1. Biological process of anaerobic digestion of organic matter

During the anaerobic digestion process, the conversion of complex organic compounds into methane and carbon dioxide is achieved by the complementary action of microorganisms belonging to a taxonomically and functionally complex microbial community. The more complex the chemical substances to be degraded, the greater the number of interacting microbial species. The simplified model developed by Zeikus (1980) to describe the anaerobic digestion process is widely accepted; it comprises four stages, carried out by different microbial groups (figure