Energy generating performance of domestic wastewater fed sandwich dual-chamber microbial fuel cells
- Authors: Adeniran, Joshua Adeniyi
- Date: 2015-06-26
- Subjects: Waste products as fuel , Water - Purification - Membrane filtration , Water - Purification - Biological treatment , Sewage - Purification - Anaerobic treatment , Microbial fuel cells , Waste heat , Bioreactors
- Type: Thesis
- Identifier: uj:13627 , http://hdl.handle.net/10210/13808
- Description: M.Tech. (Civil Engineering) , This study presents work on the design and construction of three dual-chamber microbial fuel cells (MFCs) using a sandwich separator electrode assembly (SSEA) and membrane cathode assembly (MCA) for the dual purposes of energy generation from domestic wastewater and wastewater treatment. MFC1 was designed using an improvised SSEA technique (i.e. a separator electrode membrane electrode configuration, SEMEC) by gluing a sandwich of anode, membrane and a mesh current collector cathode to an anode chamber made from a polyethylene wide-mouth bottle. The reactor was filled with 1500 mL of domestic wastewater and operated on a long fed-batch mode with a residence time of 3 weeks. The reactor was inoculated with a mixed culture of bacteria present in the wastewater stream. The aim was to study the impact of wastewater COD concentration on power generation and wastewater treatment efficiency. For MFC2 and MFC 3, cathodes were constructed using the MCA technique consisting of a membrane and a mesh current collector cathode, with the anode electrode at the opposite side of stacked Perspex sections used for the anode chamber. The impact of electrode material on current production was examined in this study. For MFC2 a mesh current collector treated with polytetrafluoroethylene (PTFE) and activated carbon (AC) functioned as the cathode, while the MFC3 cathode was an uncatalyzed mesh current collector. The two reactors were both filled with 350 mL of domestic wastewater...
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- Authors: Adeniran, Joshua Adeniyi
- Date: 2015-06-26
- Subjects: Waste products as fuel , Water - Purification - Membrane filtration , Water - Purification - Biological treatment , Sewage - Purification - Anaerobic treatment , Microbial fuel cells , Waste heat , Bioreactors
- Type: Thesis
- Identifier: uj:13627 , http://hdl.handle.net/10210/13808
- Description: M.Tech. (Civil Engineering) , This study presents work on the design and construction of three dual-chamber microbial fuel cells (MFCs) using a sandwich separator electrode assembly (SSEA) and membrane cathode assembly (MCA) for the dual purposes of energy generation from domestic wastewater and wastewater treatment. MFC1 was designed using an improvised SSEA technique (i.e. a separator electrode membrane electrode configuration, SEMEC) by gluing a sandwich of anode, membrane and a mesh current collector cathode to an anode chamber made from a polyethylene wide-mouth bottle. The reactor was filled with 1500 mL of domestic wastewater and operated on a long fed-batch mode with a residence time of 3 weeks. The reactor was inoculated with a mixed culture of bacteria present in the wastewater stream. The aim was to study the impact of wastewater COD concentration on power generation and wastewater treatment efficiency. For MFC2 and MFC 3, cathodes were constructed using the MCA technique consisting of a membrane and a mesh current collector cathode, with the anode electrode at the opposite side of stacked Perspex sections used for the anode chamber. The impact of electrode material on current production was examined in this study. For MFC2 a mesh current collector treated with polytetrafluoroethylene (PTFE) and activated carbon (AC) functioned as the cathode, while the MFC3 cathode was an uncatalyzed mesh current collector. The two reactors were both filled with 350 mL of domestic wastewater...
