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Impact of Different Factors on Biogas Production in Poultry Dropping Based Biogas Plants of Bangladesh

Mohammad Shariful Islam
Electrical & Electronic Engineering, Bangladesh University of Engineering & Technology (BUET), Dhaka, Bangladesh

Asif Islam
asif038@gmail.com
Planning & Development Division, Power Grid Company of Bangladesh (PGCB) Ltd., Dhaka, Bangladesh

Dipendra Shah
dipendrashah@gmail.com
NIS Department, Huawei Technologies Co. Ltd., Kathmandu, Nepal

Enamul Basher
enamul_basher@eee.buet.ac.bd
Electrical & Electronic Engineering, Bangladesh University of Engineering & Technology (BUET), Dhaka, Bangladesh

Abstract/ Executive Summary:

Bangladesh, with poultry farms number of 215000 and poultry population of 200 million, has a potential of 1.33TWhr electricity per year. Despite of this huge potential, only few number of biogas plants have been deployed till date. Besides, most of these plants are unable to produce the expected amount of biogas as most of the digesters of these plants are made locally and they don’t have any scheme for monitoring and controlling temperature, pH, bacterial population in digester, mixture of different substrate, hydraulic retention time, total solid (TS), periodic agitation, periodic loading and unloading of substrate etc. But, there is few bigger size plants which contain imported digesters equipped with monitoring and controlling schemes, hence they produce bigger amount of biogas. In this study, an analysis has been done focusing the impacts of above mentioned factors on biogas production by comparing biogas production between locally made digesters and imported digesters. The result reveals that up to 75% more biogas is generated in imported digesters than the locally made digesters.

Keywords: Digester, Anaerobic Digestion, Psychrophilic, Mesophilic, Thermophilic, Hydraulic Retention Time

Location: Gaziupur, Mymensingh, Rangpur, Sylhet and Panchagarh district, Bangladesh

Start Date:

End Date:

Program Area: Crop-Soil-Water Management

Commodity: Bio-gas, Poultry

Objectives:

To reveal the influence of these factors on biogas production in biogas plants deployed in poultry farms.

Methodology:

For technical and economical success insuring stability process and maintaining required quality and quantity of gas is a prerequisite. To maintain these prerequisite following conditions must always be fulfilled: * Anaerobic condition in the digester must be maintained. * Temperature must me controlled to the permissible values. * Availability of nutrients for bacteria; * Substantial amount of nutrients bacteria must always be present in the digester. * Substrate must be loaded and unloaded periodically. * C/N ration must always be observed and work accordingly. * Correctly chosen proportion of solids content and proper agitation; * Absence of inhibitors of the digestion process. Temperature: Temperature has the most pronounced impacts on anaerobic digestion. It has three main temperature ranges: from 10-25°C (psychrophilic conditions), from 30-37°C (mesophilic conditions) and from 48-55°C (thermophilic conditions) [13]. Psychrophilic digestion process is very slow hence only mesophilic and thermophilic digestion processes are used in practice. At very low or high temperature the activities of bacteria population is almost stopped consequently the digestion process is becomes very long. Hence the production of biogas is reduced. The methane content becomes very low. As a result the produced biogas cannot be used as fuel for electricity generation and cooking. pH Value: The pH of the digester is a function of the concentration of volatile fatty acids produced, bicarbonate alkalinity of the system, and the amount of carbon dioxide produced. The optimum range of pH for biogas production is between 7.0 and 7.2. But the substantial biogas can be produced for the pH range of 6.6 to 7.6. Biogas production reduces many fold for the pH value of less than 5 as the bacteria population decrease significantly under the circumstances. Bacterial Population in Digester: Digester must always contain a certain amount of bacteria for acceptable amount of biogas production. Any dip in bacteria population impedes the production of biogas. Addition of enzymes enhances the bacteria population which in turns increases biogas production Mixture of Different Substrates: As different substrate produce different amount of biogas, the mixture of them increases the biogas production and methane content. Hydraulic Retention Time (HRT): The Hydraulic retention time (HRT) is also known as hydraulic residence is the time required for complete digestion of the substrates in Digester. Hydraulic retention time is the volume of the digester divided by the influent flow rate. HRT = Volume of Digester / Influent Flow Rate where using SI UnitsVolume is in [m³] and Influent flow rate is in [m³/h]. HRT is usually expressed in hours (or sometimes days). Total Solid (TS) Total solid contained in a certain amount of materials is usually used as the material unit to indicate the biogas producing rate of the materials. Most favorable TS value desired is 8%. Daily Substrate Input The daily substrate input depends on the HRT of the digestion process. The HRT can be 10 days to 80 days. If digester HRT is 10 days, than daily substrate load will be 1/10 from the overall volume of substrate in digester. For biogas plants working in thermophilic range, daily substrate load can constitute up to 1/5 of overall substrate volume in digester. Substrate Digestion: Time Choice of substrate digestion time depends also from the type of substrate used. Cattle substrate takes 10-15 days, pig manure 9-12 days, poultry manure 10-15 days and 40-80 days manure mixed with vegetation waste for complete digestion. C/N Ratio: For optimal C/N ratio different substrates are mixed for which maximizes the production of biogas. Regular Agitation: For maximizing the production of biogas regular agitation of substrate in digester is required. The regular agitation frees the produced biogas entrapped in the substrate, mixes the fresh substrate with bacteria population, prevents scum and sediment, prevents temperature gradient inside the digester, provides the homogeneous mixture of bacteria population and prevents the formulation of voids. In Bangladesh two types of digesters are used for biogas production in poultry farms. The large portions of these digesters are locally produced and are used for smaller size of biogas plants. But in larger size of plants the digesters are imported from abroad. Only 3 plants are using mixing tanks, all of them are of PPL. Most of them are using 1 digester, but Rangpur is using 4 digesters and Gaziupur using 2 digesters. Only three are using separate holding tanks and only two of them are using how water tank for temperature control..

Source of Information: Journal of Energy and Natural Resources, 2013; 2(4): 25-32

Article Link (Online Journal): doi: 10.11648/j.jenr.20130204.11

Funding Source:

Budget:

Total Budget (Tk.) :

Achievement/Findings:

This research work represents the impact of different factors on production of biogas in different biogas plants of Bangladesh. The operation of different size of biogas plants throughout the country starting from 6.4 m3 to 4000 m3 have been analyzed in this paper. The impacts of temperature, pH, agitation periodic loading and unloading on biogas yield are analyzed based on the collected data from survey, internet and other sources. It has been found that most of the biogas plants don’t have the schemes for controlling the temperature, pH, agitation, loading and unloading apart from few of the biogas plants which are imported. These imported biogas plants are well equipped to control temperature, pH, agitation, loading and unloading etc. Hence they produce up to 75% more biogas than the locally produced biogas plant. But for locally produced biogas plants additional controlling schemes can be provided making an additional investment. Although providing controlling schemes incurs additional costs but the increment in gas production suppresses the costs and the capital cost for per unit of electricity generation decreases by up to 38%.

Knowledge Management: Journal