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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A multiple scenario analysis into the potential for bioethanol production from maize in South Africa
- Authors: Smith, Maria
- Date: 2010-05-27T06:06:58Z
- Subjects: Agriculture and energy , Agricultural wastes as fuel , Biomass energy , Alcohol as fuel
- Type: Thesis
- Identifier: uj:6849 , http://hdl.handle.net/10210/3280
- Description: M.Sc. , Biofuels have the potential to reduce a country’s dependence on imported oil, to ensure diversity of energy sources, to increase the availability of renewable energy sources and to address global environmental issues. In recognition of the potential benefits of the production and use of biofuels, the Department of Minerals and Energy released the Draft Biofuels Industrial Strategy in December 2006 with the aim to increase the use of biofuels in South Africa to replace 4.5% of conventional transport fuels by 2013. However, there are several barriers that need to be overcome before South Africa can establish a large-scale biofuel industry to achieve the DME’s biofuel target. This includes environmental barriers, such as the availability of land for the cultivation of biofuel feedstocks and potential threats to food security. This study focuses on these environmental barriers and aims to determine the potential for bioethanol production from maize in South Africa to 2013. To this purpose, a bioethanol potential model is developed to simulate the potential for bioethanol production from maize in South Africa between 2008 and 2013. The model incorporates four key elements that all impact on the availability of maize for bioethanol production, namely: maize demand; maize supply; the demand for maize as biomaterial; and the available land area for the cultivation of maize. The study makes further use of the scenario planning method to determine the potential for bioethanol production from maize in South Africa. Four unique bioethanol potential scenarios are designed and simulated within the bioethanol potential model developed for this purpose. Each scenario plays out a differentstoryline for the future social, economic and natural environment that will impact on the availability of maize for bioethanol production. The results of the bioethanol potential scenario simulations show that South Africa will be able to produce enough maize to meet the DME’s biofuel target of 1.2 billion liters of bioethanol for all scenarios between 2009 and 2010. From 2011 onwards, the bioethanol potential decreases below the DME’s target value in both the worst case and rapid change scenarios. The study concludes that the production of bioethanol from maize in South Africa will have various social, economic and environmental consequences for the country’s agricultural sector. The depletion of domestic maize supplies will seriously threaten food security and consequently, increase the country’s dependence on maize imports. This will not only affect the country’s maize producing regions, but spread throughout South Africa as the demand for agriculturally productive land for maize production increases. Domestic food security is therefore at risk and South Africa will have to resort to other energy technologies to achieve a sustainable and renewable energy future for road transport.
- Full Text:
A multiple scenario analysis into the potential for bioethanol production from maize in South Africa
- Authors: Smith, Maria
- Date: 2010-05-27T06:06:58Z
- Subjects: Agriculture and energy , Agricultural wastes as fuel , Biomass energy , Alcohol as fuel
- Type: Thesis
- Identifier: uj:6849 , http://hdl.handle.net/10210/3280
- Description: M.Sc. , Biofuels have the potential to reduce a country’s dependence on imported oil, to ensure diversity of energy sources, to increase the availability of renewable energy sources and to address global environmental issues. In recognition of the potential benefits of the production and use of biofuels, the Department of Minerals and Energy released the Draft Biofuels Industrial Strategy in December 2006 with the aim to increase the use of biofuels in South Africa to replace 4.5% of conventional transport fuels by 2013. However, there are several barriers that need to be overcome before South Africa can establish a large-scale biofuel industry to achieve the DME’s biofuel target. This includes environmental barriers, such as the availability of land for the cultivation of biofuel feedstocks and potential threats to food security. This study focuses on these environmental barriers and aims to determine the potential for bioethanol production from maize in South Africa to 2013. To this purpose, a bioethanol potential model is developed to simulate the potential for bioethanol production from maize in South Africa between 2008 and 2013. The model incorporates four key elements that all impact on the availability of maize for bioethanol production, namely: maize demand; maize supply; the demand for maize as biomaterial; and the available land area for the cultivation of maize. The study makes further use of the scenario planning method to determine the potential for bioethanol production from maize in South Africa. Four unique bioethanol potential scenarios are designed and simulated within the bioethanol potential model developed for this purpose. Each scenario plays out a differentstoryline for the future social, economic and natural environment that will impact on the availability of maize for bioethanol production. The results of the bioethanol potential scenario simulations show that South Africa will be able to produce enough maize to meet the DME’s biofuel target of 1.2 billion liters of bioethanol for all scenarios between 2009 and 2010. From 2011 onwards, the bioethanol potential decreases below the DME’s target value in both the worst case and rapid change scenarios. The study concludes that the production of bioethanol from maize in South Africa will have various social, economic and environmental consequences for the country’s agricultural sector. The depletion of domestic maize supplies will seriously threaten food security and consequently, increase the country’s dependence on maize imports. This will not only affect the country’s maize producing regions, but spread throughout South Africa as the demand for agriculturally productive land for maize production increases. Domestic food security is therefore at risk and South Africa will have to resort to other energy technologies to achieve a sustainable and renewable energy future for road transport.
