A Simple Fuzzy Logic Management support System for Farm Biogas Plants

This article presents a fuzzy logic management support system that facilitates management of farm-based biogas plants. The considered input variables (feeding rate, organic loading rate, anaerobic biogasification potential, biogas production, and the percentage of methane in the biogas) are simple and typically available for full-scale plants. Outputs from the model specify the feeding adjustments required to maintain or restore biological stability and productivity. The support system was applied to a farm-scale case study and also was successfully tested under real operating conditions during a period of nine months on a 330 kW electric power generating biogas plant fed with crop silages. The model correctly identified management changes that improved operation of the plant, preceding decisions made by the plant operator by three or more weeks and providing the correct and proportionate guidance for modifying the feeding regime to restore or maintain optimal digester conditions. These results demonstrate the utility and viability of using the support system to manage farm biogas plants, while improving the associated environmental and economic benefits. The support system can be applied to any biogas plant in terms of its general architecture (input variables, output, and rules), but it requires the calibration of membership functions that are specific to each plant.