Microbial Anaerobic Digestion (Bio-Digesters) as an Approach to the Decontamination of Animal Wastes in Pollution Control and the Generation of Renewable Energy

Abstract

With an ever increasing population rate; a vast array of biomass wastes rich in organic and inorganic nutrients as well as pathogenic microorganisms will result from the diversified human, industrial and agricultural activities. Anaerobic digestion is applauded as one of the best ways to properly handle and manage these wastes. Animal wastes have been recognized as suitable substrates for anaerobic digestion process, a natural biological process in which complex organic materials are broken down into simpler molecules in the absence of oxygen by the concerted activities of four sets of metabolically linked microorganisms. This process occurs in an airtight chamber (biodigester) via four stages represented by hydrolytic, acidogenic, acetogenic and methanogenic microorganisms. The microbial population and structure can be identified by the combined use of culture-based, microscopic and molecular techniques. Overall, the process is affected by bio-digester design, operational factors and manure characteristics. The purpose of anaerobic digestion is the production of a renewable energy source (biogas) and an odor free nutrient-rich fertilizer. Conversely, if animal wastes are accidentally found in the environment, it can cause a drastic chain of environmental and public health complications.

A Review of the Chemistry of Anaerobic Digestion: Methods of Accelerating and Optimizing Process Efficiency

“…Bacteria under anaerobic conditions thrive in a broad range of temperatures that can be divided into two broad categories; namely mesophilic and thermophilic temperatures. The former refers to medium-temperature range where the bacteria thrives in the temperature range 20-45 • C (68-113 • F), while the later refers to high-temperature range where bacteria activity increases for optimum gas production, and can be achieved between 49 and 57 • C (120-135 • F); nonetheless, when temperature is kept within these ranges and with constant feedstock supply, the production of CH 4 can be maximized [60].…”

Water-Related Impacts of Climate Change on Agriculture and Subsequently on Public Health: A Review for Generalists with Particular Reference to Pakistan

“…Manure and animal waste contains pathogens, veterinary pharmaceuticals, and nutrients along with heavy metals, which are transported and spread into the environment, ultimately causing both environmental and human health hazards [37]. More intense storms due to climate change cause these contaminants to run-off and ultimately to enter the human food chain.…”

“…Animal waste can also be used as an alternative source of energy. Therefore, anaerobic digestion of animal waste could be applied for the production of biogas, and different methanogens can enhance the process of digestion [37]. …”

Cadmium Addition Effects on Anaerobic Digestion with Elevated Temperatures

“…Lignocellulosic biomass wastes, which are being generated in large amounts annually, can be used as an energy resource by sustainable technologies, such as anaerobic digestion [1][2][3]. The digestion microorganism in the reactors requires a trace amount of certain metals for optimal growth and performance [4]. In the past decades, the impacts of cadmium (Cd) on anaerobic digestion received great attention since it is a metal of major environmental and human concern [5][6][7][8].…”