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Design of an anaerobic biodigestion system utilizing the organic fraction of municipal solid waste for biogas production in an urban environment
- Authors: Kigozi, Robert
- Date: 2015-06-25
- Subjects: Sewage - Purification - Anaerobic treatment , Refuse and refuse disposal - Biodegradation , Biomass energy , Sustainable development
- Type: Thesis
- Identifier: uj:13613 , http://hdl.handle.net/10210/13796
- Description: M.Tech. (Chemical Engineering) , The design process was carried out in two stages: feedstock analysis and system design. Under feedstock analysis, the study investigated the amount of the organic fraction of municipal solid waste (OFMSW) generated at the study area which was situated at the University of Johannesburg’s Doornfontein Campus (UJ DFC) in downtown Johannesburg South Africa. Furthermore, the feedstock analyses involved characterisation studies on the target waste under which several laboratory tests were undertaken. The system design involved sizing of the suitable biogas digester to be used in the system applying mathematical models and feedstock parameters obtained from the feedstock analyses. Via the application of the Simple Multi-Attribute Rating (SMART) technique of multiple-criteria decision analysis (MCDA) as a decision support tool, the most preferred option of biogas plant model was selected from a list of potential alternatives available on the market. And, in addition, a suitable site around the study area was selected by applying the analytical hierarchy process (AHP) technique of MCDA. Other system components and accessories such as the piping, scrubbers and valves were sized, selected, integrated into the system and finally layout drawings were produced using Inventor computer aided drafting (CAD) Software. Furthermore, feasibility assessments were conducted on the proposed system such as energy usage assessments and economic analyses using the net present value (NPV), internal rate of return (IRR) and benefit-cost ratio (BCR) techniques...
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- Authors: Kigozi, Robert
- Date: 2015-06-25
- Subjects: Sewage - Purification - Anaerobic treatment , Refuse and refuse disposal - Biodegradation , Biomass energy , Sustainable development
- Type: Thesis
- Identifier: uj:13613 , http://hdl.handle.net/10210/13796
- Description: M.Tech. (Chemical Engineering) , The design process was carried out in two stages: feedstock analysis and system design. Under feedstock analysis, the study investigated the amount of the organic fraction of municipal solid waste (OFMSW) generated at the study area which was situated at the University of Johannesburg’s Doornfontein Campus (UJ DFC) in downtown Johannesburg South Africa. Furthermore, the feedstock analyses involved characterisation studies on the target waste under which several laboratory tests were undertaken. The system design involved sizing of the suitable biogas digester to be used in the system applying mathematical models and feedstock parameters obtained from the feedstock analyses. Via the application of the Simple Multi-Attribute Rating (SMART) technique of multiple-criteria decision analysis (MCDA) as a decision support tool, the most preferred option of biogas plant model was selected from a list of potential alternatives available on the market. And, in addition, a suitable site around the study area was selected by applying the analytical hierarchy process (AHP) technique of MCDA. Other system components and accessories such as the piping, scrubbers and valves were sized, selected, integrated into the system and finally layout drawings were produced using Inventor computer aided drafting (CAD) Software. Furthermore, feasibility assessments were conducted on the proposed system such as energy usage assessments and economic analyses using the net present value (NPV), internal rate of return (IRR) and benefit-cost ratio (BCR) techniques...
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Investigating the potential of generating electrical energy from digester carbon waste sources at ERWAT waste water treatment facilities in the Ekurhuleni District Municipality
- Authors: Mabaso, Thembeka
- Date: 2017
- Subjects: Biogas , Digester gas , Sewage sludge fuel , Sewage - Purification - Anaerobic treatment , Sewage disposal plants - South Africa - Ekurhuleni
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/271340 , uj:28857
- Description: M.Sc. (Environmental Management) , Abstract: Biogas, a renewable energy source, is generated from biomass under anaerobic treatment. Anaerobic treatment of biomass, which is usually sludge at the stage of anaerobic digestion, occurs within a vessel – also known as a digester – enclosed of air and usually has bacteria derived from the incoming waste for digestion and the production of biogas. The main objective of this study was to investigate the electrical energy potential from digester carbon waste sources utilizing analyses from the gas and a basic excel software model. For this purpose, we used selected wastewater treatment facilities of the East Rand Water Care Company (ERWAT) that had gas reservoirs and sampling points available. The GIZ/WEC model was utilized together with other WWTP-based parameters to calculate potential electricity that could be generated daily in two plants (Vlakplaats and Waterval). The size of combined heat and power (CHP) suitable for each of the WWTPs to generate power from the biogas generated was also estimated. We found four components in the biogas (CH4, CO2, traces of H2S and O2) with CH4 and CO2 being the main constituents. The concentrations of these main constituents were 30%-38% and 63%-70% for CO2 and CH4, respectively. The potential electricity calculated was on average 3 861 kWeh/day for the Vlakplaats plant and 21 777 kWeh/day for Waterval. These values change as the biogas production varies depending on the operational conditions. This study shows that future generation of electricity using biogas is achievable at these plants. Although this study is not new it clearly emphasizes the potential of biogas utilization as a cost saving incentive at the plants where analysis was conducted.
