3. Electronic Theses and Dissertations (ETDs) - All submissions
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Item An analysis of domestic solid waste management practices in Ivory Park, City of Johannesburg Metropolitan Municipality, Gauteng Province(2020) Rambuda, Konanani; Mashilo, KonananiPoor domestic solid waste management poses several risks to communities, both directly and indirectly, related to human health and environmental impacts including injury, infection, visual pollution, degrade the land and pollute the ambient air and watercourses. Ivory Park is one of the overcrowded former townships within the City of Johannesburg, Gauteng Province, that are rapidly developing due to urbanization and immigration. Overcrowding within Ivory Park has resulted in more poorly managed waste which has attracted rodents, cockroaches and flies, and deterioration of the natural environment (land, air and watercourses). Despite measures such as awareness and recycling programs that have been undertaken to address the issue, poor domestic solid waste management continues to be a problem within this township as it is elsewhere. Questionnaires, key informant interviews and field observations were conducted to investigate the drivers of poor domestic solid waste management and to determine measures to be implemented for sustainable domestic solid waste management within Ivory Park. It is demonstrated in this research study that the main source of poor domestic solid waste management includes domestic overcrowding, insufficient capacity and resources for waste management service provision, and lack of participation of the public in awareness programs and their unwillingness to pay municipal rates. The study also demonstrates the impacts of poor domestic solid waste management within the area, which include environmental pollution, illness associated with waste and pests, and the inability of the area to attract business investment. Several measures have been previously proposed to address the issue of domestic waste management in South Africa. Results from this study suggest the most important measures include the allocation of more funds towards waste management, amendment of existing waste management policy, conducting awareness programs, enforcement of municipal By-laws, timely collection of waste, increase the frequency of waste collection (i.e. twice a week), and placement of waste skips at open spaces that are prone to littering. This study highlights the different possible actions of addressing domestic solid waste management, and the need for collective efforts and participation of different stakeholdersItem Municipal solid waste management in South Africa: evaluation of waste to energy technologies for generating electricity from municipal solid waste, Gauteng Province(2019) Dlamini, Smangele Qondile“Waste-to-energy” technologies have been presented as one of the avenues to improve the management of solid waste through the recovery of waste whilst promoting a clean urban environment and increasing renewable energy generation. The Gauteng province, however, is still high and solely dependent on landfills for municipal solid waste management. Because of the concern on the depletion of the City of Johannesburg’s landfills airspace by the year 2023, increasing waste generation and greenhouse gases emission, the province has an urgent need for a better waste management strategy. This projection becomes a motivation for the identification of suitable waste-to-energy alternative avenues to manage waste in the province. This study evaluated the potential of municipal solid waste for electricity production in nine municipalities in the Gauteng province using landfill gas to energy, incineration and anaerobic digestion technologies as well as the economic viability of the waste-to-energy technologies. The LandGEM equation was used to estimate methane generation from the waste generated in each year in order to evaluate the electricity generation potential of the technologies. The levelised cost of energy, net present value and payback period methods were used to determine the economic viability of the technologies. The study also evaluated the global warming potential, acidification potential and dioxin/furan emission potential of the waste-to-energy technologies using the life cycle assessment methodology. Four scenarios were evaluated, namely scenario 1- landfill, scenario 2 - landfill with energy recovery, scenario 3 - incineration with anaerobic digestion and scenario 4 - incineration with landfill with energy recovery. Key findings revealed that the City of Johannesburg municipality has the highest waste generation potential of 2.18925×109 – 3.9103×109 kg/yr between the years 2016 to 2035 with methane generation estimates of 181700000 m3/yr (12210 ft3/min). The incineration technology is the next best and appropriate technology option for municipal solid waste management in the province in terms of waste recovery and electricity generation potential. However, from an economic point of view, anaerobic