Anaerobic digestion of food waste: Correlation of kinetic parameters with operational conditions and process performance

The correlations between kinetic parameters and both operational conditions and process performance during the anaerobic digestion of food waste were investigated. Substrate concentration (SC), biomass concentration (BC), and substrate-inoculum ratio (S/I) were selected as the operational conditions, while first-order and modified Gompertz models were introduced to evaluate digestion kinetics. The results indicated that no significant correlations between both hydrolysis and methanogenesis kinetic parameters (k and Rm) relative to the operational conditions and process parameters could be determined; however, k/Rm′ was observed to significantly correlate with these parameters. Specifically, substrate load (both SC and S/I) positively influenced k/Rm′ via its impact on volatile fatty acid (VFA) and pH, while BC reduced k/Rm′ by increasing the alkalinity of the system. Moreover, k/Rm′ was negatively correlated with process efficiency. The methane recovery rate exceeded 90% when 1.55 < k/Rm′ < 3.13, but decreased by 50% when k/Rm′ > 4.64 (p = 0.05). These findings provide a scientific foundation for predicting the behavior of anaerobic systems and optimizing the digestion process.