Chinese‐type biodigester design using an automatic PLC-based control system in the Chillón Valley, Peru.

Abstract

The research proposes improving the design of a Chinese-type biodigester located in the Chillón Valley by implementing an automatic control system based on PLC. The study starts from the current problem: these biodigesters require high human intervention, have little uniformity in the substrate mixture, and have variations in biogas production due to the lack of controlled agitation. Different types of biodigesters are analyzed, and the Chinese type is selected for its robustness and low cost. For the substrate of guinea pig manure mixed with water, properties such as density and viscosity are determined, which justify the need to install a mechanical agitation system. Based on these properties, the necessary motor power is calculated, determining that a 0.75 kW motor with a marine propeller is adequate to maintain a homogeneous mixture. The volume of biogas produced daily (2,495 m3/d) and its energy potential were also estimated, demonstrating that it can generate useful energy for self-consumption. Finally, an automated system was designed with a PLC, level sensors, contactors, gear motors, and electrical protections, allowing for the control of mixing times, levels, and motor operation without constant intervention. The study concludes that automation is technically and operationally viable, improving process efficiency, reducing human error, and increasing stability in biogas generation.