Biological methanogensis, carried out by a mixed culture of bacteria, is an exceedingly common and widespread process in nature. Methane is produced in the soil, in peat bogs, in both fresh-water and marine sediments, in sanitary landfills, and in the anaerobic digesters used to dispose of sludge in sewage plants. Yet the process requires a rather specific set of environmental conditions, including the presence of suitable energy-yielding substrates, the usual nutrient elements, a pH near neutrality, a low Eh, and a sufficiently low concentration of inhibitory compounds. Substances found to be inhibitory include organic acids, ammonia, certain heavy metals, sulfide, sulfate and nitrate. Why, then, does the process appear to take place, sooner or later, whenever naturally occurring organic matter decays under anaerobic conditions? The answers appear to be in the realm of microbial ecology. Microorganisms widely distributed in nature alter the environment in such a way that the growth of methanogenic bacteria eventually is assured. Methanogenesis then proceeds until substrate exhaustion.
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- Biological Methanogenesis in Sediments and Sanitary Landfills
D. M. Updegraff
- Springer Berlin Heidelberg