Progress and Recent Trends in Biogas Processing

In this study, progresses and recent trends in biogas processing are reviewed. Biogas is generated from biomass by digestion under anaerobic conditions in the presence of microorganisms. Anaerobic digestion occurs in the absence of air and is typically carried out for a few weeks. The anaerobic digestion process occurs in the following four basic steps: (1) hydrolysis, (2) acidogenesis, (3) acetogenesis, and (4) methanogenesis. In the last two decades, anaerobic digestion technology was significantly improved by the development of the sludge bed digesters, granular sludge-based bioreactors such as the upflow anaerobic sludge blanket, and the anaerobic hybrid reactor. Biogas plants at farm level are good candidates for treating organic residues of both municipalities and the agro-industrial sector in a cost-effective way and in providing territorially diffused electric and thermal power.