What is biogas?
Biogas is the gas generated as a result of the microbial activities of anaerobic microorganisms in the absence of oxygen that use organic matter to regenerate and produce energy at specific conditions of pH, hydraulic retention time, temperature, carbon and nitrogen rate (C/N), etc. Biogas is the bioenergy produced from all kind of biomass sources. Typically biogas is composed of 50-75% of methane (CH4), 30-40% of carbondioxide (CO2) and 1-3% of water vapor, ammonia, hydrogen sulfide or nitrogen. Biogas has a calorific value between 21-24 MJ/m3 or 6 kWh/m3.
How is biogas generated?
Biogas generation occurs at the end of 3 or 4 steps of anaerobic degredation. These steps are called: hdyrolysis, acidogenesis, acetogenesis and methanogenesis which of all take place after eachother respectively.
Hydrolysis is the breakdown of the organic matter (protein, carbohydrate, cellulose, fat) into water soluble monomers with the help of exoenzymes (cellulase, cellobiase, xylanase, amylase, lipase, and protease) of facultative bacteria. These monomers are short chain carbohydrates, amino acids, fatty acids and glycerine Then, water soluble monomers are further degraded to hydrogen (H2), carbondioxide (CO2), ammonia (NH3) and short chain organic acids or volatile fatty acids that has one to five carbon atoms in the molecule structure as butyric acid, propyonic acid, acetic acid, and also alcohols in the acidogenic phase by fermentative bacteria. Acetogenic phase is the conversion of short chain VFAs, CO2 and H2 into acetate or acetic acid by acetogenic microorganisms. Finally methanogenesis produces methane by two groups of methanogenic bacteria which one of them splits acetate into methane and carbon dioxide and the other one uses hydrogen as electron donor and carbon dioxide as acceptor to produce methane.
What is biogas used for?
Biogas is used in many areas of life and technology. Generally biogas is used for cooking in households, heating households, lighting or electricity generation in CHP units. Larger amounts of biogas can be feed to the into gas supply networks. Also biogas can be used as fuel for vehicles following biogas upgrading.
What kind of wastes can be used for biogas production?
All kinds of carbohydrates, protein, fat, cellulose, hemicellulose and lignine can be used for biogas production. These specific wastes are found in industrial (forestry, agricultural, textile, leather, paper, food, sugar) wastes, all kinds of vegetable and fruit wastes, garden wastes, wheat and fat wastes, all kinds of animal wastes, household wastewater and solid wastes, and wastewater treatment sludges.
What kind of wastes can be used for biogas production?
All kinds of carbohydrates, protein, fat, cellulose, hemicellulose and lignine can be used for biogas production. These specific wastes are found in industrial (forestry, agricultural, textile, leather, paper, food, sugar) wastes, all kinds of vegetable and fruit wastes, garden wastes, wheat and fat wastes, all kinds of animal wastes, household wastewater and solid wastes, and wastewater treatment sludges.
References
1-Deublein, D., Steinhauser, A., Biogas:From Waste And Renewable Energy Resources, Wiley-Vch Verlag GmbH Co. & KGaA, Weinheim, ISBN 978-3-527-31841-4, 2008.
2-Weiland, P., Biogas production: current state and perspectives, Applied Microbiology and Biotechnology, 85:849–860, 2010.
3-Appels L., Baeyens J., Degreve J., Dewil, R., Principles and potential of the anaerobic digestion of waste-activated sludge, Progress in Energy and Combustion Science 34 : 755–781, 2008.
4-Bond, T., Templeton, M.R., History and future of domestic biogas plants in the developing world, Energy for Sustainable Development 15 : 347–354, 2011.
1-Deublein, D., Steinhauser, A., Biogas:From Waste And Renewable Energy Resources, Wiley-Vch Verlag GmbH Co. & KGaA, Weinheim, ISBN 978-3-527-31841-4, 2008.
2-Weiland, P., Biogas production: current state and perspectives, Applied Microbiology and Biotechnology, 85:849–860, 2010.
3-Appels L., Baeyens J., Degreve J., Dewil, R., Principles and potential of the anaerobic digestion of waste-activated sludge, Progress in Energy and Combustion Science 34 : 755–781, 2008.
4-Bond, T., Templeton, M.R., History and future of domestic biogas plants in the developing world, Energy for Sustainable Development 15 : 347–354, 2011.
