The Influence of Biodegradability and Inoculum‐to‐Substrate Ratio on the Anaerobic Digestion Performance and Microbial Diversity

ABSTRACT Continuous‐flow anaerobic digestion (AD) of wheat straw (WS) is often limited by volatile fatty acid (VFA) accumulation at low inoculum‐to‐substrate ratios (ISRs). Here, biochar (8.0 g/L) recovered methane production in overloaded systems (ISR 0.5, HRT 12 days), increasing yields by 658.45 mL/g‐VS. Microbial analysis revealed a shift from Methanomicrobiaceae to Methanosarcinaceae dominance upon biochar addition, correlating with mcr A gene upregulation. This strategy enhances the AD of refractory feedstocks without diluting the organic load. The results offer insights into optimizing biogas systems treating low‐biodegradability feedstocks at low ISRs, highlighting biochar's potential to stabilize performance and enrich functional microbial communities under stress conditions.