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- Authors: Mabaso, Thembeka
- Date: 2017
- Subjects: Biogas , Digester gas , Sewage sludge fuel , Sewage - Purification - Anaerobic treatment , Sewage disposal plants - South Africa - Ekurhuleni
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/271340 , uj:28857
- Description: M.Sc. (Environmental Management) , Abstract: Biogas, a renewable energy source, is generated from biomass under anaerobic treatment. Anaerobic treatment of biomass, which is usually sludge at the stage of anaerobic digestion, occurs within a vessel – also known as a digester – enclosed of air and usually has bacteria derived from the incoming waste for digestion and the production of biogas. The main objective of this study was to investigate the electrical energy potential from digester carbon waste sources utilizing analyses from the gas and a basic excel software model. For this purpose, we used selected wastewater treatment facilities of the East Rand Water Care Company (ERWAT) that had gas reservoirs and sampling points available. The GIZ/WEC model was utilized together with other WWTP-based parameters to calculate potential electricity that could be generated daily in two plants (Vlakplaats and Waterval). The size of combined heat and power (CHP) suitable for each of the WWTPs to generate power from the biogas generated was also estimated. We found four components in the biogas (CH4, CO2, traces of H2S and O2) with CH4 and CO2 being the main constituents. The concentrations of these main constituents were 30%-38% and 63%-70% for CO2 and CH4, respectively. The potential electricity calculated was on average 3 861 kWeh/day for the Vlakplaats plant and 21 777 kWeh/day for Waterval. These values change as the biogas production varies depending on the operational conditions. This study shows that future generation of electricity using biogas is achievable at these plants. Although this study is not new it clearly emphasizes the potential of biogas utilization as a cost saving incentive at the plants where analysis was conducted.
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Parametric study and economic evaluation of a simulated biogas upgrading plant
- Authors: Masebinu, Samson Oluwasegun
- Date: 2015-06-25
- Subjects: Sewage disposal plants - Biodegradation , Sewage disposal plants - Energy conservation , Sewage - Purification - Anaerobic treatment , Water - Purification - Biological treatment , Water - Purification - Membrane filtration , Sewage - Purification - Filtration
- Type: Thesis
- Identifier: uj:13616 , http://hdl.handle.net/10210/13799
- Description: M. Tech. (Chemical Engineering) , The usual target of an upgrading process using membrane is to produce a retentate stream, the product, with high CH4 concentration. This work presents a simulation of two possible membrane configurations, single stage without recycle (SSWR) and double stage with permeate recycle (DSPR), of an existing operational biogas upgrading plant. The simulation was conducted using ChemCAD and AlmeeSoft gas permeation software to investigate the performance of the configurations on product purity, recovery and required compressor power with a view to determine the optimal operational conditions for maximising the concentration of CH4 and its recovery. Thereafter, an economic assessment on the optimal configuration was conducted to determine the gas processing cost (GPC), the profitability of producing biomethane and cost-benefit of utilising biomethane as a vehicular fuel. The simulation was validated against plant data with a maximum percentage error of 2.64%. Increasing CO2 in feed reduced product recovery and purity. Increasing feed pressure and selectivity increased product recovery and purity up to the pressure limit of the membrane module. Increasing feed flow rate increased product recovery but reduces purity. In both configurations, increasing CO2 in the feed and increasing feed pressure increased the GPC. However, increasing feed flow rate reduced the GPC. The overall performance of DSPR configuration was much higher due to increased trans-membrane area available for separation. At optimal conditions, a product purity of 91% and 96% CH4 recovery was achieved from the initial plant result of 87.2% product purity and 91.16% CH4 recovery. The total compression duty was 141 kW. The GPC was $0.46/m3 of biomethane. The cumulative discounted NPV, IRR and BCR for producing biomethane was R15,240,343, 22.41% and 2.05 respectively, with a break-even in the 5th year after plant start-up considering a prime lending rate at 9%. Using CBG instead of gasoline saves 34% of annual fuel cost with a payback period of one year and three months for the cost of retrofitting the vehicle.
