Valorization of Distillery Spent Wash: Enhancement of Biomethane Potential Through Optimization of Inoculums and Substrates

Abstract

Utilization of distillery spent wash (DSW) as an energy source not only addresses the major environmental concern but also promotes sustainable energy practices. This study evaluates the biomethane potential of DSW through anaerobic digestion. Proximate analysis and optimization of the inoculum-to-substrate (I/S) ratio were performed to enhance biomethane production. Various combinations of substrates, including DSW, rice straw, dry leaves, and kitchen waste, were codigested with inoculums such as cow dung, baker’s yeast, and Saccharomyces cerevisiae strain 2044. Experiments were performed at a controlled temperature of 37°C with an optimal I/S ratio of 2:1 decided based on volatile solid (VS) content. Results indicate that the combination of cow dung and baker’s yeast yielded the highest biogas volume (310.97 NmL), followed by baker’s yeast alone (299.17 NmL) and cow dung alone (261 NmL). The optimal substrate mixture of DSW, cow dung, and kitchen waste exhibited a favorable carbon-to-nitrogen (C/N) ratio between 20 and 30, which is critical for efficient anaerobic digestion. In contrast, dry leaves and rice straw were found unsuitable due to their high C/N ratios. Although the impact of dry leaves and straw were noticeable in the early stages of digestion, they did not significantly contribute to the overall biogas yield.