1d-space Dynamic Mathematical Model of the Composting Process

INTRODUCTION Mathematical modelling is a helpful tool to analyse complex systems, but its development and application to the composting process has been rather scarce up to date. The use of mathematical models is common in complex biological processes such as the activated sludge wastewater treatment and the anaerobic digestion process, both systems operating on a single isothermal phase. Composting occurs in a porous media where the three phases, solid, liquid and gaseous, are present and interact between them in a non-isothermal state. A global methodology for the presentation of the biological and physical phenomena involved is not yet fully developed. A first step in that direction was the model of a completely mixed composting reactor (Solé-Mauri et al., 2007). When trying to expand the model to space all state variables become space-distributed and all physical transport phenomena originated by mass and temperature gradients as well as bulk gas flow in the porous media and mass settlement must be considered. Although there are some published models of the composting process, few consider the mass and energy transport phenomena in detail, not allowing an explanation of many of the observed characteristics of the composting process operation. The present work presents the developed methodology to build up a deterministic mathematical model of the composting process, based on the basic laws of physical and biological elementary processes, with the objectives to simulate and to explain the behaviour of one-dimension (1D) column composting reactor, and to have a framework for further mathematical modelling developments.