digestion technology presented itself as an economically viable waste-to-energy technology with the lowest payback period compared to landfill gas to energy technology and incineration technology. Scenario 3 (incineration with anaerobic digestion) has the highest greenhouse gas emissions in all the municipalities. This was expected as the electricity generation potential for incineration was high in all the municipalities followed by the anaerobic digestion technology with high methane generation during biological degradation of organic waste. Scenario 4 (incineration with landfill gas to energy) has the highest acidification potential compared to the other scenarios. Dioxin emission in scenario 4 (incineration with landfill gas to energy) was higher than that in scenario 2 (landfill gas to energy) and it was not surprising as dioxin are emitted through the combustion of waste. This study is very useful to policy makers, scientists and investors for decision making purposes as it could lead to optimal investment in waste-to-energy technologies.Item Investigation into harmonic compliance with respect to the harmonic impedance envelope in the South African Grid Code (SAGC) for Renewable Power Plants (RPPs)(2019) Simelane, Mxolisi IrvinThe South African Grid Code (SAGC) for Renewable Power Plants (RPPs) uses a specific method for the approximation of harmonic impedance at the Point of Common Coupling (PCC). This method assumes that the harmonic impedance as seen at the PCC is composed of a purely inductive impedance. The assumption is due to the lack of availability of accurate and complete network information. Another assumption is then made that the harmonic impedance is three times the base harmonic impedance. The purpose of this research was to prove that the SAGC (for RPPs) method of approximating the harmonic impedance is too pessimistic. This was accomplished by comparing the SAGC harmonic impedance estimation to the estimation of what will be referred to as the load aggregation method and the current injection method. The finding from this research is that a new middle ground, between the impedances calculated by the SAGC method and the actual harmonic impedance, can be determined for instances where the location of capacitors adjacent to the PCC is known. It is recommended that the SAGC (for RPPs) approximation method be revised to make provision for instances where information regarding the location of capacitances in the network is available.Item Realisation of AD hoc renewable rural power systems with decentralised active power dispatch techniques(2019) Lange, Jarren HiltonAd hoc power systems offer a promising opportunity to provide affordable reliable renewable energy to rural areas. Classical grid solutions are impeded by low population densities and poor economic conditions that perpetuate energy poverty in large areas of rural Africa. Existing islanded renewable energy based solutions can not typically be expanded at will as the needs of its users increase. Scalable power systems, that can lower the engineering costs of commissioning and modifying the system represents a potential solution to energy poverty. Existing solutions rely on the ability to tightly model and control all elements a result of the stringent requirements imposed on these systems. Meaning scalable power systems are theoretically unrealisable. Thus, this is a system architecture and control issue, not a generation or storage issue. This thesis explores ways to realise low cost scalable power systems for low (> 1 kW) to medium (< 1 MW) power requirements. Allowing power system parameters to indefinitely deviate from nominal values, which discards a 140 year old assumption, is achievable in new electronic generation based power systems. This allows all system elements to contribute towards system operation without additional communication. Modelling is presented which simplifies complex power interactions in AC systems to passive circuit components. The desired characteristics of each element while utilising existing technologies can be identified from this modelling. These techniques, which are demonstrated and verified on a hardware based power system simulator, enable scalable economically feasible renewable power systems. This provides a novel, flexible and robust alternative to existing power systems that enables the affordable decentralised ownership and operation of renewable power systems at a household level.Item Energy and resources recovery from gasified screenings and toxic sludge(2018) Bunge, Humelton SiviweSludge and screenings management has been and is increasingly becoming a dilemma in recent decades due to increasing population and accumulation of toxins in wastewater sludge, caused by complex toxins in industrial, hospital, residential, agricultural and other effluents. Various sludge management options have been researched, ranging from incineration, thermochemical liquefaction, to pyrolysis and gasification. This work proposes syngas, bio-oil and bio-char or char production through gasification of a