Development and calibration of a model for biohydrogen production from organic waste

Existing models for H₂ production are capable of predicting digester failure caused by a specific disturbance. However, they are based on studies using simple sugars, while it is known that H₂ production and fermentation kinetics vary with the composition and characteristics of the substrate used. Because the behaviour of biological processes may differ significantly when the digesting material is a complex matrix, such as organic waste, the aim of this study was to develop and calibrate a mathematical model for the prediction of hydrogen production on the basis of the results obtained from a laboratory scale experimental study using source-selected organic waste. The calibration was carried out for the most important kinetic parameters in mesophilic anaerobic digestion processes and also served as a sensitivity analysis for the influence of both the specific growth rate (μ_max and the half velocity constant (k_s), both of which are strongly dependant on the substrate used. High values of μ_max led to a shorter lag-time and to an overestimate of the cumulative final H₂ production relative to the experimentally measured production. Additionally, high values of k_s associated with amino acid and sugar fermentation corresponded to a lower rate of substrate consumption and to a greater lag-time for growth of hydrogen-producing microorganisms. In this case, a lower final H₂ production was predicted than that which was experimentally observed. Because the model development and calibration provided useful information concerning the role of the kinetic constants in the analysis of a fermentative H₂ production process from organic wastes, they may also represent a good foundation for the analysis of fermentative H₂ production from organic waste for pilot and full-scale applications.