Microbial anaerobic digestion: process dynamics and implications from the renewable energy, environmental and agronomy perspectives

Microorganisms have been allied with serious deleterious environmental, human and public health hazards. Microbial interactions are vital in the biotransformation of wastes to valuable end products via the waste-to-energy technology. Microbial anaerobic degradation has been considered as a powerful tool to address the shortcomings faced by conventional energy sources (e.g. the conventional energy sources are non-renewable, can deplete over time and are very costly). It is the anaerobic breakdown of organic wastes within the precincts of an airtight biodigester, by the concerted activities of four metabolically linked microorganisms participating at specific phases of the process to ultimately yield methane and carbon dioxide. Microorganisms are present in these wastes from animal origin, feeds or during collection of the wastes for disposal. The threefold benefit of the process includes: firstly, sanitization of the organic wastes whereby the pathogens of environmental and public health significance can be reduced to threshold levels recommended for safe handling by humans. Also, it addresses the pollution problem caused by greenhouse gas emission. Secondly, the recovered digestate contains macro- and micronutrients that are valuable for plant growth. Soil amendment with digestate influences the microbial activity, the microbial biomass structure and the size which in turn improve on soil fertility and quality thus, improve on food security. Clearly, this minimizes the use of synthetic chemical fertilizers with adverse effects. Thirdly, anaerobic digestion of biomass generates biogas, a renewable energy from waste degradation which can be used for cooking, heating and or harnessed to produce electricity.