mixture of sludge and screenings at different ratios of 25/75, 50/50 and 75/25. Triplicate samples of each ratio were produced from sludge and screenings that were collected from Olifantsfontein, Gauteng, South Africa. The analysis to find the toxins, metals resources in sludge, approximate analysis, CHNS and functional group analysis were aimed at finding if sludge is a good high energy matter. From a thermogravimetric analysis (TGA), the sampling and stopping temperatures during gasification were established. The overall best results of high syngas quality (high LHV, H2, CO and CH4 contents) and high quality bio-oil (i.e. cleanest, with high crude oil equivalent bonds such as C1 up to C36 and higher applicable bio-oil resources and chemical names obtained) was achieved by a 75/25 ratio, followed by a 50/50 ratio. The results also showed some possibility of biological and chlorinated hydrocarbon toxins such as polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) break down as well as reduction of sludge and screenings to about 32% of the initial mass. The application of these results range from syngas application in power generation, to liquid fuel production through the Fischer-Tropsch synthesis (FTS). Char toxicity can be further analysed for its application in agriculture and as an adsorbent in other processes. Char can also be further analysed for metal extraction.Item Determinants that influence renewable energy investments(2018) Wrigley, CharleneThe Kyoto Protocol, Global Climate Change Agenda and imperative to reduce greenhouse gas emissions has gained significant traction recently as decision makers attempt to mitigate the impacts of climate change. Energy that is produced from non-renewable energy sources, such as fossil fuels, is a significant contributor to greenhouse gas emissions, and by displacing non-renewable energy production and consumption with renewable energy production, greenhouse gas emissions can be reduced. This is particularly relevant to the mining industry, which is a significant consumer of energy, particularly energy from non-renewable fossil fuel sources. Consumption of renewable energy for mining related activities presents a cost saving opportunity for the industry and could support mitigating the effects of climate change. This research aimed to identify the main determinants that influence decisions in energy investment projects, and specifically, to determine the most influential determinant in energy investment decisions, particularly in the mining industry. Through interviews of subject matter experts in the mining industry, sustainable development, renewable energy and renewable energy project investment and finance, the results suggest that Life of Operation, i.e. life of mining asset or operation, was the most influential determinant in making energy investment decisions. Security of Energy Supply in which cost, reliability and availability are secured through the energy investment closely follows as the second most influential determinant. The Global Climate Change Agenda may create an enabling environment for renewable energy investments, however the key drivers in such decisions are the financial aspects of the investment.Item The implications of the rise of clean energy on lithium market dynamics(2018) Jackson, Martin RobertThis research aims to assess the factors surrounding the emergence of markets with the greatest potential for rechargeable lithium battery adoption. The implications of the rise of electric vehicles and electrical energy storage are measured against lithium supply and market pricing. This was resolved by reviewing all available information and comparing it with the intricacies of resources, production and recycling. An analysis of price formation is also undertaken before making assumptions to enable a forecast of future market dynamics until 2030. Electric vehicles will require almost threefold the lithium produced in 2015 by the end of the period considered, with grid storage predicted to follow suit. No geological supply constraints were found, but economic scarcity is a strong possibility. Production is highly vulnerable to disruption due to concentration and the situation is exacerbated by inelastic demand. Recycling may be the most critical means of diversifying and improving supplies.Item Production of biogasoline from waste cooking oil as an environmentally friendly alternative liquid fuel(2017) Bridgiliah, Mampuru MadinogeEnergy is an important utility to human kind. Since the beginning of human civilization, human beings have become acquainted with travelling and transportation of goods. The use of conventional energy fuels for automobile engines is no longer sustainable due to finite crude oil reserves available in the world, of which many are facing the crisis of being depleted. The use of conventional fuels is a major contributor to environmental concerns such as global warming. Therefore there is an urgent need to explore alternative sources of fuel energy that are sustainable and environmentally friendly. The production