Modeling of Anaerobic Digestion of Organic Fraction of MSW at industrial scale

The industrial process complexity of biogas production is often a drawback to optimization. Kinetic models allowed the understanding of current phenomenon in reactors making possible the automation and control. To deepen the knowledge of the process, a bibliographic research of the scientific, technological and monitoring state-of-art of the anaerobic digestion process was made, including performance calculations to find parameters best suited for optimization. A mathematical model that describes the general degradation of organic fraction of municipal solid waste (OFMSW) in full scale reactors was then developed. The current study is based on models developed by several authors, where it was included the microbial growth kinetics, each one with their own parameters, found in the bibliography. The kinetic flux was divided into three processes: hydrolysis, acidogenic/acetogenic and methanogenic. The model simulates the decomposition of low biodegradable matter in high biodegradable matter, acid formation and production of biogas. It also includes pH calculation and physic-chemical equilibrium relationships among ionized/unionized species. As main simplification, it was considered a biphasic, liquid/gas reactor, isothermal at 35oC with mass transfer between phases, homogenized and stirred perfectly with 5% of total solids and 50% of volatile solids by total solids. The full scale model was applied to Valorlis reactors, optimizing it by objectives, by changing the operational parameters. The model simulates a start-up with the kinetics according to the researched literature. The steady state is achieved after 6 months at which time the variable values are in accordance with the experimental values observed.