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- Authors: Masebinu, Samson Oluwasegun
- Date: 2015-06-25
- Subjects: Sewage disposal plants - Biodegradation , Sewage disposal plants - Energy conservation , Sewage - Purification - Anaerobic treatment , Water - Purification - Biological treatment , Water - Purification - Membrane filtration , Sewage - Purification - Filtration
- Type: Thesis
- Identifier: uj:13616 , http://hdl.handle.net/10210/13799
- Description: M. Tech. (Chemical Engineering) , The usual target of an upgrading process using membrane is to produce a retentate stream, the product, with high CH4 concentration. This work presents a simulation of two possible membrane configurations, single stage without recycle (SSWR) and double stage with permeate recycle (DSPR), of an existing operational biogas upgrading plant. The simulation was conducted using ChemCAD and AlmeeSoft gas permeation software to investigate the performance of the configurations on product purity, recovery and required compressor power with a view to determine the optimal operational conditions for maximising the concentration of CH4 and its recovery. Thereafter, an economic assessment on the optimal configuration was conducted to determine the gas processing cost (GPC), the profitability of producing biomethane and cost-benefit of utilising biomethane as a vehicular fuel. The simulation was validated against plant data with a maximum percentage error of 2.64%. Increasing CO2 in feed reduced product recovery and purity. Increasing feed pressure and selectivity increased product recovery and purity up to the pressure limit of the membrane module. Increasing feed flow rate increased product recovery but reduces purity. In both configurations, increasing CO2 in the feed and increasing feed pressure increased the GPC. However, increasing feed flow rate reduced the GPC. The overall performance of DSPR configuration was much higher due to increased trans-membrane area available for separation. At optimal conditions, a product purity of 91% and 96% CH4 recovery was achieved from the initial plant result of 87.2% product purity and 91.16% CH4 recovery. The total compression duty was 141 kW. The GPC was $0.46/m3 of biomethane. The cumulative discounted NPV, IRR and BCR for producing biomethane was R15,240,343, 22.41% and 2.05 respectively, with a break-even in the 5th year after plant start-up considering a prime lending rate at 9%. Using CBG instead of gasoline saves 34% of annual fuel cost with a payback period of one year and three months for the cost of retrofitting the vehicle.
