ENERGY AND MASS BALANCES IN COMPOSTING PROCESS. MODELLING, SIMULATION AND EXPERIMENTAL VERIFICATION INCLUDING THE EFFECTS OF TURNING FREQUENCY.

C.A: MARTÍN; LOVATO MARÍA; PRONO, ALEJANDRA R.

S. Margherita di Pau, Cagliari

Simposio; XV International Waste Management Symposium; 2015

International Waste Management Association

The composting process is recognized as one of the components of waste management, which more or less is worldwide applied as an alternative for the treatment of biodegradable waste fraction. Moreover, its use for degrading various co-substrates from industry and wastewater treatment plant is constantly increasing. The methodologies used range from systems with modern technology and high operating costs, to others with high manual participation (e.g. in small towns or in developing countries such as Argentina). Compost facilities could be considered as a chemical reactor design. In this sense, mathematical models of the composting process have been based on the solution of heat and mass balances in time, and in a limited number of cases, spatially. Despite the fact that numerous models for the composting process have been published and reviewed, a standard generally accepted model has still not been proposed. This could partly be explained by the fact that composting is characterized by a high degree of intricacy related to the interactions of several biochemical and physical factors in a heterogeneous matrix of gas, liquid and solid phases, which fluctuate considerably over time. Moreover, most of them refer to static piles with forced or natural ventilation aeration and controlled conditions, and there are a very few integrated models published which consider turning windrows and include experimental validation (see for example 1-5)The ability of models to predict process temperatures within a specified margin through to the end of the thermophilic phase and to closely simulate the magnitude and timing of temperature peaks becomes important if models are used to indicate process performance. However, the modelling requires the simultaneous solution of mass and thermal balances including the proposal of kinetics expressions to link the entire equations. This paper addressed to develop a model that include kinetics expressions for organic matter, water and oxygen, as well as mass and thermal energy transfer equations as a function of time, position and geometry. The set of equations are solved simultaneously because they are coupled by means of heat generation by chemical reaction. Runge-Kutta and finite differences numerical methods were applied. Additionally, the averaged temperature was obtained by integration inside the reactor for each time.