Monitoring of a Discontinuos Dry Fermentation Plant Based on Mobile Biogas Containers

Dry fermentation combines the possibility of use of biogenous waste and energy utilisation in a technically simple process. In this study a new and innovative product, the Mobigas Container Biogas Plant, was monitored. The aim was to develop an ’indicator system’ to predict, control and regulate the performance of the plant and to provide operators with guidelines how to run the plant stable achieving high energy yields. Technical informations were gained by analyzing process parameters such as temperature, pH-value, redox potential, volatile organic acids and buffer capacity. Due to the discontinuous operation, the process can mainly be controlled by adjusting the starting conditions. Special emphasis was laid upon sufficient inoculation of the substrate. This is achieved by reusing digestate of the previous batch. Pilot operations have shown that after a retention time of three weeks the ratio of reused digestate as inoculum was the most important parameter. To achieve good biogas yields optimal process parameters such as temperature have to be kept constant and within an optimal range. The container plant is now commercially available and the development of a liquid phase fermentation system underway.