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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Potential for producing sustainable energy from bio-waste through thermal decomposition
- Authors: Manala, Cecil Khosi
- Date: 2017
- Subjects: Waste products as fuel , Refuse and refuse disposal , Biomass energy , Decomposition (Chemistry)
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/280125 , uj:30095
- Description: M.Ing. (Mechanical Engineering) , Abstract: Energy in its different forms is an important asset to man‟s day-to-day activities from general house hold applications such as cooking and heating to large scale industrial applications such as power generation. However, the current reliance on fossil fuel based energy has become a central concern with respect to sustainable development. Fossil fuels are associated with greenhouse gas emissions and global warming which have been attributed to the dramatic weather and climate change patterns on the planet today posing significant threat to life e. There is, therefore, a need to find more sustainable sources of energy for the planet. Biomass based energy has been used by humanity as a primary source of energy long before the episode of fossil fuel usage. Harnessing of this form of energy has become of overwhelming interest largely due to global warming. It has also been realized that producing renewable energy locally can offer a viable alternative, and facilitate socio-economic development in communities as evidenced by several sustainable energy production projects around South Africa. Biomass contributes 14% of the World‟s primary energy supply. About 75% of its usage is in developing countries. In this work, the organic fraction of municipal solid waste (OFMSW) was quantified at a landfill site in Johannesburg. This was part of a wider project to produce biogas from municipal waste. The potential of that waste to produce syngas by thermal decompositions needs to be investigated as an alternative to anaerobic bio digestion. Furthermore, a bamboo species known as bambusa lacooa, which is currently being introduced for mine dumps rehabilitation in South Africa, was identified as a potential syngas production feedstock. If bamboo based mine dump rehabilitation succeeds, the economic value of the then widely available bamboo needs to be investigated. Production of syngas by pyrolysis becomes one such economic value chain. The aim of this work was therefore to investigate the optimum production of syngas from OFMSW and bamboo by pyrolysis. Specimens of these materials were prepared for thermal decomposition. Bamboo was categorised into wet and dry bamboo and dried in the sun for a period of 14 days. OFMSW made up of mixed food waste was collected from the waste dump landfill site and dried in the sun for a period of 24 hours. The candidate bio-waste materials were subjected to thermal decomposition in a specially designed pyrolysis reactor. Fumes produced during the thermal decomposition were collected at 100˚C temperature intervals from 0 ˚C to 700 ˚C. Dry bamboo produced the highest yield quality of syngas (24% - 23% quality) between 200 ˚C and 400 ˚C. Wet bamboo produced lower syngas yield quality than dry bamboo. The...
- Full Text:
- Authors: Manala, Cecil Khosi
- Date: 2017
- Subjects: Waste products as fuel , Refuse and refuse disposal , Biomass energy , Decomposition (Chemistry)
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/280125 , uj:30095
- Description: M.Ing. (Mechanical Engineering) , Abstract: Energy in its different forms is an important asset to man‟s day-to-day activities from general house hold applications such as cooking and heating to large scale industrial applications such as power generation. However, the current reliance on fossil fuel based energy has become a central concern with respect to sustainable development. Fossil fuels are associated with greenhouse gas emissions and global warming which have been attributed to the dramatic weather and climate change patterns on the planet today posing significant threat to life e. There is, therefore, a need to find more sustainable sources of energy for the planet. Biomass based energy has been used by humanity as a primary source of energy long before the episode of fossil fuel usage. Harnessing of this form of energy has become of overwhelming interest largely due to global warming. It has also been realized that producing renewable energy locally can offer a viable alternative, and facilitate socio-economic development in communities as evidenced by several sustainable energy production projects around South Africa. Biomass contributes 14% of the World‟s primary energy supply. About 75% of its usage is in developing countries. In this work, the organic fraction of municipal solid waste (OFMSW) was quantified at a landfill site in Johannesburg. This was part of a wider project to produce biogas from municipal waste. The potential of that waste to produce syngas by thermal decompositions needs to be investigated as an alternative to anaerobic bio digestion. Furthermore, a bamboo species known as bambusa lacooa, which is currently being introduced for mine dumps rehabilitation in South Africa, was identified as a potential syngas production feedstock. If bamboo based mine dump rehabilitation succeeds, the economic value of the then widely available bamboo needs to be investigated. Production of syngas by pyrolysis becomes one such economic value chain. The aim of this work was therefore to investigate the optimum production of syngas from OFMSW and bamboo by pyrolysis. Specimens of these materials were prepared for thermal decomposition. Bamboo was categorised into wet and dry bamboo and dried in the sun for a period of 14 days. OFMSW made up of mixed food waste was collected from the waste dump landfill site and dried in the sun for a period of 24 hours. The candidate bio-waste materials were subjected to thermal decomposition in a specially designed pyrolysis reactor. Fumes produced during the thermal decomposition were collected at 100˚C temperature intervals from 0 ˚C to 700 ˚C. Dry bamboo produced the highest yield quality of syngas (24% - 23% quality) between 200 ˚C and 400 ˚C. Wet bamboo produced lower syngas yield quality than dry bamboo. The...
