The kinetics for mathematical modelling on the anaerobic digestion of organic waste - a review

Abstract

Anaerobic digestion is a biological process that could provide high valorisation value of waste by producing biogas as a form of renewable energy and the digesate as biofertiliser. A mathematical model is an essential tool to observe, predict, simulate and optimise the system's behaviour at different conditions. The modelling approach for wet digestion and dry digestion is different due to the presence of solid content. The selection of the limiting step for modelling can be influenced by both substrate and microbial loadings. The complex substrate is heterogenous by nature and consists fractions of organic matter with different biodegradability. The formulation of the model is affected by the type of substrates and its characteristic, which exhibits different substrate degradation kinetics, intermediate production and consumption behaviour and the biogas production. This review aims to look at the rationalisation and findings that lead to the different formulation of the models, from the point of view of the variation of the organic waste, including municipal solid waste, food waste and animal manure. Recent research results for the anaerobic digestion of organic waste is also discussed, which serves to provide better insight for future generalisation of a model.