Composting of mushroom substrate in a fermentation tunnel: compost parameters and a mathematical model

Abstract

Phase II of composting of mushroom substrate was studied in bulk fermentation tunnels. Compost data are given on heat production, settling and mass reduction, porosity and thermal conductivity. Mass and moisture determinations at the end of the process indicated slightly positive gradients in the direction of the air stream. The highest rate of degradation occurred during the first 2 days. A mathematical model of mass and heat transfers was devised. Differential equations were solved with time-dependent analysis using a Continuous Simulation and Modelling Program (CSMP). In the calculations, the substrate was divided into theoretical layers of equal thickness but of different density and porosity. The model predicts the time-course of the process taking into account the moisture content and the filling height of the compost, and the amounts of supplied fresh air and recirculated air. The calculated data include the oxygen demand, the water and dry matter losses, the temperatures in the various layers, and the loss of conductive heat through the walls of the containers in the tunnel. Calculated data corresponded with actual process data. Temp. were correct within 3 degrees C and weight losses within 5%.