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Torrefaction of landfill food waste and characterization of the torrefied biomass
- Authors: Pahla, Godwell
- Date: 2016
- Subjects: Waste products as fuel , Renewable energy sources - Environmental aspects , Biomass energy , Renewable energy sources
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/243012 , uj:25081
- Description: M.Tech. (Chemical Engineering) , Abstract: Greenhouse gas emissions and municipal solid waste management have presented challenges globally. This study aims to help mitigate these challenges by producing renewable energy from landfill food waste. Food waste is carbon neutral since plants use carbon dioxide for growth, so its application in coal-fired boilers will reduce the amount of carbon dioxide emissions thereby mitigating greenhouse effects. The problem with food waste is that it has high moisture content and it is heterogeneous. This limits its heating value and increases energy requirements for grinding. This study investigated the possibility of upgrading the fuel properties of food waste to produce biochar with similar properties to bituminous coal. The food waste was treated by torrefaction. The main aim was to optimize torrefaction conditions and analyze thermal evolution of the sample during torrefaction. The food waste samples were collected from Marie Louis landfill site in Soweto. The samples were dried and milled for particle size reduction. The samples were further analyzed by proximate and ultimate analyses to determine its fuel properties and elemental composition before torrefaction. A tube furnace was used for the torrefaction process. Temperature was varied from 200 – 300 oC at a constant residence time of 40 min and 10 oC/min heating rate. Calorific value, mass yield, energy yield and energy density were computed and used to determine the appropriate torrefaction temperature. Residence time was then varied from 20 – 60 min at a constant torrefaction temperature of 275 oC and 10 oC/min heating rate. Heating rate was then varied keeping residence time at 20min and torrefaction temperature at 275 oC. Torrefaction temperature had a more pronounced effect than residence time and heating rate. The calorific value was upgraded from 19.76 MJ/kg for dried raw food waste to 26.15 MJ/kg for torrefied food waste at the optimum conditions which were 275 oC, 20 min and 10 oC/min. The higher heating value was comparable to that of bituminous coal currently being used for power generation in South Africa. Elemental analysis of biochar showed an increase in carbon content with temperature due to loss of oxygen containing volatiles. It was also observed that biochar obtained at the optimum conditions could easily be pelletized since it assumed the shape of the crucible...