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Study on regulations, policies and permits for implementation of bioenergy systems
- Chingono, Talent, Mbohwa, Charles
- Authors: Chingono, Talent , Mbohwa, Charles
- Date: 2016
- Subjects: Bioenergy systems , Biomass energy
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/218462 , uj:21774 , Citation: Chingono, T & Mbohwa, C. 2016. Study on regulations, policies and permits for implementation of bioenergy systems. Proceedings of the 2016 International Conference on Industrial Engineering and Operations Management, 23-25 September 2016.
- Description: Abstract: The popularity of the Organic Fuel comes mostly from its Economic and Environmental benefits, and it can be effortlessly changed over into vitality for direct warming applications or potentially power era frameworks. Bioenergy can possibly break the Cycles of Poverty by developing energy security, food security, work creation, wage diversification and rural advancement. Care is required in light of the fact that bioenergy could have both positive and negative effects on nearby nourishment security. The significance of building up the Renewable part is further underscored by its consideration as a coordinated vital venture in the National Infrastructure Plan. This is managed by the Presidential Infrastructure Coordinating Committee, and is done for catalyzing development and development in South Africa. Renewable energy is likewise deliberately seen as a road through which the South African Government can react to the test of environmental change, enhance vitality security by broadening wellsprings of vitality supply, and impel green development through localisation and strengthening (DME 2003).Objectives were to take part in a complete audit of the national legitimate structures for bioenergy in South Africa. Controls, approaches and allows fundamentally explored and these will be supplemented by direct meetings with related Stakeholders. Existing Feasibility concentrates on that were completed for bioenergy Development were inspected and heightening elements were utilized to overhaul the expenses to reflect current costs. South Africa's Bioenergy Framework Main occasions were outlined and investigated and summarised. Recommendations were suggested.
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- Authors: Chingono, Talent , Mbohwa, Charles
- Date: 2016
- Subjects: Bioenergy systems , Biomass energy
- Language: English
- Type: Conference proceedings
- Identifier: http://hdl.handle.net/10210/218462 , uj:21774 , Citation: Chingono, T & Mbohwa, C. 2016. Study on regulations, policies and permits for implementation of bioenergy systems. Proceedings of the 2016 International Conference on Industrial Engineering and Operations Management, 23-25 September 2016.
- Description: Abstract: The popularity of the Organic Fuel comes mostly from its Economic and Environmental benefits, and it can be effortlessly changed over into vitality for direct warming applications or potentially power era frameworks. Bioenergy can possibly break the Cycles of Poverty by developing energy security, food security, work creation, wage diversification and rural advancement. Care is required in light of the fact that bioenergy could have both positive and negative effects on nearby nourishment security. The significance of building up the Renewable part is further underscored by its consideration as a coordinated vital venture in the National Infrastructure Plan. This is managed by the Presidential Infrastructure Coordinating Committee, and is done for catalyzing development and development in South Africa. Renewable energy is likewise deliberately seen as a road through which the South African Government can react to the test of environmental change, enhance vitality security by broadening wellsprings of vitality supply, and impel green development through localisation and strengthening (DME 2003).Objectives were to take part in a complete audit of the national legitimate structures for bioenergy in South Africa. Controls, approaches and allows fundamentally explored and these will be supplemented by direct meetings with related Stakeholders. Existing Feasibility concentrates on that were completed for bioenergy Development were inspected and heightening elements were utilized to overhaul the expenses to reflect current costs. South Africa's Bioenergy Framework Main occasions were outlined and investigated and summarised. Recommendations were suggested.
