COMPOSTING OF MUSHROOM SUBSTRATE IN A FERMENTATION TUNNEL - COMPOST PARAMETERS AND A MATHEMATICAL-MODEL

Phase II of composting of mushroom substrate was studied in bulk ferme ntation tunnels. Compost data are given on heat production, settling a nd mass reduction, porosity and thermal conductivity. Mass and moistur e determinations at the end of the process revealed slightly positive gradients in the direction of the air stream. The highest rate of degr adation occurred during the first 2 days. A mathematical model of mass and heat transfers was made for a better understanding of the complex composting process. Differential equations were solved with time-depe ndent analysis using a Continuous Simulation and Modelling Program (CS MP). In the calculations, the substrate was divided into theoretical l ayers of equal thickness but of different density and porosity. The mo del predicts the time-course of the process taking into account the mo isture content and the filling height of the compost, and the amounts of supplied fresh air and recirculated air. The calculated data includ e the oxygen demand, the water and dry matter losses, the temperatures in the various layers, and the loss of conductive heat through the wa lls of the containers in the tunnel. Calculated data corresponded with actual process data. Temperatures were correct within 3 degrees C and weight losses within 5%.