IJCRR - 4(19), October, 2012
Pages: 197-201
Date of Publication: 15-Oct-2012
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ANALYSIS OF DRY ANAEROBIC DIGESTION OF COW DUNG WITH RESPECT TO WET ANAEROBIC DIGESTION ON BIOGAS PRODUCTION
Author: Pradeep Kumar Uppal, Shailendra Jain, Rajkumar Bhatia
Category: Technology
Abstract:Anaerobic digestion is an effective way to covert the animal manure in to profitable byproducts as well as reduce the pollution of water, air and soil caused by these wastes. Dry anaerobic digestion has been considered as suitable process for potential renewable energy, recovery with nutrient rich fertilizer and sustainable solid waste management. It saves the water and can be done in less space as compare to the wet anaerobic digestion which requires the large space for drying the effluent manure and it also requires the large amount of water during feeding. During the process of dry anaerobic digestion 150L water is required in comparison with wet anaerobic digestion where 2500 Liters water is required for the same amount of production of biogas production. Dry solid consistency is 12.5 - 15%. Dry anaerobic digestion helps in improving ground water as well as wet digestion process requires drying in pits that results in leach out soil and increase its contamination. The digested cow manure in dry stage shall contain rich nutrients and removed in mechanized way and would be ready for use in field without dewatering. While wet anaerobic process require more space, time and difficulty in handling digested cow manure in slurry form.
Full Text:
INTRODUCTION
The dry anaerobic digestion organic matter is an appropriate technology for recovery of energy with nutrient rich fertilizer and sustainable waste management. The green house gas produced by the other methods of decomposition such as land filling, anaerobic composting etc. produces the pollution in atmosphere. The anaerobic digestion of cow dung (organic matter) produces the biogas that contain methane and suitable to use as fuel for useful gain. In the absence of Oxygen anaerobic microbes such as, methanogenic bacteria, acetogenic bacteria, fermentative bacteria digest biodegradable material and process bio gas. The anaerobic digestion of organic material basically follows: hydrolysis, acidogenesis, acetogenesis and methanogenesis. The conversion process begins with bacteria hydrolyzing complex organic polymers such as carbohydrates, proteins, lipids and fats, into simple monomeric carbohydrates, amino acids, sugars and long chain fatty acids. The reduced compounds are then converted by fermentative bacteria into a mixture of short chain volatile fatty acids (VFA5) and other minor products such as carbon dioxide, hydrogen and alcohol. These organic acids are further breakdown during acetogenesis to acetate, carbon dioxide, and hydrogen. In the final stage, methanogenesis takes place by two groups of bacteria: acetoclastic and hydrogenotrophic methanogens. Acetoclastic methanogens split acetate into methane and carbon dioxide (of the order of nearly 40%) while hydrogenotrophic methanogens uses hydrogen as electron donor and carbon dioxide as electron acceptor to produce methane of the order of nearly 60%. Advantages of dry anaerobic treatment when compared to liquid anaerobic digestion: higher organic loading rate, lower energy requirements for heating, less process energy for stirring, reduced nutrient run off during storage and distribution of residues and limited environmental consequences. In addition, De Baere stated that, dry anaerobic processes have a more energetically• effective performance since they require less pretreatment and added water. Mainly due to its reduced cost in digesters and slurry handling problems, the dry anaerobic digestion process has attracted increased attention all around the world recently. However, the high-solids anaerobic digestion is known to suffer from many inhibition problems and the process is also harder to control.
MATERIAL AND METHODS
The manure is collected from the "GOSHALA" is feeded in Continuous Stirrer Tank Reaction (CSTR) on dry basis and in KVIC biogas plant on wet basis (1 part water + 1 part manure).
Characteristics of Feed Stock :
The study was conducted by evaluate the mesophillic dry anaerobic digestion of undiluted and unscreened cow manure in CSTR and same cow manure is feeded under the same
Analytical Methods:
The parameter analyzed were pH, TS and VS. All the analytical determinations were performed according to the standard methods. The pH of the mixture was measured with the digital pH meter. The yielded biogas was determined by closing the outlet value then in a given time how much floating dome rises in dry (CSTR) as well as in wet (KVIC) anaerobic digestion. Dry solids are measured by heating the sample in over for 4 hour at 105ºC and its weight is measured and again it is kept in oven for next 4 hour at 105°C and its weight is measured. The process is repeated till the weight for each repetition becomes same. The VS is measured by burning the dry solid in oven at 550°C for 6 hours.
OBSERVATION AND RESULTS
The cow manure properties are determined in raw state and after the anaerobic digestion for CSTR (Dry anaerobic digestion) and KVIC model (wet anaerobic digestion) for one month with twice a week frequency. The following results are obtained.
Since the basic material in both digester are same, so the percentage of volatile solids are same but the dry solids are different due to addition of water in wet anaerobic digestion the water content is more and percentage of dry solids are less. In KVIC digester the loss of energy is more due to addition of water so the difference of temperature of digested manure is always nearly 2°C less than the digested manure of CSTR (dry digestion).
CONCLUSION
Comparison between KVIC digester and high rate methanization (CSTR) diagester.
Dry anaerobic digestion is considered superior option for Bio-gas production as compared to wet anaerobic digestion in view of environment. Dewatering and drying effluent manure is not required. Saves process water which otherwise leads to different environmental problems. This process saves the space and it is economically viable.
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