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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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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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Enhancing biogas production from lawn grass by optimizing selected factors involved in anaerobic digestion
- Authors: Sibiya, Noxolo Thandeka
- Date: 2016
- Subjects: Biomass energy , Renewable energy resources , Refuse and refuse disposal - Biodegradation
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/225327 , uj:22755
- Description: M.Tech. (Chemical Engineering) , Abstract: Biogas technology via anaerobic digestion (AD) is considered as an alternative option to reduce the emission of greenhouse gases, improve energy efficiency and address increasing dependency on imported fossil fuel. Although biogas can be produced easily, numerous researches have shown that the efficiency of methane production, especially from grass, is not optimal due to some factors affecting the AD rocess directly and indirectly. Therefore, this master’s dissertation focuses on evaluating the techniques that can be used to enhance the biodegradability of lawn grass, and subsequently improves biogas and methane production under anaerobic condition. The effects of operational parameters such as temperature, pH, loading rate, and retention time were evaluated. Techniques including recirculation of digestate, alkaline (NaOH) pre-treatment and co-digestion were also investigated. The characteristics of the substrate were determined in order to verify the suitability of the substrate for AD process. Biogas production from lawn grass was studied in the batch laboratory scale digester (1000 mL) with the working volume of 800 mL. Automatic Methane Potential Test System (AMPTS II) was used to measure bio-methane potential and methane content was measured using gas chromatography (GC, claurus 580). Although all the techniques have proven to enhance biogas and methane production from lawn grass, co-digestion has been considered as the most preferable method for enhanced biogas and methane production. The highest biogas yield was obtained when grass was co-digested with cow dung, while the maximum methane was observed when pig manure was a co-substrate with grass at the ratio of 1:1 (25:25 g). The suitable environmental condition for AD on this study was found to be at 45 ºC and pH of 6.5, while the optimal retention time was found to be 8 days, regardless of the effect of temperature and pH. An increase of biogas and methane production by 10% was observed when the digester loading rate was increased from 20 g/L to 60 g/L, whereas higher methane content was obtained in a digester with 30 % recycled solid digestate. It was also found that pre-treating lawn grass with 0.093 M NaOH at 40 and 55 ºC prior the AD process resulted in a significant increase in bio-methane potential from 813 to 1204 NmL and methane content from 40 to 52 %.
- Full Text:
- Authors: Sibiya, Noxolo Thandeka
- Date: 2016
- Subjects: Biomass energy , Renewable energy resources , Refuse and refuse disposal - Biodegradation
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/225327 , uj:22755
- Description: M.Tech. (Chemical Engineering) , Abstract: Biogas technology via anaerobic digestion (AD) is considered as an alternative option to reduce the emission of greenhouse gases, improve energy efficiency and address increasing dependency on imported fossil fuel. Although biogas can be produced easily, numerous researches have shown that the efficiency of methane production, especially from grass, is not optimal due to some factors affecting the AD rocess directly and indirectly. Therefore, this master’s dissertation focuses on evaluating the techniques that can be used to enhance the biodegradability of lawn grass, and subsequently improves biogas and methane production under anaerobic condition. The effects of operational parameters such as temperature, pH, loading rate, and retention time were evaluated. Techniques including recirculation of digestate, alkaline (NaOH) pre-treatment and co-digestion were also investigated. The characteristics of the substrate were determined in order to verify the suitability of the substrate for AD process. Biogas production from lawn grass was studied in the batch laboratory scale digester (1000 mL) with the working volume of 800 mL. Automatic Methane Potential Test System (AMPTS II) was used to measure bio-methane potential and methane content was measured using gas chromatography (GC, claurus 580). Although all the techniques have proven to enhance biogas and methane production from lawn grass, co-digestion has been considered as the most preferable method for enhanced biogas and methane production. The highest biogas yield was obtained when grass was co-digested with cow dung, while the maximum methane was observed when pig manure was a co-substrate with grass at the ratio of 1:1 (25:25 g). The suitable environmental condition for AD on this study was found to be at 45 ºC and pH of 6.5, while the optimal retention time was found to be 8 days, regardless of the effect of temperature and pH. An increase of biogas and methane production by 10% was observed when the digester loading rate was increased from 20 g/L to 60 g/L, whereas higher methane content was obtained in a digester with 30 % recycled solid digestate. It was also found that pre-treating lawn grass with 0.093 M NaOH at 40 and 55 ºC prior the AD process resulted in a significant increase in bio-methane potential from 813 to 1204 NmL and methane content from 40 to 52 %.