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Anaerobic digestion process stabilisation and in-situ upgrading of a biogas system
- Authors: Masebinu, Samson Oluwasegun
- Date: 2018
- Subjects: Biochar , Biomass energy , Sewage - Purification - Anaerobic treatment , Sewage - Purification - Filtration
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/293937 , uj:31971
- Description: Abstract: Anaerobic digestion (AD) is an established organic waste management technology, producing biogas and organic fertiliser as end-products. Despite being an established technology, AD still faces key challenges, including substrate-induced instability and the requirements for the removal of carbon dioxide (CO2) from biogas. Carbon-based materials have been recently employed as stabilising agent and as adsorbent to manage some of these limitations. Biochar, a by-product from biomass pyrolysis, has been identified as a sustainable alternative material to commercial grade carbon-based adsorbent in AD. However, research on the use of biochar has mostly focused on thermophilic batch AD, without considering the biochar production conditions and how they interact with the AD process at mesophilic conditions. The microbial communities in thermophilic AD are very sensitive to any slight fluctuation in process conditions, hence, the preference for mesophilic digestion is well known. This research investigated the impact of biochar on a mesophilic operated AD process stability and the potential to produce biogas with increased concentrations of methane (CH4) in-situ towards approaching a state of biomethane. The biochar employed was derived from the slow pyrolysis of bamboo, a phytoremediation biomass, and corn stover, the agricultural residue after a harvest of corn. Based on reviewed literature, properties of biochar that favour AD stability, and increased CH4 concentration in biogas were identified and the range of the identified optimal properties were implemented in a design of experiment (DoE). A batch biochemical methane potential test was implemented within the framework of a Taguchi-based DoE. The Taguchi DoE was coupled with grey relational and principal component analyses, in order to objectively identify the optimal combination of parameters that support the aim of this research. Optimal conditions determined from the batch test were replicated in a semi-continuous two-stage experiment by using a control digester and a biochar amended digester... , D.Phil. (Mechanical Engineering)
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- Authors: Masebinu, Samson Oluwasegun
- Date: 2018
- Subjects: Biochar , Biomass energy , Sewage - Purification - Anaerobic treatment , Sewage - Purification - Filtration
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/293937 , uj:31971
- Description: Abstract: Anaerobic digestion (AD) is an established organic waste management technology, producing biogas and organic fertiliser as end-products. Despite being an established technology, AD still faces key challenges, including substrate-induced instability and the requirements for the removal of carbon dioxide (CO2) from biogas. Carbon-based materials have been recently employed as stabilising agent and as adsorbent to manage some of these limitations. Biochar, a by-product from biomass pyrolysis, has been identified as a sustainable alternative material to commercial grade carbon-based adsorbent in AD. However, research on the use of biochar has mostly focused on thermophilic batch AD, without considering the biochar production conditions and how they interact with the AD process at mesophilic conditions. The microbial communities in thermophilic AD are very sensitive to any slight fluctuation in process conditions, hence, the preference for mesophilic digestion is well known. This research investigated the impact of biochar on a mesophilic operated AD process stability and the potential to produce biogas with increased concentrations of methane (CH4) in-situ towards approaching a state of biomethane. The biochar employed was derived from the slow pyrolysis of bamboo, a phytoremediation biomass, and corn stover, the agricultural residue after a harvest of corn. Based on reviewed literature, properties of biochar that favour AD stability, and increased CH4 concentration in biogas were identified and the range of the identified optimal properties were implemented in a design of experiment (DoE). A batch biochemical methane potential test was implemented within the framework of a Taguchi-based DoE. The Taguchi DoE was coupled with grey relational and principal component analyses, in order to objectively identify the optimal combination of parameters that support the aim of this research. Optimal conditions determined from the batch test were replicated in a semi-continuous two-stage experiment by using a control digester and a biochar amended digester... , D.Phil. (Mechanical Engineering)
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Mathematical modelling for biogas production
- Authors: Matheri, Anthony Njuguna
- Date: 2016
- Subjects: Sewage - Purification - Anaerobic treatment , Sewage - Purification - Mathematical models , Renewable energy sources , Biomass energy , Biogas
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/213006 , uj:21066
