Theses and dissertations (Engineering and Built Environment)

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Anaerobic co-digestion with industrial wastewater for biomethane production
(2020-10-20) Adedeji, Jeremiah; Chetty, Maggie
The increasing demand for energy has led to the utilization of fossil fuels more abundantly as a quick alternative for generation of energy. The use of these sources of energy however as led to the generation of greenhouse gases which tend to cause climate change, thus affecting the ecosystem at large. Thus, there have been the search for alternative sources which cannot be depleted but do generate minimal greenhouse gases. One of such alternate sources is industrial wastewater which have shown to have high concentration of nutrients in the form of organic contents which can be converted by micro-organisms into energy, usually known as biogas, comprising majorly of CH4, CO2 and H2. Another important factor is that industrial wastewaters are a renewable energy source which are continuously generated due to increasing urbanisation and population growth. In this study, the characteristics of three agro-industrial based wastewaters used shows their potential for application in anaerobic co-digestion”. Anaerobic co-digestion method was utilized to harness the synergetic effect of both sewage sludge and agro-industrial wastewater as co-substrate for the generation of biomethane. The result of the effect of varying mix-ratio of the substrates on biomethane production of sugar wastewater and dairy wastewater indicated that mix-ratio of 1:1 for sewage sludge to sugar wastewater operated at 35oC was suitable for optimum generation of biomethane of 1400.99 mL CH4/g COD added and COD reduction of 54%. The model generated using design expert was found to navigate the design space and could perfectly predict the yield of biomethane effectively for the sugar wastewater mix. The biomethane potential tests (BMP) experiment using varying inoculum-substrate ratio (ISR) showed that operating at mesophilic temperature of 25oC with ISR of 1:2 and 2:1 for sugar wastewater and dairy wastewater respectively does increase the methane production within the first three (3) weeks. The kinetic models that best fit the anaerobic co-digestion for sugar wastewater was the first order model while the simplified Gompertz model favoured the dairy wastewater perfectly. The biomethane potential tests indicate significant increase the biomethane production and as well reduction in the volatile solid and chemical oxygen demand (COD) content. In conclusion, both sugar and dairy wastewater can be recommended as co-substrates for anaerobic digestion of sewage sludge for increased and improved biomethane production while simultaneously reducing their COD content at the same time.
The analytical and experimental study on the establishment of a tidal power plant in South Africa
(2021-02) Mtukushe, Namhla Faith; Ojo, Evans Eshiemogie
The majority of South Africa’s electricity is generated from fossil-fuel plants that use mainly coal. In these power plants, the combustion of these fossil fuels liberates greenhouse gasses into the atmosphere that contribute to climate change. This problem coupled with the rapid depletion of fossil fuels has necessitated the need to explore the alternative form of energy such as renewable energy. Tidal energy is a form of ocean energy that can be considered as an alternative energy resource or renewable energy source. This form of energy has not been explored in South Africa, the only country in the world that is bounded by two oceans; the Indian and the Atlantic. Tidal energy can be harnessed from the movements of tides to generate electrical power. This study considered the possibility of harnessing tidal energy as the alternative energy source for power generation which can be used to mitigate the challenges associated with the energy crisis currently being experienced in the country. For this study, an extensive literature review was carried out to understand the tidal phenomenon, the concept of energy conversion from tides, the different techniques or technologies that can be used to generated power from tides. There are two main technologies used for converting tidal energy to electrical energy and these are the tidal barrage and the tidal streams. Based on the inferences drawn from the literature reviews concerning the tides experienced around the South Africa coastal region, it was identified that the tidal stream technique is applicable. Harmonic analysis of the tidal resource for four identified sites was conducted, from these analyses, Esikhawini was selected as an optimum site. Tidal streams extract the kinetic energy of tides and the mode of operation of tidal stream plants is determined by the type of tidal turbine employed. Several turbine designs were reviewed, a helical cross-flow turbine was selected due to its self-starting capability and its ability to operate in reverse stream flows. For this helical turbine, an analytical model using the blade element momentum theory (BEMT) was developed and was implemented on MATLAB environment. For the experimentation, a prototype was developed and tested in a laboratory concrete flume in the department of Civil Engineering at the University of KwaZulu-Natal. Based on the experimental results, an analysis of the unit turbine was done which was used to propose a conceptualized tidal power plant. Hence, the proposed tidal power plant was used to justify the reason for embarking on this study which is to ascertain the possibility of establishing a tidal power plant in South Africa.