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Optimization of biogas production from City of Johannesburg market waste by anaerobic digestion for sustainable energy development
- Authors: Singh, Suraya
- Date: 2018
- Subjects: Biogas , Biomass energy
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/295034 , uj:32113
- Description: M.Tech. (Chemical Engineering) , Abstract: Biogas, as a renewable energy source, is regarded as a viable alternative to the burning of fossil fuels to meet energy demands. The production of biogas to meet energy needs not only has environmental benefits such as reduction in greenhouse gas emissions and responsible waste disposal but also socio-economic benefits, especially when applied to a rural setting, such as improvements in employment, professional qualification and overall food supply of the local population. The main objective of this study was to determine optimum biogas production from City of Johannesburg (CoJ) market waste, composed primarily of fruit and vegetable waste (FVW), under anaerobic condition. The influence of operational factors such as temperature, pH, loading rate and retention time were evaluated. The co-digestion of FVW with cow dung (CD) at varying mixing ratios was also evaluated as a technique to optimize biogas production. Mono-digestion of FVW at thermophilic temperatures were optimum for both biogas and methane production. Changes in organic loading rate (OLR) indicated that with increases in OLR there were increases in both biogas and methane production. The highest biogas and methane production occurred for an OLR of FVW: 200g. The optimum retention time for biogas and methane production was determined to be 14 days and 10 days respectively. The explanation for the prolonged biogas and methane production has been accredited to the fact that there was a greater component of biodegradable material available for breakdown by methanogenic bacteria but even more critical than that was the alkaline pH of 7.18 of this substrate mixture at the commencement of digestion. However, experimental results indicated that co-digestion is the preferred method to optimize biogas and methane production. According to the experimental results obtained, a mixing ratio of FVW: CD of 20:40g is the optimum substrate mixture for both biogas and methane production. The optimum environmental conditions for co-digestion was found to be at 37°C with a pH range between 7.12 to 7.18, while the optimal retention time was found to be 33 days. It was found that when the mixing ratios contained between 50% and less cow dung with corresponding increases in FVW, there were drastic reductions in the digester stability and overall production rates for those substrate mixing ratios. It was therefore concluded that in order to ensure sustained and good biogas and methane production via co-digestion, the CD content should remain above 50% of the total mixture.
- Full Text:
- Authors: Singh, Suraya
- Date: 2018
- Subjects: Biogas , Biomass energy
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/295034 , uj:32113
- Description: M.Tech. (Chemical Engineering) , Abstract: Biogas, as a renewable energy source, is regarded as a viable alternative to the burning of fossil fuels to meet energy demands. The production of biogas to meet energy needs not only has environmental benefits such as reduction in greenhouse gas emissions and responsible waste disposal but also socio-economic benefits, especially when applied to a rural setting, such as improvements in employment, professional qualification and overall food supply of the local population. The main objective of this study was to determine optimum biogas production from City of Johannesburg (CoJ) market waste, composed primarily of fruit and vegetable waste (FVW), under anaerobic condition. The influence of operational factors such as temperature, pH, loading rate and retention time were evaluated. The co-digestion of FVW with cow dung (CD) at varying mixing ratios was also evaluated as a technique to optimize biogas production. Mono-digestion of FVW at thermophilic temperatures were optimum for both biogas and methane production. Changes in organic loading rate (OLR) indicated that with increases in OLR there were increases in both biogas and methane production. The highest biogas and methane production occurred for an OLR of FVW: 200g. The optimum retention time for biogas and methane production was determined to be 14 days and 10 days respectively. The explanation for the prolonged biogas and methane production has been accredited to the fact that there was a greater component of biodegradable material available for breakdown by methanogenic bacteria but even more critical than that was the alkaline pH of 7.18 of this substrate mixture at the commencement of digestion. However, experimental results indicated that co-digestion is the preferred method to optimize biogas and methane production. According to the experimental results obtained, a mixing ratio of FVW: CD of 20:40g is the optimum substrate mixture for both biogas and methane production. The optimum environmental conditions for co-digestion was found to be at 37°C with a pH range between 7.12 to 7.18, while the optimal retention time was found to be 33 days. It was found that when the mixing ratios contained between 50% and less cow dung with corresponding increases in FVW, there were drastic reductions in the digester stability and overall production rates for those substrate mixing ratios. It was therefore concluded that in order to ensure sustained and good biogas and methane production via co-digestion, the CD content should remain above 50% of the total mixture.
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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)
- Full Text:
- 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)
- Full Text:
Effect of nutrient addition during anaerobic digestion of potato peels and maize husk
- Ramatsa, Ishmael, Sibiya, Noxolo, Huberts, Roberth
- Authors: Ramatsa, Ishmael , Sibiya, Noxolo , Huberts, Roberth
- Date: 2014
- Subjects: Anaerobic bacteria , Renewable energy sources , Biomass energy , Biogas
- Type: Article
- Identifier: uj:5091 , http://hdl.handle.net/10210/13681
- Description: The composition of the substrate and nutrients addition plays a very significant role during the production of the biogas. For this reason this paper tries to evaluate the effect of nutrients addition during biogas production under anaerobic conditions. Potato peels wastes and maize husk were anaerobically digested in a 5 liter scale reactor at mesophilic conditions (32 o C). The characteristics of the potato peels were and maize husk are presented in Table 1. The results obtained indicated that the addition of the nutrients during anaerobic digestion has an influence on the biogas production, meanwhile methane content in biogas varied from 48 to 64%.
