Evaluating in-vessel composting in treating sewage sludge and agricultural waste by examining and determining the kinetic reactions of the process

This paper presents the evaluation of the performance of an in-vessel composting system by examining the kinetic reactions of the processes developed for the treatment of sewage sludge and agricultural waste. The aim of this work is (a) to describe the composting process using a kinetic model that is based on the biodegradable organic matter losses during decomposition of the substrate, (b) to evaluate the efficiency of the bioxidation process that takes place in the system and (c) to determine the factors and the rate at which they limit the composting process. The simulation of the composting process considers a first-order kinetic model including the environmental parameters (environmental correction factors) that influence bioxidation of the biodegradable organic matter (BOM) of the substrate namely temperature, moisture content and oxygen concentration. The experimental results, recorded and monitored throughout the composting processes, were fitted using the proposed model. The results obtained suggest that the system operates efficiently by recording increased levels of BOM losses, high decomposition rates while composting limitations, due to the environmental conditions, is not significant during the main stages of the processes.