Granular Activated Carbon and Organic Loading Interactions in Methane Fermentation: An Inverse Load-Dependent Relationship and Absolute Microbial Abundance Analysis

This study addresses volatile fatty acid (VFA) accumulation, a key issue limiting methane fermentation under high organic loading rate (OLR) conditions. Batch experiments were conducted with GAC (0–10%) under various OLRs (1:0.5–1:10) to investigate its effect on biogas yield, methane purity, and microbial interactions. Higher GAC levels (7.5% and 10%) significantly enhanced biogas production (750–800 mL/g VS) and methane concentration (–70%) while shortening stabilization time. A continuous system with 10% GAC showed suppressed VFA accumulation, stable pH (7.0–8.1), and improved organic matter degradation. This work quantitatively evaluates the link between GAC dosage, DIET induction, and microbial community shifts under high OLR. These findings highlight GAC as an operationally simple and potentially cost-beneficial strategy for stabilizing methane fermentation, particularly in decentralized or small-scale applications.