Intervention Strategies for the “Inhibited Steady State” Dry Thermophilic Anaerobic Digesters: The Mitigation Mechanisms of Tailored Biochar

Abstract

Compared with the single inhibitory condition, the "inhibited steady state" caused by the coaccumulation of volatile fatty acids and ammonia is more common in actual biogas projects. However, the application of tailored biochar to full-scale anaerobic digester samples under the "inhibited steady state" still remains elusive. The present study evaluated the effectiveness of regularly prepared biochar (2 cm biochar) and tailored biochar (<5 μm biochar and high-electron-donating-capacity (high-EDC) biochar) in alleviating the "inhibited steady state" with double stress from high concentrations of ammonia and propionic acid. It showed that tailored biochar reduced the lag phase (31.7−41.9%) and increased the cumulative CH 4 production (5.6−37.1%) compared with the traditional intervention strategy of high-ratio inoculation. Moreover, high-EDC biochar significantly promoted the utilization and conversion of propionic acid by the colonization of Syntrophobacter, Smithella, and its methanogenic partners (Methanobacterium and Methanosaeta). Comparative analysis of the microbial diversity and the amount in the adaptive, steady, and later stages showed that hydrogenotrophic Methanobacterium and Methanosarcina were actively resistant to the "inhibited steady state". In addition, tailored biochar promoted the enrichment of biochar-biofilm consortia. The outcome provides a crucial reference for exploring tailored biochar to be a promising antidote for rescuing a seriously failed digester in actual biogas plants.

Understanding Anaerobic Co-digestion of Organic Wastes through Meta-Analysis

“…Furthermore, under alkaline and thermophilic conditions, methanogenesis is primarily governed by hydrogenotrophic methanogenesis (HM), − which is more thermodynamically favorable for methane production than acetoclastic methanogenesis (ACM) (see standard Gibbs free energy changes, Table S3). This metabolic shift is reflected in the changing abundance of methanogens, from Methanosaeta , typically involved in ACM, and Methanolinea , involved in HM, to Methanosarcina , which participates in both pathways, and Methanoculleus , which is associated with HM. ,− This transition is accompanied by an increased abundance of F420 (8-hydroxy-5-deazaflavin), a vital hydride carrier in HM. , …”