- Description: Abstract: The main focus of this dissertation is the experimental, modelling and simulation of anaerobic digestion processes from pilot bio-digesters. For this purpose, biochemical kinetic models were utilized together with corresponding simulation software; DYNOCHEM. By application of the anaerobic digestion (AD), different parameters have been investigated and simulated including adjustments of the process model and corresponding modifications. To validate the process model, the modelled data was compared with experimental monitored laboratory results. Bio-chemical kinetics modelling was applied as a systematic tool in order to support the process design and optimization of a demonstration of the biogas processes which constitutes the main scientific framework and background of this dissertation. Monitored laboratory-scale biogas production data were used for parameter calibration in order to predict plant performance. The calibration focused on the influent characterization of both substrates and on selection of kinetic of the coefficients in order to generate a uniform set of parameters which are applicable for the simulation of codigestion. In this study, it was observed that the experiment work under laboratory scale using conventional bio-methane potential (BMP) analyzers under mesophilic optimum temperature of 35 oC and 37 oC, and pH of 7 for co-digestion of organic fraction of municipal solid waste (OFMSW) with cow dung and manure with grass clippings. The substrate characterization moisture content ranged from 60-95%, volatile content 55-95%, total solid 10-90% and carbon to nitrogen ratio 16-20 for manure and 5-15 for OFMSW. All trace elements concentration were below the threshold of 32 mg/l that leads to inhibition of micro-organisms activity. The rate of conversion increased with retention time. According to the findings, 54-62% of methane composition was evaluated. The kinetics constant evaluated ranged from 0.009-0.35 d-1 and coefficient of determination (R2) ranged from 0.9989-0.9998. The Michaelis-Menten and Monod models provided goodness of fit of 0.9997 with confidential level of 95%. The simulations confirmed that the rate of conversion increased as temperature increases and conversion of reactants increased with retention time, until an equilibrium state was reached. The AD process modelling using DYNOCHEM was successfully modified and implemented to account for unsteady operation which is generally the case of full-scale reactor by developed methodology. , M.Tech. (Chemical Engineering)
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- Authors: Matheri, Anthony Njuguna
- Date: 2016
- Subjects: Sewage - Purification - Anaerobic treatment , Sewage - Purification - Mathematical models , Renewable energy sources , Biomass energy , Biogas
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/213006 , uj:21066
- Description: Abstract: The main focus of this dissertation is the experimental, modelling and simulation of anaerobic digestion processes from pilot bio-digesters. For this purpose, biochemical kinetic models were utilized together with corresponding simulation software; DYNOCHEM. By application of the anaerobic digestion (AD), different parameters have been investigated and simulated including adjustments of the process model and corresponding modifications. To validate the process model, the modelled data was compared with experimental monitored laboratory results. Bio-chemical kinetics modelling was applied as a systematic tool in order to support the process design and optimization of a demonstration of the biogas processes which constitutes the main scientific framework and background of this dissertation. Monitored laboratory-scale biogas production data were used for parameter calibration in order to predict plant performance. The calibration focused on the influent characterization of both substrates and on selection of kinetic of the coefficients in order to generate a uniform set of parameters which are applicable for the simulation of codigestion. In this study, it was observed that the experiment work under laboratory scale using conventional bio-methane potential (BMP) analyzers under mesophilic optimum temperature of 35 oC and 37 oC, and pH of 7 for co-digestion of organic fraction of municipal solid waste (OFMSW) with cow dung and manure with grass clippings. The substrate characterization moisture content ranged from 60-95%, volatile content 55-95%, total solid 10-90% and carbon to nitrogen ratio 16-20 for manure and 5-15 for OFMSW. All trace elements concentration were below the threshold of 32 mg/l that leads to inhibition of micro-organisms activity. The rate of conversion increased with retention time. According to the findings, 54-62% of methane composition was evaluated. The kinetics constant evaluated ranged from 0.009-0.35 d-1 and coefficient of determination (R2) ranged from 0.9989-0.9998. The Michaelis-Menten and Monod models provided goodness of fit of 0.9997 with confidential level of 95%. The simulations confirmed that the rate of conversion increased as temperature increases and conversion of reactants increased with retention time, until an equilibrium state was reached. The AD process modelling using DYNOCHEM was successfully modified and implemented to account for unsteady operation which is generally the case of full-scale reactor by developed methodology. , M.Tech. (Chemical Engineering)
