Anaerobic digestion of food waste with a selective mixed-microbial consortium and its evaluation with different optimization methods

Abstract

Food waste (FW) is a valuable resource for anaerobic digestion (AD) due to its biochemical composition. This study aimed to optimize AD using two widely used optimization methods: Response Surface Methodology with Box–Behnken Design (RSM-BBD) and Taguchi orthogonal array L9. Organic load, oxidation–reduction potential, pH, and hydraulic retention time were evaluated for biogas production and volatile solids removal (VS_r). The Taguchi method assessed responses based on the signal-to-noise ratio, resulting in optimal conditions for AD. After numerical optimization, the predicted biogas production was 440 mL, and VS_r was 19.5%. However, the experimental observations of biogas production were 850  mL, and VS_r was 41%. The RSM-BBD method, calculated based on analysis of variance, resulted in optimal conditions for AD, and after numerical optimization, the predicted biogas production was 852 mL, and VS_r was 43%. However, the experimental observations of biogas production were 906  mL, and VS_r was 44. Despite these results, the study found that Taguchi’s design provided approximate optimization response values and did not allow parameter interaction. In contrast, RSM-BBD provided precise optimal values and details on the impact of individual and combined parameters, making RSM-BBD the preferred choice for optimizing AD systems for better prediction accuracy and reproducibility.