Appraisal and optimization of energy-efficient green buildings in South Africa
(2024-05) Agbajor, Favour David; Mewomo, Modupe Cecilia
Generally, over 35% of global energy use and 40% of carbon emissions are attributed to the built environment while future forecasts indicate that these values may rise much further. In South Africa (SA), building stocks account for 40% of the country’s final energy demand which strains the country's coal-dependent energy grid and oftentimes results in power outages. Optimizing energy efficiency and thermal comfort while attaining the lofty goal of carbon neutrality is essential for all concerned stakeholders in the building sector globally. Meanwhile, green building (GB), being a recognized revolutionary theory and practice in the building industry, is suggested as a solution to SA’s environmental challenges. On this wise, this research aimed to develop energy-efficient models for optimizing green buildings into the design and operation of buildings to allay their environmental impacts. The goal was to enhance energy efficiency, decrease energy consumption, and mitigate carbon emissions across diverse climates, thus benefiting South Africa's built environment. To achieve the study's goals, three primary research objectives were identified and pursued namely: (i) To provide an overview on status-quo of green building development in South Africa with a view to explore the status quo and provide roadmap for improvement; (ii)To examine the energy-saving potential of incorporating building-integrated greenery systems towards climate-resilience in the subtropical climate zone of South Africa; and (iii) To investigate the energy-performance of green building renewable energy utilization systems within South Africa’s hot and arid climate zones. Initially, the study's first objective entailed a comprehensive literature overview integrating climate, sustainability, and building energy modeling within the South African context. This was carried out through a scoping review approach via the PRISMA guideline of reporting Subsequent objectives involved selecting reference buildings and creating hypothesized models as case studies based on six climate zones from the South African National Standard. For the second objective, a thorough and integrative approach that linked building energy modelling and varying climatic change was devised. The numerical parametric simulation and analysis, being a quantitative research approach was adopted as a data collection method. Similarly, the third objective employed numerical parametric simulation as a data gathering method in this research, which is based on a quantitative analysis to explore various design options iteratively. In the second and third objectives, Global climate databases, Meteonorm, Climate Consultant, and energy simulation software such as DesignBuilder, EnergyPlus, and Polysun were used for weather data analysis, climate modeling, and building energy simulation. The findings highlighted that while South Africa boasts notable green construction projects, scientific research progress has not matched international levels. The focus was on promoting green building adoption through standards, certifications, and incentives. However, gaps were observed in optimized energy performance and post-occupancy evaluation of existing buildings. Despite high awareness, the utilization of green building technologies among South African professionals did not meet anticipated levels. For the second objective, the study's findings indicated an increase in extreme heat waves with higher peak temperatures in the future. Building energy use in the study area is projected to rise by 8-24% from 2030 to 2080. Notably, heat gains primarily result from envelope thermal transfer rather than solar radiation. Greenery systems were found to effectively support green building goals and urban sustainability across anticipated seasons. Nature-based solutions proved successful in adapting to climate change compared to non-retrofitted conventional buildings. For the last objective, the study revealed regions with substantial solar irradiance, indicating potential for renewable energy adoption. It emphasized the need for durable BIPV systems in hightemperature conditions. BIPV modules generated more energy in Upington than Nelspruit due to varying solar radiation. Opportunities were identified for BIPV systems to achieve optimal power generation. The study provides a foundation for informed decision-making, policy formulation, and targeted research in sustainable building practices. The study presents practical principles to guide urban planners and policymakers in integrating eco-friendly technology into both new and existing building designs. This promotes sustainable urban development and reduces cities' carbon emissions. Going forward, to showcase the effectiveness of these energy-efficient and climate-responsive systems to the public and industry stakeholders, it is recommended to establish and enhance largescale demonstration projects in South Africa's subtropical, hot and arid regions.