of biofuels has been receiving increased academic and industrial attention as practical alternative fuel sources that can partially or completely replace conventional fuels. A study of the production of biogasoline from waste cooking oil as an alternative and re-usable source of liquid fuel was conducted in this project. This work focused on the variety of parameters that would deliver the optimum conversion and yield of biogasoline. The waste cooking oil was converted through catalytic hydrocracking in the presence of an acid activated Ni-Mo/Al2C>3 catalyst and constant hydrogen gas pressure of 0.5 kPa. A number of Ni-Mo/A^Oa catalysts were synthesized with varying Ni-loadings from 5-25 wt. % and calcination temperatures from 300 °C to 700 °C. The catalysts were characterised using ICP-OES, TGA, BET, SEM, FT-IR and Raman spectroscopy. Catalyst characterisation results revealed that the catalyst with 5 wt. % Ni possessed the greatest thermal strength, with the maximum BET surface area of 61.61 m /g and high dispersion of the active species in the catalyst. The optimal calcination temperature range for this catalyst was found from 500 °C to 600 °C. The effects of reaction temperature, reaction time, catalyst: oil ratio, catalyst calcination temperature and Ni-loading (wt. %) were investigated. The highest percentage of produced biogasoline was 59.50 wt. % at a reaction temperature of 250 °C, catalyst: oil ratio of 1:75, reaction time of 1 hr with a catalyst loaded with 5 wt. % Ni and calcinated at 300 °C. The use of stainless steel reactors that can handle higher reaction temperatures and pressure is recommended for future studies that will allow more severe cracking of the raw material into lighter hydrocarbons. The Ni-Mo/AhCT catalyst can also be modified with boron or fluorine to enhance its catalytic activity.Item Mitigating exclusionary greening of South African cities through participation of indigent households in renewable energy: the case of Galeshwe settlement in Sol Plaatjie municipality, South Africa(2018) Tyabashe, NomondeBased on the Sol Plaatje Municipality case study, this study focuses on how an innovative municipal business and funding approach could serve as a tool for transitioning from fossil fuels to renewable energy (solar) for the benefit of both indigent households and the municipality. Primary data from the municipality and indigent households in Galeshewe settlement indicates that in its current form, the 50kWh free basic electricity that indigent households receive monthly from the municipality is insufficient for their basic energy needs, while purchasing additional electricity is becoming increasingly unaffordable. This results in suppressed demand for the households and ongoing risk to the municipality due to escalating costs. In mitigation of the two fundamental challenges, findings from primary and secondary data have guided the study to the Renewable Energy for Low Income Earners (RELIE) model. The Equitable Share Grant and Integrated National Electrification Programme Grant (as currently allocated to municipalities by National Treasury and the Department of Energy for free basic electricity and electricity infrastructure provision for low income households) are highlighted as the initial funding channels under the proposed model based on a backcasting approach. Municipal energy plans and policies as well as integrated human settlements’ spatial plans also emerge as critical tools for transitioning to inclusionary RE. Other funding sources in the RELIE model include existing government funds such as the Green Fund and the Central Energy Fund from the Department of Environmental Affairs, as well as supplementary funds from relevant agencies such as climate funding entities and philanthropic socially responsive investments. The model also envisages end-user contribution through affordable payments for service. In conclusion, the study recommends that the RELIE model findings could be adapted for other municipalities in South Africa faced with the escalating indigent household energy crisis.Item Dark fermentative biohydrogen production using South African agricultural, municipal and industrial solid biowaste materials(2017) Sekoai, Patrick ThabangThe dwindling fossil reserves coupled with environmental pollution necessitate the search for clean and sustainable energy resources. Biohydrogen is emerging as a suitable alternative to fossil fuels and has received considerable attention in recent years due to its economic, social, and environmental benefits. However, the industrial application of biohydrogen has been hindered by low yield. Therefore, development of novel techniques to enhance the yield is of immense importance towards large-scale production of biohydrogen. Thus, this research effort explored various options to enhance the yield of biohydrogen during dark fermentation process. Some options explored included (i) the utilization of feedstocks from the agricultural, industrial and municipal sectors, (ii) parametric optimization of biohydrogen production, (iii) investigation