The influence of biodegradability and inoculum-to-substrate ratio on the anaerobic digestion performance and microbial diversity

<p><span lang="EN-US" style="line-height:32px;color:black;font-size:12pt">Continuous-flow anaerobic digestion (AD) of wheat straw 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 <em>Methanomicrobiaceae</em> to <em>Methanosarcinaceae</em> dominance upon biochar addition, correlating with <em>mcr</em>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&#39;s potential to stabilize performance and enrich functional microbial communities under stress conditions.</span><br /></p>