Bio-Methane Production from Wastes: Focus on Feedstock Sources and Microbial Communities

Abstract

The anaerobic digestion process is a proven microbially mediated technology to achieve the reduction of organic wastes with simultaneous production of biogas. The number of biogas plants is continuously increasing worldwide. In Asia, millions of family produce biogas for domestic use by means of their own small-scale digesters. A number of new biowaste-based feedstocks are currently investigated as well as the efficacy of different substrate mixtures. During anaerobic digestion, biomass is degraded by microorganisms belonging to different functional groups performing their task through three sequential stages: hydrolysis and acetogenesis dominated by Bacteria and methanogenesis carried out by Archaea. A stable and efficient process relies heavily on the concerted and syntrophic activity of these microorganisms. During the last years, the application of culture-independent molecular techniques to samples from various anaerobic digesters has provided significant insights into these complex microbial communities revealing higher diversity at phylogenetic and functional level of bacterial communities than the archaeal ones. Greater efforts are needed to gain insights into the phylogeny, interspecies interactions, and function of key microorganisms involved in the first steps of anaerobic digestion as these details can provide the opportunity for enhancing methane yields through a more efficient production of substrates for methanogenesis.