Architectural considerations and resource allocation in energy efficient networking
(2022-09-29) Molefe, Mlungisi; Nleya, Bakhe
Word-wide data traffic is continuously surging, triggered mainly by the emergence of Internet-of-Things (IoT)’s services and Fog-Cloud computing-based applications. This calls for existing optical and wireless-based network infrastructures to upgrade capacity accordingly to meet required massive bandwidth demands to accommodate the ever-surging data traffic volumes. However, continuously elevating the resource requirements in terms of bandwidth provisioning implies increasing the number of en-ergy-consuming network elements, which will increase overall operational expendi-tures and carbon footprint due to extra power generation. Carbon emissions contribute significantly to global warming. To avert this, it has become necessary to promote en-ergy-efficient networking. For that reason, it necessitated an emphasis on energy effi-ciency in the design, operation, and planning of transport networks. The current dense wavelength division multiplexing (DWDM) based optical transport network architectures operate with fixed-grid employing fixed data rates. So, making this rigid approach to capacity allocation leads to inefficiencies in both spectrum allo-cation and energy usage. Flexible (or elastic) optical transport networks with flexible-grid were proposed to improve bandwidth provisioning efficiencies. Such networks support adaptive line rates and OFDM-based optical transmission, thus, this will lead to lesser network elements deployed and, consequently an improvement in energy ef-ficiency. Similarly, wireless networks, whose data traffic is mostly derived from de-vice-to-device (D2D) communication and heterogeneous 5G cellular networks (HET-NETs) have since made tremendous strides to further enhance bandwidth by way of overlaying multiple types of low power small cells in a high-power macro cell. They afford more opportunities to explore the potential cognition and cooperation diversi-ties to improve spectral efficiency. Thus in this work, we focus on both architectural design and operation of wireless and optical transport networks coupled with resource allocation. A model joint all photonic and wireless transport network architecture framework is proposed and analyzed. The architecture’s performance in servicing high-capacity mobile back-haul and front-haul traffic and real-time services support is evaluated by both analytical and simulation approaches. Various routing and switching scenarios are considered. Overall, results demonstrate that elasticity allocation of resources (bandwidth) can vastly improve the network performance in terms of spectral efficiency, reduced locking probability, and enhanced end-to-end network throughput.
An assessment of the impact of selected construction materials on the life cycle energy performance and thermal comfort in buildings
(2021) Haripersad, Rajesh; Lazarus, Ian Joseph; Singh, Ramkishore; Aiyetan, Olatunji Ayodeji
South Africa is a developing country with various construction projects that are being undertaken both by government and the private sector. The requirements for the construction of energy-efficient buildings as well as the selection methods for providing construction materials have hence become important. Energy efficiency improvements needs to be implemented in the construction of these buildings in order to decrease energy usage and costs and provide more comfortable conditions for its occupants. Previous studies revealed that most of the focus for improving energy efficiency in buildings has been on their operational emissions. It is estimated that about 30% of all energy consumed throughout the lifetime of a building is utilized as embodied energy (this percentage varies based on factors such as age of building, climate and materials). In the past this percentage was much lower, but with increased emphasis placed on reducing operational emissions (such as energy efficiency improvements in heating and cooling systems), the embodied energy contribution has become more significant. Hence, it is important to employ a life-cycle carbon framework in analysing the carbon emissions in buildings. The study aims to augment energy efficiency initiatives by showcasing energy reduction strategies for buildings. The study assessed the thermal performance of selected construction materials by analysing different buildings using energy modelling program, EnergyPlus and TRNSYS. The parametric study was set in the central plateau region of South Africa and was performed to determine appropriate energy efficiency improvements that can be implemented for maximum savings. A life cycle cost analysis was performed on the selected improvements. The models created are representative of the actual buildings when simulated data is compared to recorded data from these buildings. Results showed a significant variation in energy and construction costs with varying construction materials over the buildings’ life cycle. Findings suggest that there is a significant reduction in energy usage when simple efficiency measures are implemented. The study recommends the use of different energy efficient building materials and the implementation of passive interventions in the constructing of buildings; the thermal performance of a building be optimized to ensure thermal comfort and the developed model be adopted for use in the engineering and construction industry for the reduction of energy consumption.
