Optimization of Fertilizer Application Schedule: Utilization of Digestate after Anaerobic Digestion as Liquid Fertilizer

Anaerobic digestion, which is a series of processes to break down organic matter without oxygen is used for waste treatment. Organic wastes with high moisture content, such as livestock excreta, food waste, kitchen garbage, and so on are broken down by microorganisms, and biogas can be obtained. Digestate, which is produced as a byproduct, has rich nutrient and can be used as fertilizer. However, it must be applied in large quantities because the concentrations of nutrient in it are much lower than chemical fertilizer. The objective of this study is to develop a method, which determines the optimum fertilizer application schedule in order to establish minimum digestate utilization system, which consists of slurry spreaders, vacuum trucks for transportation, and reservoirs. In order to achieve this objective, the working hours in each farm field was calculated through the simulation, and the necessary number of vacuum trucks could be obtained in order not to occur idle time.