1 Modeling of Anaerobic Digestion of Organic Fraction of MSW at industrial scale Celso C. GONÇALVES(1) 1 ; Filipe G. FREIRE 2 ; Catarina RODRIGUES 3 ; Inês MOURA 3 ; Tiago FARIA 4 ; Susete MARTINS-DIAS 2 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. Key-words: Anaerobic Digestion, Scale-up, Modeling, Monitoring 1 Student MEAMB, IBB- Institute for Biotechnology and Bioengineering, Centre for Biological and Chemical Engineering, Instituto Superior Técnico, Av. Rovisco Pais, 1049-001 Lisboa, Portugal. (Email: celso.goncalves@ist.utl.pt; Tel.+351927660653) 2 Profs, IBB- Institute for Biotechnology and Bioengineering, Centre for Biological and Chemical Engineering, Instituto Superior Técnico, Av. Rovisco Pais, 1049-001 Lisboa, Portugal. (Email: qgfreire@ist.utl.pt ; susetedias@ist.utl.pt; Tel. +351218419065; Fax +351218419062) 3 Engª, EFACEC Ambiente S.A., Divisão de Resíduos Sólidos (Email: cp.rodrigues@efacec.com; inês.moura@efacec.com; Tel. +351214163776; Fax +351214163650) 4 Dr,EFACEC Ambiente S.A., Director da Divisão de Resíduos Sólidos (Email: cp.rodrigues@efacec.com tiago.faria@efacec.com;Tel. +351214163776; Fax +351214163650) 1 INTRODUCTION The industrial process of anaerobic degradation consists on sequential decomposition of organic matter into biogas, which is a mixture of gases composed essentially by 65-70% of CH 4 , 30-35% of CO 2 , H 2 O and H 2 S, N 2 and H 2, (Appels et al., 2008) produced by microbial biomass in oxygen deficient environments. Nowadays, the industrial process is compatible in renewable energy market. Biogas production in Europe achieved 16.7 toe/1000 inhab in 2009. Germany is the biggest producer, with 51.5 toe/1000 inhab of primer energy, obtained from agriculture residues, like crops, and OFMSW. In 2010, Portugal did not go over 2.2 toe/1000 inhab, but had a growth rate production (EUROBSERV’ER, 2010).