- Full Text:
- Authors: Ramatsa, Ishmael , Sibiya, Noxolo , Huberts, Roberth
- Date: 2014
- Subjects: Anaerobic bacteria , Renewable energy sources , Biomass energy , Biogas
- Type: Article
- Identifier: uj:5091 , http://hdl.handle.net/10210/13681
- Description: The composition of the substrate and nutrients addition plays a very significant role during the production of the biogas. For this reason this paper tries to evaluate the effect of nutrients addition during biogas production under anaerobic conditions. Potato peels wastes and maize husk were anaerobically digested in a 5 liter scale reactor at mesophilic conditions (32 o C). The characteristics of the potato peels were and maize husk are presented in Table 1. The results obtained indicated that the addition of the nutrients during anaerobic digestion has an influence on the biogas production, meanwhile methane content in biogas varied from 48 to 64%.
- Full Text:
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...
- Full Text:
Polarimetric synthetic aperture radar (POLSAR) above ground biomass estimation in communal African savanna woodlands
- Authors: Paradzayi, Charles
- Date: 2012
- Subjects: Polarimetric synthetic aperture radar , Biomass energy , Polarimetric remote sensing , Radar in earth sciences , Energy crops , Fuelwood , Charcoal , Savannas
- Type: Thesis (D. Phil.)
- Identifier: uj:9530 , http://hdl.handle.net/10210/5958
- Description: D. Phil. (Energy Studies) , Woody biomass resource, mostly in the form of fuelwood and charcoal, is the predominant source of basic domestic energy for low-income rural and urban households in sub-Saharan Africa. In most developing economies, quantitative information on available woody biomass resources, at scales appropriate for energy planning purposes is often lacking. The continued reliance on biomass resources to meet the sustenance and livelihood needs in poor economies is exerting unsustainable pressure on the resources. The VW Foundation initiated a multi-institutional and inter-disciplinary bioenergy modelling project that sought to provide stakeholders with quantitative information on available woody biomass and its sustainable utilisation in rural communal woodlands in three countries in southern Africa. The overall project themes related to: (i) remote sensing approaches for quantifying woody biomass (ii) modelling rural energy at the village level (iii) biomass conversion technological pathways (iv) environmental and socio-economic analysis of fuelwood consumption (v) spatial-temporal analysis of the communal woodland dynamics. The exploitation of traditional biomass resources, for cash and mercantile purposes, is leading to accelerated losses of carbon sinks, natural forests and biodiversity, as well as creating local scarcity of woody biomass. Although communal woodlands are important sinks for carbon sequestration, for which developed countries are willing to pay, many poor communities are often caught between conserving communal woodlands and meeting their immediate domestic energy needs. Carbon stocks in communal woodlands are becoming crucial input for the reporting requirements of international conventions such as Reducing Emissions from Degradation and forest Deforestation (REDD) and the Kyoto Protocol on Climate Change (KPCC). This research investigated the capability of using full polarimetric spaceborne ALOS PALSAR retrievals for mapping and quantifying above ground woody biomass in semi-open savanna woodlands in South Africa, Mozambique and Zambia. Existing allometric equations were used to estimate above ground biomass densities from tree parameter measurements in selected training plots. The optimum polarisation channels for estimating standing woody biomass in savanna woodlands were ascertained by investigating the correlation between above ground biomass densities and normalised backscattering coefficient ( σ o ) from retrievals acquired using the horizontal transmit and horizontal receive (HH), horizontal transmit and vertical receive (HV), and vertical transmit and vertical receive (VV) polarisation states, under both wet and dry conditions. The training datasets were bootstrapped since the number of the training plots was limited. Regression and prediction equations have been established between the above ground biomass densities and backscatter intensities for the resampled training dataset, with the highest correlation coefficient for each polarisation. The method developed in this work identifies woody vegetation from the interaction of full polarimetric radar signals with terrain scattering mechanisms and maps the distribution of woody vegetation at any required scale. Terrain scattering mechanisms were classified by (i) performing an unsupervised entropy/alpha (H/α) Wishart classification procedure on ALOS PALSAR full beam imagery, based on the Cloude-Pottier decomposition, and (ii) using scattering classes from the unsupervised classification as training input for the maximum likelihood classification procedure on Freeman decomposition data. The classification results were used to delineate woody and non-woody vegetation classes. Equations to predict above ground biomass densities were developed by inverting the regression equations, which were established from the relationship between backscatter intensities and above ground biomass densities from selected training plots. The predicted biomass densities were reclassified into five categories and the mean biomass density values for the categories were used to compute the available woody biomass resources at the desired scale. The