Two-Stage Dry Anaerobic Digestion Process Control of Biowaste for Hydrolysis and Biogas Optimization

An advanced management system is offered which adapts to most of the two-stage anaerobic dry treatment plants that do not benefit from a local expert in biowaste treatment. This approach takes advantage of pH sensors to control the process within the optimal range to enhance the hydrolysis and to stabilize and increase the biogas production. By applying automatic pH control in the operational regime by a shift between direct recirculation in the first stage or using digestate of the second stage for percolation, the pH in the first stage could be kept low at pH 5.2 ± 0.2 over the whole operation period. The results demonstrate that the energy efficiency of the two-stage dry anaerobic digestion process can be significantly increased by controlling the pH in the first stage.