A Smart Automation System for the Management and Control of a Medium Scale Digester Plant

The paper describes the implementation of the control logic for the management of a medium-scale digester plant through a smart automation system. Such a digester was developed to produce biogas and biomethane subsequently to anaerobic digestion of agri-food wastes, with a particular interest in olive mill by-products. Temperature and pH are the main parameters that control prototype running and automatism. The plant is fed with two matrices having respectively acid (in the case of olive mill wastewater) and alkaline pH (i.e. livestock manure), thanks to which, substrate pH value is set. The temperature control is ensured by a couple of armoured heater elements, while cooling can occur thanks to a water main directly connected to the digestor. The control logic is implemented for maintaining the temperature and pH values within a certain range to guarantee the optimal process parameters. The smart automation system consists of three PLC units, which manage the sensors to acquire temperature and pH data for process control, and pressure and flow sensors to determine biogas production. A remote control interface was designed to allow manual or automatic control of the plant. The interface enables to navi-gate between four different windows: manual control, automatic control, parameter setting and trends, which shows the real-time measurements provided by the sensors. Furthermore, the interface allows for setting process parameters, controlling process progress and saving data history. Keywords Automation system ·