of biohydrogen production using metal ions and nitrogen gas sparging, and (iv) assessing the feasibility of biohydrogen scale-up study to pave the way for pilot-scale development. Solid biowaste feedstocks consisting of apple, bread, brewery residue, cabbage, corn-cob, mango, mealie-pap, pear, potato, and sugarcane were investigated for dark fermentative biohydrogen production using anaerobic mixed sludge. The experimental results showed that substrates which are rich in carbohydrates are suitable for dark fermentative biohydrogen-producing bacteria. Consequently, a maximum biohydrogen fraction of 43.98, 40.32 and 38.12% with a corresponding cumulative biohydrogen yield of 278.36, 238.32 and 215.69 mL H2/g total volatile solids (TVS) was obtained using potato, cabbage, and brewery wastes, respectively. Based on these results, potato waste was chosen as a suitable substrate for subsequent biohydrogen production studies. Parametric optimization was carried out on biohydrogen production via dark fermentation using potato waste as the substrate. Effects of operating variables such as pH, temperature, fermentation time, and substrate concentration were investigated via response surface methodology (RSM) approach using a two-level-four factor (24) central composite design (CCD). The obtained predictive model (statistical model) was used to explain the main and interaction effects of the considered variables on biohydrogen production. In addition, the model was employed in the optimization of the operating conditions. Consequently, a secondorder polynomial regression with a coefficient of determination (R2) of 0.99 was obtained and used in the explanation and optimization of operating variables. The optimum operating conditions for biohydrogen production were 39.56 g/L, 5.56, 37.87 oC and 82.58 h for potato waste concentration, pH, temperature and fermentation time, respectively, with a corresponding biohydrogen yield of 68.54 mL H2/g TVS. These results were then validated experimentally and a high biohydrogen yield of 79.43 mL H2/g TVS indicating a 15.9% increase was obtained. Furthermore, the optimized fermentation conditions were applied in the scale-up study of biohydrogen production that employed anaerobic mixed bacteria (sludge) which was immobilized in calcium alginate beads. A biohydrogen fraction of 56.38% with a concomitant yield of 298.11 mL H2/g TVS was achieved from the scale-up study. The research also investigated the influence of metal ions (Fe2+, Ca2+, Mg2+ and Ni2+) on biohydrogen production from suspended and immobilized cells of anaerobic mixed sludge using the established optimal operating conditions. A maximum biohydrogen fraction of 45.21% and a corresponding yield of 292.8 mL H2/g TVS was achieved in fermentation using Fe2+ (1000 mg/L) and immobilized cells. The yield was 1.3 times higher than that of suspended cultures. The effect of nitrogen gas sparging on biohydrogen conversion efficiency (via suspended and immobilized cells) was studied as well. Cell immobilization and nitrogen gas sparging were effective for biohydrogen production enhancement. A maximum biohydrogen fraction of 56.98% corresponding to a biohydrogen yield of 294.83 mL H2/g TVS was obtained in a batch process using nitrogen gas sparging with immobilized cultures. The yield was 1.8 and 2.5 times higher than that of nitrogen gas sparged and non-sparged suspended cell system, respectively. Understanding the functional role of microorganisms that actively participate in dark fermentation process could provide in-depth information for the metabolic enhancement of biohydrogen-producing pathways. Therefore, the microbial composition in the fermentation medium of the optimal substrate (potato waste) was examined using PCR-based 16S rRNA approach. Microbial inventory analysis confirmed the presence of Clostridium species which are the dominant biohydrogen-producing bacteria. The results obtained from this research demonstrated the potential of producing biohydrogen using South African solid biowaste effluents. These feedstocks are advantageous in biohydrogen production because they are highly accessible, rich in nutritional content, and cause huge environmental concerns. Furthermore, optimization techniques using these feedstocks will play a pivotal role towards large-scale production of biohydrogen by increasing throughput and reducing the substrate costs which accounts for approximately 60% of the overall costs. The findings from this research also provide a solid basis for further scale-up and techno-economic studies. Such studies are necessary to evaluate the competitiveness of this technology with the traditional processes of hydrogen production. In summary, the findings from this research effort have been communicated to researchers in the area of biohydrogen process development in the form of peer-reviewed international scientific publications and conference proceedings, and could provide a platform for developing an economic biohydrogen scaled-up process.
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