woody vegetation classes were used to mask biomass densities estimated from prediction equations. The research has contributed to an improved understanding of the interpretation and analysis of full polarimetric spaceborne retrievals acquired over African semi-open savanna woodlands by extending approaches developed previously for boreal and temperate region forests. The research work has succeeded to map and to some extent, quantify above ground woody biomass at landscape scale, using full polarimetry spaceborne ALOS PALSAR retrievals validated against plot-scale measurements. The results contribute to the estimation of woody biomass resources for national and global energy and carbon sequestration initiatives. However, the training dataset was limited; hence, the resultant biomass estimation equations are site specific. The approach developed in this work needs refinement before it can be utilised for operational monitoring of savanna woodlands and extrapolation of landscape scale biomass. Estimating woody biomass from the polarimetric retrievals is an improvement on techniques based on optical remote sensing methods because the response of the radar signal is responsive to the physical parameters being surveyed (mass/volume of woody biomass) rather than a surrogate (top of canopy greenness). The purpose of the VW Foundation Bioenergy Modelling project was to estimate available and accessible biomass within village precincts. Results from this work were used to develop GIS-based spatial models for estimating fuelwood collection times and the associated 'least-cost' collection routes between households and selected woodlands. The models took into account the constraints imposed by land tenure systems and geophysical factors such as terrain and watercourses to compute the time spend on fuelwood collection. The fuelwood collection effort is used to estimate the balance between rates of exploitation and woodland regeneration in order to determine the point at which harvesting fuelwood becomes unsustainable. An important output from the GIS models is a woodlands at risk map, which ranks the vulnerability of woody biomass resources in terms of travel times from surrounding villages.
- Full Text:
- Authors: Paradzayi, Charles
- Date: 2012
- Subjects: Polarimetric synthetic aperture radar , Biomass energy , Polarimetric remote sensing , Radar in earth sciences , Energy crops , Fuelwood , Charcoal , Savannas
- Type: Thesis (D. Phil.)
- Identifier: uj:9530 , http://hdl.handle.net/10210/5958
- Description: D. Phil. (Energy Studies) , Woody biomass resource, mostly in the form of fuelwood and charcoal, is the predominant source of basic domestic energy for low-income rural and urban households in sub-Saharan Africa. In most developing economies, quantitative information on available woody biomass resources, at scales appropriate for energy planning purposes is often lacking. The continued reliance on biomass resources to meet the sustenance and livelihood needs in poor economies is exerting unsustainable pressure on the resources. The VW Foundation initiated a multi-institutional and inter-disciplinary bioenergy modelling project that sought to provide stakeholders with quantitative information on available woody biomass and its sustainable utilisation in rural communal woodlands in three countries in southern Africa. The overall project themes related to: (i) remote sensing approaches for quantifying woody biomass (ii) modelling rural energy at the village level (iii) biomass conversion technological pathways (iv) environmental and socio-economic analysis of fuelwood consumption (v) spatial-temporal analysis of the communal woodland dynamics. The exploitation of traditional biomass resources, for cash and mercantile purposes, is leading to accelerated losses of carbon sinks, natural forests and biodiversity, as well as creating local scarcity of woody biomass. Although communal woodlands are important sinks for carbon sequestration, for which developed countries are willing to pay, many poor communities are often caught between conserving communal woodlands and meeting their immediate domestic energy needs. Carbon stocks in communal woodlands are becoming crucial input for the reporting requirements of international conventions such as Reducing Emissions from Degradation and forest Deforestation (REDD) and the Kyoto Protocol on Climate Change (KPCC). This research investigated the capability of using full polarimetric spaceborne ALOS PALSAR retrievals for mapping and quantifying above ground woody biomass in semi-open savanna woodlands in South Africa, Mozambique and Zambia. Existing allometric equations were used to estimate above ground biomass densities from tree parameter measurements in selected training plots. The optimum polarisation channels for estimating standing woody biomass in savanna woodlands were ascertained by investigating the correlation between above ground biomass densities and normalised backscattering coefficient ( σ o ) from retrievals acquired using the horizontal transmit and horizontal receive (HH), horizontal transmit and vertical receive (HV), and vertical transmit and vertical receive (VV) polarisation states, under both wet and dry conditions. The training datasets were bootstrapped since the number of the training plots was limited. Regression and prediction equations have been established between the above ground biomass densities and backscatter intensities for the resampled training dataset, with the highest correlation coefficient for each polarisation. The method developed in this work identifies