- Full Text:
- Authors: Pahla, Godwell
- Date: 2016
- Subjects: Waste products as fuel , Renewable energy sources - Environmental aspects , Biomass energy , Renewable energy sources
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/243012 , uj:25081
- Description: M.Tech. (Chemical Engineering) , Abstract: Greenhouse gas emissions and municipal solid waste management have presented challenges globally. This study aims to help mitigate these challenges by producing renewable energy from landfill food waste. Food waste is carbon neutral since plants use carbon dioxide for growth, so its application in coal-fired boilers will reduce the amount of carbon dioxide emissions thereby mitigating greenhouse effects. The problem with food waste is that it has high moisture content and it is heterogeneous. This limits its heating value and increases energy requirements for grinding. This study investigated the possibility of upgrading the fuel properties of food waste to produce biochar with similar properties to bituminous coal. The food waste was treated by torrefaction. The main aim was to optimize torrefaction conditions and analyze thermal evolution of the sample during torrefaction. The food waste samples were collected from Marie Louis landfill site in Soweto. The samples were dried and milled for particle size reduction. The samples were further analyzed by proximate and ultimate analyses to determine its fuel properties and elemental composition before torrefaction. A tube furnace was used for the torrefaction process. Temperature was varied from 200 – 300 oC at a constant residence time of 40 min and 10 oC/min heating rate. Calorific value, mass yield, energy yield and energy density were computed and used to determine the appropriate torrefaction temperature. Residence time was then varied from 20 – 60 min at a constant torrefaction temperature of 275 oC and 10 oC/min heating rate. Heating rate was then varied keeping residence time at 20min and torrefaction temperature at 275 oC. Torrefaction temperature had a more pronounced effect than residence time and heating rate. The calorific value was upgraded from 19.76 MJ/kg for dried raw food waste to 26.15 MJ/kg for torrefied food waste at the optimum conditions which were 275 oC, 20 min and 10 oC/min. The higher heating value was comparable to that of bituminous coal currently being used for power generation in South Africa. Elemental analysis of biochar showed an increase in carbon content with temperature due to loss of oxygen containing volatiles. It was also observed that biochar obtained at the optimum conditions could easily be pelletized since it assumed the shape of the crucible...
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Process parameters and conditions for batch production of eco-fuel briquettes
- Authors: Pilusa, Tsietsi Jefrey
- Date: 2012-09-04
- Subjects: Fuel - Combustion , Fuel , Waste products as fuel
- Type: Thesis
- Identifier: uj:3505 , http://hdl.handle.net/10210/6894
- Description: M.Tech. , In this work, eco-fuel briquettes made from a mixture of 32% spent coffee grounds, 23% coal fines, 11% saw dust, 18% mielie husks, 10% waste paper and 6% paper pulp contaminated water, respectively were investigated. Various processing stages such as briquetting, drying, combustion and flue gas emissions were investigated in order to evaluate the socio-economic viability of the batch production of eco-fuel briquettes from biomass waste material. Each stage was studied independently in order to develop basic models that contained material and energy balances. A screw press briquetting machine was designed and fabricated as part of this work to be tested against the legacy foundation Porta press, and the Bikernmayer hand brick press. The compaction of the biomass waste material into briquettes follows the principle of physical interlocking of the fine particles within the plant fibres, natural material binding due to released cellulose content, as well as reduction in porosity, due to a simultaneous dewatering and compaction action. The processing variables such as cycle times and pressure were studied. The Bikernmayer press is preferred as it produced briquettes of higher bulk densities and lower moisture content as compared to the other presses. The drying was investigated in a laboratory scale convective dryer to establish typical convection parameters. A drying system that utilizes produced briquettes as a heating medium is proposed, and here drying will be effected over a refractory brick fireplace by means of convection and radiation. A basic model was set up to include radiation with the convection to predict a drying time of 4.8 hours. The combustion of briquettes was investigated using a POCA ceramic stove linked to the testo Portable Emission Analyzer System. This enabled an air-to-fuel ratio of 1.44 and a burning rate of 2g per minute to be established. The energy transfer efficiency for boiling a pot of water was found to be 85%. The gas emissions were found to be within the acceptable limits, as set out by OSHA. A standard initial economic evaluation was performed based on a briquette selling price of R2.26 per kilogram for the ease of accommodating the local market. The financial model for both Porta press and screw press were not economically viable, as their running costs were greater than the gross project revenues. For the Bikernmayer conceptual model, with a total capital investment of R669, 981+ VAT (this includes one year operating cost) and a project life of five years, the gross Process parameters and conditions batch production of eco-fuel briquettes profit margin is 44%, the profitability index is 5.33 and the internal Rate of return 31.44%. The net present value and return period are R676, 896 and 0.408 years respectively. The customer profile as currently at hand is 17% of the selected area within 80 m radius from production site. The remaining 83% will be in need of energy as they become aware of the new product offering. The selling of the briquettes should be accompanied by an education process, to avoid the dangers of heating indoors. The principal driver for this project is socio economic development and it is being strengthened by Eskom’s inability to provide sufficient energy. A secondary driver is the global drive to reduce emissions and fossil fuel usage; this technology does exactly this whilst diverting waste from landfill. In the Polokwane declaration (2008), it is stated that South Africa will have no calorific waste to landfill by 2014. Hence legislation will also provide a major part of the drive.
