Assessment of the biomethane potential of commingled farm residues with sewage sludge and its techno-economic viability for rural application

Abstract

A significant share of the overall greenhouse gas (GHG) emissions comes from uncontrolled open-burning practices stemming from failed on-farm waste management, and a considerable fraction of the population still lacks a steady sewage network. In the past, anaerobic digestion (AD) of specific crop residues has been studied, and the potential of biomethanation from sewage sludge amendment has been explored. Compared with the aerobic treatment facilities, the cost set up for anaerobic treatment units, even though it is high, initially gives long-term returns. Owing to the questionable success of centralized biomethanation facilities in developing countries and the immense potential of anaerobic digestion to combat non-renewable energy, decentralized AD interventions are the need of the hour. Therefore, this research explores the biomethane potential of untreated commingled farm residues (CFRs) studied across 4 S/I ratios (1, 1.5, 2, 2.5). The results from the biomethane potential tests indicate that the S/I ratio 2.5 operating with sewage sludge as inoculum gives the highest biogas yield. Further, the study explores bio-methanation kinetics using the modified Gompertz model (MGM) and logistic function (LF) and comments on the universality of MGM in describing bio-methanation kinetics in a much more significant way as compared with LF. Finally, the study accounts for efficient financial decision-making for rural communities when planning for a decentralized compressed biogas (CBG) facility. It was also observed from the techno-economic analysis that the estimated biogas from a 100-L scaled-up reactor could satisfy 4-cylinder requirements/month, thereby contributing to the achievement of the sustainable development goals (SDGs). � The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2024.