woody vegetation from the interaction of full polarimetric radar signals with terrain scattering mechanisms and maps the distribution of woody vegetation at any required scale. Terrain scattering mechanisms were classified by (i) performing an unsupervised entropy/alpha (H/α) Wishart classification procedure on ALOS PALSAR full beam imagery, based on the Cloude-Pottier decomposition, and (ii) using scattering classes from the unsupervised classification as training input for the maximum likelihood classification procedure on Freeman decomposition data. The classification results were used to delineate woody and non-woody vegetation classes. Equations to predict above ground biomass densities were developed by inverting the regression equations, which were established from the relationship between backscatter intensities and above ground biomass densities from selected training plots. The predicted biomass densities were reclassified into five categories and the mean biomass density values for the categories were used to compute the available woody biomass resources at the desired scale. The woody vegetation classes were used to mask biomass densities estimated from prediction equations. The research has contributed to an improved understanding of the interpretation and analysis of full polarimetric spaceborne retrievals acquired over African semi-open savanna woodlands by extending approaches developed previously for boreal and temperate region forests. The research work has succeeded to map and to some extent, quantify above ground woody biomass at landscape scale, using full polarimetry spaceborne ALOS PALSAR retrievals validated against plot-scale measurements. The results contribute to the estimation of woody biomass resources for national and global energy and carbon sequestration initiatives. However, the training dataset was limited; hence, the resultant biomass estimation equations are site specific. The approach developed in this work needs refinement before it can be utilised for operational monitoring of savanna woodlands and extrapolation of landscape scale biomass. Estimating woody biomass from the polarimetric retrievals is an improvement on techniques based on optical remote sensing methods because the response of the radar signal is responsive to the physical parameters being surveyed (mass/volume of woody biomass) rather than a surrogate (top of canopy greenness). The purpose of the VW Foundation Bioenergy Modelling project was to estimate available and accessible biomass within village precincts. Results from this work were used to develop GIS-based spatial models for estimating fuelwood collection times and the associated 'least-cost' collection routes between households and selected woodlands. The models took into account the constraints imposed by land tenure systems and geophysical factors such as terrain and watercourses to compute the time spend on fuelwood collection. The fuelwood collection effort is used to estimate the balance between rates of exploitation and woodland regeneration in order to determine the point at which harvesting fuelwood becomes unsustainable. An important output from the GIS models is a woodlands at risk map, which ranks the vulnerability of woody biomass resources in terms of travel times from surrounding villages.
- Full Text:
Biogas purification and upgrading for vehicular fuel application
- Authors: Maile, Olivia Ireen
- Date: 2016
- Subjects: Reneable energy sources , Biogas , Biomass energy
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/243015 , uj:25082
- Description: M.Tech. (Chemical Engineering) , Abstract: Energy is used in the form of electricity, heat, and fuel for lighting, cooking, transportation, and manufacturing of different kind of products. South Africa has faced a long-term struggle on energy shortages which may be related to the 20% growth in the country’s electricity consumption and underinvestment on energy. Thus, the need for producing clean energy from alternative renewable and sustainable energy sources remains an attractive technology. Biogas is energy produced by anaerobic digestion of biodegradable organic waste such as garden waste, food waste, municipal waste, industrial waste and sewage sludge. However, it may not be fully exploited because it contains impurities which limit its application. It can be purified and upgraded using techniques such as high-pressure water scrubbing, pressure swing adsorption, membrane separation, activated carbon sieve, cryogenic separation, chemical absorption. This study focuses on chemical absorption as it can yield biogas with over 95 % CH4 by volume. The substrate used to produce biogas in this study was grass inoculated with cow dung. Sodium hydroxide and acetic acid were used to adjust the pH of the feedstock. The chemicals absorbents of focus are sodium hydroxide, potassium hydroxide, ammonia solution and monoethanolamine. Two kinds of setups were used for this study; biochemical methane potential (BMP) assay tests using the Bioprocess Control AMPTS II and a custom made setup using Buchner flasks. Gas Chromatography was used for biogas analysis. The raw biogas contained on average 52% CH4 by volume which improved to over 80% CH4 after CO2 absorption. The CO2 removal efficiency improved from 22% to 66% for the alkalis and was also quite comparable for MEA and NH3 as it increased from 51% to 67%. The removal efficiency for NH3 and MEA increased from 69% to 79% on average with CH4 concentration reaching over 85% volume at 40 °C. The achievable calorific value for this study ranged from 25 to 33.5 MJ/Nm3.
