate was increased from 260.7 mL/g VS to 402.3 mL/g VS, i.e., up to 54.3%. And volatile solids removal efficiency was increased from 53.9% to 73.1%, i.e., up to 35.6%. Furthermore, microbial community analysis revealed the enrichment of electrochemically active bacteria (Synergistaceae), acetogenic bacteria (Syntrophomonadaceae) and methanogens (Methanobacterium and Methanosarcina), which played essential roles in interspecies hydrogen transfer (IHT) and DIET. This study showed that red mud pretreatment has the potential to enhance kitchen waste AD which contributes to carbon mitigation. It also threw the potential new insights to the relative mechanism.