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- Authors: Pilusa, Tsietsi Jefrey
- Date: 2012-09-04
- Subjects: Fuel - Combustion , Fuel , Waste products as fuel
- Type: Thesis
- Identifier: uj:3505 , http://hdl.handle.net/10210/6894
- Description: M.Tech. , In this work, eco-fuel briquettes made from a mixture of 32% spent coffee grounds, 23% coal fines, 11% saw dust, 18% mielie husks, 10% waste paper and 6% paper pulp contaminated water, respectively were investigated. Various processing stages such as briquetting, drying, combustion and flue gas emissions were investigated in order to evaluate the socio-economic viability of the batch production of eco-fuel briquettes from biomass waste material. Each stage was studied independently in order to develop basic models that contained material and energy balances. A screw press briquetting machine was designed and fabricated as part of this work to be tested against the legacy foundation Porta press, and the Bikernmayer hand brick press. The compaction of the biomass waste material into briquettes follows the principle of physical interlocking of the fine particles within the plant fibres, natural material binding due to released cellulose content, as well as reduction in porosity, due to a simultaneous dewatering and compaction action. The processing variables such as cycle times and pressure were studied. The Bikernmayer press is preferred as it produced briquettes of higher bulk densities and lower moisture content as compared to the other presses. The drying was investigated in a laboratory scale convective dryer to establish typical convection parameters. A drying system that utilizes produced briquettes as a heating medium is proposed, and here drying will be effected over a refractory brick fireplace by means of convection and radiation. A basic model was set up to include radiation with the convection to predict a drying time of 4.8 hours. The combustion of briquettes was investigated using a POCA ceramic stove linked to the testo Portable Emission Analyzer System. This enabled an air-to-fuel ratio of 1.44 and a burning rate of 2g per minute to be established. The energy transfer efficiency for boiling a pot of water was found to be 85%. The gas emissions were found to be within the acceptable limits, as set out by OSHA. A standard initial economic evaluation was performed based on a briquette selling price of R2.26 per kilogram for the ease of accommodating the local market. The financial model for both Porta press and screw press were not economically viable, as their running costs were greater than the gross project revenues. For the Bikernmayer conceptual model, with a total capital investment of R669, 981+ VAT (this includes one year operating cost) and a project life of five years, the gross Process parameters and conditions batch production of eco-fuel briquettes profit margin is 44%, the profitability index is 5.33 and the internal Rate of return 31.44%. The net present value and return period are R676, 896 and 0.408 years respectively. The customer profile as currently at hand is 17% of the selected area within 80 m radius from production site. The remaining 83% will be in need of energy as they become aware of the new product offering. The selling of the briquettes should be accompanied by an education process, to avoid the dangers of heating indoors. The principal driver for this project is socio economic development and it is being strengthened by Eskom’s inability to provide sufficient energy. A secondary driver is the global drive to reduce emissions and fossil fuel usage; this technology does exactly this whilst diverting waste from landfill. In the Polokwane declaration (2008), it is stated that South Africa will have no calorific waste to landfill by 2014. Hence legislation will also provide a major part of the drive.
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