Mathematical Modeling of the Hydrolysis Phase in Anaerobic Digestion of Solid Waste

Abstract

Anaerobic digestion has been in use for many decades, and its range of uses keep on expanding although it has a reputation of being unreliable and unpredictable. Anaerobic digestion could provide a sustainable solution to waste disposal as well as power generation, if the process could be controlled as desired. This study was done in order to observe the behavior and to optimize the hydrolysis phase in anaerobic digestion of biodegradable solids, by developing a mathematical model for the process. Considering all aspects, a surface related model was used to describe the process since hydrolysis of complex solid substrates is dominated by surface phenomena. In order to narrow down the scope of the research, initial experimentation was focused on pure carbohydrates only. Boiled rice was selected as the substrate since it is readily available and because it is a pure form of carbohydrate. Through experimental data and the aid of the software Matlab2013, the model parameters were determined to be KS = −1 and rmax = 1.004 mmol/dm3.day under operating conditions of 1 atm pressure and temperature of 28 ℃. Further developments and improvements to this model are essential to be able to predict hydrolysis of complex substrates at any given operating condition. The improved model may someday result in a capable and efficient waste management system which is sustainable, ergonomic and efficient.