- Full Text:
- Authors: Maile, Olivia Ireen
- Date: 2016
- Subjects: Reneable energy sources , Biogas , Biomass energy
- Language: English
- Type: Masters (Thesis)
- Identifier: http://hdl.handle.net/10210/243015 , uj:25082
- Description: M.Tech. (Chemical Engineering) , Abstract: Energy is used in the form of electricity, heat, and fuel for lighting, cooking, transportation, and manufacturing of different kind of products. South Africa has faced a long-term struggle on energy shortages which may be related to the 20% growth in the country’s electricity consumption and underinvestment on energy. Thus, the need for producing clean energy from alternative renewable and sustainable energy sources remains an attractive technology. Biogas is energy produced by anaerobic digestion of biodegradable organic waste such as garden waste, food waste, municipal waste, industrial waste and sewage sludge. However, it may not be fully exploited because it contains impurities which limit its application. It can be purified and upgraded using techniques such as high-pressure water scrubbing, pressure swing adsorption, membrane separation, activated carbon sieve, cryogenic separation, chemical absorption. This study focuses on chemical absorption as it can yield biogas with over 95 % CH4 by volume. The substrate used to produce biogas in this study was grass inoculated with cow dung. Sodium hydroxide and acetic acid were used to adjust the pH of the feedstock. The chemicals absorbents of focus are sodium hydroxide, potassium hydroxide, ammonia solution and monoethanolamine. Two kinds of setups were used for this study; biochemical methane potential (BMP) assay tests using the Bioprocess Control AMPTS II and a custom made setup using Buchner flasks. Gas Chromatography was used for biogas analysis. The raw biogas contained on average 52% CH4 by volume which improved to over 80% CH4 after CO2 absorption. The CO2 removal efficiency improved from 22% to 66% for the alkalis and was also quite comparable for MEA and NH3 as it increased from 51% to 67%. The removal efficiency for NH3 and MEA increased from 69% to 79% on average with CH4 concentration reaching over 85% volume at 40 °C. The achievable calorific value for this study ranged from 25 to 33.5 MJ/Nm3.
- Full Text:
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...
- Full Text:
- 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...
- Full Text:
Acidic catalyzed magnesium hydride and nanocomposites for hydrogen generation : synthesis and application
- Authors: Adeniran, Joshua Adeniyi
- Date: 2019
- Subjects: High pressure chemistry , Biomass conversion , Biomass energy
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/443731 , uj:38755
- Description: Abstract: This study presents the successful synthesis, characterization and hydrolysis of magnesium hydride (MgH2) and MgH2 based nanocomposites for hydrogen generation, storage and wastewater treatment. The as-delivered MgH2 serves as a precursor in most of the substrates synthesized for hydrogen production and storage in this study. In addition, Mg scrap was also investigated for the same purpose. The nanocomposites were prepared by means of a ball milling process in different time spans. MgH2, germanium (Ge), lithium aluminium hydride (LiAlH4), sodium aluminium hydride (NaAlH4), magnesium (Mg) scrap were the hydrogen generation/ storage substrates used in this study. The nanocomposites from the substrates were synthesized through ball milling of the powders in argon. The phase-structural and morphological characteristics of the composites were evaluated using transmission electron microscopy (TEM), selected area diffraction (SAD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray dispersive diffraction (XRD) characterization techniques... , D.Phil. (Mechanical Engineering)
- Full Text:
- Authors: Adeniran, Joshua Adeniyi
- Date: 2019
- Subjects: High pressure chemistry , Biomass conversion , Biomass energy
- Language: English
- Type: Doctoral (Thesis)
- Identifier: http://hdl.handle.net/10210/443731 , uj:38755
- Description: Abstract: This study presents the successful synthesis, characterization and hydrolysis of magnesium hydride (MgH2) and MgH2 based nanocomposites for hydrogen generation, storage and wastewater treatment. The as-delivered MgH2 serves as a precursor in most of the substrates synthesized for hydrogen production and storage in this study. In addition, Mg scrap was also investigated for the same purpose. The nanocomposites were prepared by means of a ball milling process in different time spans. MgH2, germanium (Ge), lithium aluminium hydride (LiAlH4), sodium aluminium hydride (NaAlH4), magnesium (Mg) scrap were the hydrogen generation/ storage substrates used in this study. The nanocomposites from the substrates were synthesized through ball milling of the powders in argon. The phase-structural and morphological characteristics of the composites were evaluated using transmission electron microscopy (TEM), selected area diffraction (SAD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS) and X-ray dispersive diffraction (XRD) characterization techniques... , D.Phil. (Mechanical Engineering)
- Full Text:
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