An integrated energy recovery system for productive biogas applications: Continuous mode operation and assessment

Abstract

The application of biogas as a renewable energy source continues to face competition from conventional energy sources, which are readily available and seemingly cheap. In addition, productive biogas system deployments in Uganda are currently facing challenges related to sustainability of biogas production, which has led to massive dis-adoption in recent years. These systems have failed to utilize alternatives during scarcity of primary feedstock due to lack technical data for energy recovery, which could be linked to insufficient R&D in the biogas sector. Relatedly, global scientific research has placed focus mostly on methane yield improvements through optimization of anaerobic digestion kinetics on lab-scale, with little focus on the enabling environment for these kinetics to thrive in continuously operated systems.This study therefore aimed to develop an integrated energy recovery system that enables alteration of feedstock and control of digester operating parameters for sustainable biogas production in continuously fed digesters. An array of system components was developed and integrated into a state-of-art energy recovery system, which was prototyped and deployed in real working environment for pilot studies. The system was configured to measure the moisture content of the feedstock and then determine and display to the operator the amount of water to be added to optimize the quality of the substrate. The system also monitors the digester operating parameters and prompts corrective action to prevent possible inhibition of biogas production process. Results show that the system is about 33% more efficient than the conventional one, allows alteration of feedstocks, and can be deployed to replace conventional energy usage for productive applications. For instance, a poultry farm with 10,000 commercial layers may have its energy needs be met 100% by the proposed system with a pay-back period of 4.5 years for deep liter system and 3.7 years for battery cage system.