Rising industrial waste generation has intensified the demand for sustainable energy solutions, with anaerobic co-digestion offering a promising approach for waste management and renewable energy production. This study examines the anaerobic co-digestion of organic food waste (OFW) and waste-activated sludge (WWS) under mesophilic conditions (37 °C) to optimize substrate ratios and enhance biogas production compared to mono-digestion. The highest yield was achieved at a 90:10 OFW:WWS ratio, producing 884 ± 51 NmLBG g−1 VS with 65 % biomethane content, a 7.3 % improvement over OFW mono-digestion. Experiments showed immediate biogas production with no lag phase across all OFW percentages (0 %–100 %). Four kinetic models: First-Order (FO), Gompertz, Modified Gompertz (MG), and Logistic Function (LF), were assessed using statistical metrics (R2, NRMSE, paired t-tests) and time range analysis. The Gompertz model exhibited the best statistical fit (R2: 0.9231–0.9963) and predicted a maximum yield (Gmax) of 874.12 NmLBG g−1 VS at 90:10, but its non-zero lag phase conflicted with observations. The MG model, with a zero-lag phase, was selected as most suitable due to its biological relevance and reasonable fit (R2: 0.9231–0.9904). Model predictions (e.g., 851 NmLBG g−1 VS by MG) were within experimental uncertainty, but their bias toward lower values suggests a need for advanced models to enhance late-stage accuracy.
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