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Studies on the improvement of biogas production from anaerobic digestion of animal wastes
- Authors: Sebola, Mmabyalwa Rebecca
- Date: 2015
- Subjects: Biogas , Sewage - Purification - Anaerobic treatment , Renewable energy sources , Biomass energy
- Language: English
- Type: Master’s Thesis
- Identifier: http://hdl.handle.net/10210/57296 , uj:16377
- Description: Abstract: The unsustainability of intensive reliance on fossil fuels and none-renewable resources as the main sources of energy, frequent rises in energy prices, the need for climate change mitigation and environmental protection have intensified the need for green energy. In this respect, green energy, in the form of biogas, has gained increased attention as a cost effective and environmentally cautious approach. This dissertation presents various studies aimed at improving the biogas production from anaerobic digestion of animal wastes. The experiments were conducted using the batch scale mesophilic tests. Characterisation studies (ultimate and proximate analysis) were conducted to identify key characteristics of the selected feedstocks. In addition, an economic assessment on the feasibility of anaerobic technology was conducted. The waste had average moisture content (MC) ranging from 7 – 34% and 70 – 81% for the dry and wet samples, respectively. The average volatile matter (VM) varied between 44 – 58% with the C/N for CD, CM, PM and SW being 26.20, 8.13, 17.64 and 8.57, respectively. Decreasing the particle size of the feedstock increased the amount of biogas significantly by increasing the total surface area of the material exposed to the anaerobic microbes. At optimal particle size (25μm), methane production was 3 – 30 % higher as compared to that of 100μm and above. Highest methane yields were achieved from CD to CM, PM and SW at ratio of 1:1:1:1. At optimum temperature (40˚C), the highest methane yield (62% CH4/ d) was obtained on Day 6. Adding 50% VS resulted in more methane yields (64% CH4/d) than 30 and 40%. An introduction of 40% recycled liquid and 60% fresh water to the digester gave the best performance, with 73% CH4/d of biogas produced within 5 days. Soaking the feedstock prior digestion improved both the methane and biogas yields and stability of the process. An economic evaluation over a period of 5 years with 8 hours daily operation and a breakeven of 1.5 years was assessed. The proposed model has debt repayments of R 2,478,551 with the total revenue from years 2 – 5 being R 2,360,800, R 2,930,158, R... , M.Tech. (Chemical Engineering)
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- Authors: Sebola, Mmabyalwa Rebecca
- Date: 2015
- Subjects: Biogas , Sewage - Purification - Anaerobic treatment , Renewable energy sources , Biomass energy
- Language: English
- Type: Master’s Thesis
- Identifier: http://hdl.handle.net/10210/57296 , uj:16377
- Description: Abstract: The unsustainability of intensive reliance on fossil fuels and none-renewable resources as the main sources of energy, frequent rises in energy prices, the need for climate change mitigation and environmental protection have intensified the need for green energy. In this respect, green energy, in the form of biogas, has gained increased attention as a cost effective and environmentally cautious approach. This dissertation presents various studies aimed at improving the biogas production from anaerobic digestion of animal wastes. The experiments were conducted using the batch scale mesophilic tests. Characterisation studies (ultimate and proximate analysis) were conducted to identify key characteristics of the selected feedstocks. In addition, an economic assessment on the feasibility of anaerobic technology was conducted. The waste had average moisture content (MC) ranging from 7 – 34% and 70 – 81% for the dry and wet samples, respectively. The average volatile matter (VM) varied between 44 – 58% with the C/N for CD, CM, PM and SW being 26.20, 8.13, 17.64 and 8.57, respectively. Decreasing the particle size of the feedstock increased the amount of biogas significantly by increasing the total surface area of the material exposed to the anaerobic microbes. At optimal particle size (25μm), methane production was 3 – 30 % higher as compared to that of 100μm and above. Highest methane yields were achieved from CD to CM, PM and SW at ratio of 1:1:1:1. At optimum temperature (40˚C), the highest methane yield (62% CH4/ d) was obtained on Day 6. Adding 50% VS resulted in more methane yields (64% CH4/d) than 30 and 40%. An introduction of 40% recycled liquid and 60% fresh water to the digester gave the best performance, with 73% CH4/d of biogas produced within 5 days. Soaking the feedstock prior digestion improved both the methane and biogas yields and stability of the process. An economic evaluation over a period of 5 years with 8 hours daily operation and a breakeven of 1.5 years was assessed. The proposed model has debt repayments of R 2,478,551 with the total revenue from years 2 – 5 being R 2,360,800, R 2,930,158, R... , M.Tech. (Chemical Engineering)
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