Roles of Microorganisms in Anaerobic Digestion and Biogas Production
Anaerobic digestion is a biological process in which microorganisms break down organic matter without oxygen and transform them into end-products, including biogas, an energy-rich gas comprised of methane (CH4), carbon dioxide (CO2), and other trace amounts of gases. Anaerobic digestion can be summarized as a four-stage process (1) hydrolysis, (2) acidogenesis, (3) acetogenesis, and (4) methanogenesis, where limited groups of microorganisms function in each phase which is why the microorganism balance and diversity are crucial to keeping the whole process steady and effective.
Hydrolysis and Acidogenesis
As a result of the reaction of chemicals to water, known as the process of hydrolysis, proteins, cellulose, and other carbohydrates are quickly broken down into soluble compounds. Any remaining dissolved oxygen, ferric iron, sulfate, etc., are used as electron acceptors of hydrolytic bacteria in the first stage of anaerobic digestion. Acidifying bacteria then convert the produced soluble compounds into volatile fatty acids (VFAs), hydrogen, and CO2. As the electron acceptors are used up, fermentation processes take over. Bacteria, usually Clostridia, Pseudomonas, and Bacilli, which are obligate and facultative anaerobes, perform these processes.
Acetogenesis and Methanogenesis
These two latter stages are closely connected. This stage involves the conversion of the organic acids into acetic acid, CO2, and hydrogen by several groups of bacteria, including Clostridia and Desulfovibrio. The by-products of acetogenesis serve as the substrates for methanogenic bacteria. Various pathways take place during the final phase, methanogenesis. Methanogens convert the intermediate organic products from the previous processes to CH4. Acetolactic methanogens generate about 70% of CH4 by utilizing acetate and methyl compounds, while hydrogen-oxidizing methanogens produce the remaining 30% (e.g., Methanosarcina barkeri and Methanomethylovorans hollandica) from CO2 and hydrogen.
The group and strains of bacteria mentioned above are found in Microbe-Lift/IND series. Microbe-Lift contains selected and formulated specialized microorganisms that speed up the biological degradation of organic matter in anaerobic digesters.
Benefits:
- Acceleration of biogas generation
- Increase in methane contents
- Minimization of sludge and solid build-up
- Hydrogen sulfide reduction
- Improvement of effluent quality
The attached file provides an insight into how Microbe-Lift products improve anaerobic digester efficiency and biogas generation.
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