Characterisation of concrete with expanded polystyrene, eggshell powder and non-potable water : a case study
(2023-05) Mncwango, Bonke; Allopi, Dhiren
Urbanisation has brought many benefits but it has also highlighted the global lack of housing alongside global natural resource scarcity. Lack of housing on the surface appears to be a singular problem, however in reality it represents a number of society’s biggest challenges such as crime, pollution (as a result of inadequate waste disposal strategies), unhygienic living conditions, as well as numerous health problems. Governments across the world have made various attempts at addressing the issue of lack of housing, including embarking on large scale social and public housing initiatives, building smaller homes for the homeless, as well as removing certain regulatory barriers to allow more houses to be built at a reduced timeframe. These advances have assisted many individuals and families globally, however, there are still many individuals and families that government housing-aid or housing initiatives have not yet reached. These individuals and families are faced with solving their housing crisis on their own, with their own resources. Globally, concrete remains a supreme building material in the construction industry and therefore is a primary factor of consideration for solving the housing crisis, especially for those who have no financial assistance or aid from government. Concrete’s composition is simple: cement, fine aggregate, coarse aggregate and water. The intricate interaction between all four components is meant to stand the test of time. Unfortunately, it is not only the earth’s diminishing natural resource reserves which are causing a decline in the popularity of conventionally produced concrete, but it is also the irreparable harm that it is causing to the environment. The process of concrete production requires large volumes of cement, and cement remains one of the biggest producers of carbon dioxide. Carbon dioxide is a greenhouse gas which in excessive amounts creates a cover that traps the sun’s heat energy in the atmosphere. Another major criticism of conventional concrete is the requirement that it be produced with clean water which is of a drinkable standard. This criticism is justified when considering the extreme water shortages that are experienced by many low to middle income countries around the world. The amount of financial and human resources that local authorities invest in cleansing water to bring it to a drinkable standard is often overlooked. It is obvious that it is less expensive to use water directly from a river in its natural state than using it after it has undergone numerous cleansing processes by local authorities. There have been a notable number of advances in making concrete more resource-efficient and environmentally friendly. These include the advent of lightweight concretes such as expanded polystyrene concrete. Expanded polystyrene concrete not only saves the amount of aggregate that would normally be required in conventional concrete, it also has excellent acoustic and thermal properties, thereby reducing energy consumption which in turn saves money. However, even with such excellent properties, expanded polystyrene concrete still fails to address two of concrete’s major criticisms which are related to the amount of cement used as well as the amount of clean potable water required for mixing. Therefore, by building on the qualities of expanded polystyrene concrete, this research investigates the potential of lowering the amount of cement required in a concrete mix through the use of eggshell powder. Eggshells are a waste product found everywhere in the world and are readily available in almost limitless quantities. The use of eggshells in concrete to lower the amount of cement required will not only achieve a reduction in the amount of carbon dioxide that is produced in the process of producing concrete, it will also assist in contributing toward solving the escalating waste disposal crisis that currently exists for many waste types such as eggshells. It is common for communities to reside close to a river or a natural flowing watercourse, so this research included river water as a variable. Four different concrete mix scenarios were tested to ascertain through experimentation whether the strength properties of concrete that contains expanded polystyrene, eggshell powder and natural river water in various proportions could in any way compare to a conventionally produced concrete mix. In order to comprehensively study material behaviour in this case, sieve analysis, bulk density, fineness modulus, moisture content as well as specific gravity tests were performed on all aggregates used. Furthermore, in order to achieve the required analytical depth for the materials being studied, x-ray diffraction and energy dispersive spectroscopy tests were conducted. As a means of conducting further trend analysis on the different experimental mixes, logarithmic regression models were developed. Through analysis of the output attained from the aforementioned strategies, this research study found that when cement was substituted by eggshell powder at a percentage of 5 % and simultaneously when coarse aggregate was also substituted by expanded polystyrene at a percentage of 5 %, all mixed with non-potable water, the compressive and flexural strength outcomes marginally differed from the strength outcomes of conventionally produced concrete. Furthermore, the substitution of stone by EPS at a percentage of 10 % when mixed with river water was comparable to the substitution of stone by EPS at a percentage of 10 % when mixed with potable water. The results showed that there was a difference of not more than 1.4 MPa and 0.3 MPa in compressive and flexural strength respectively amongst the averages obtained at each age tested. Study results show that the substitution of potable water by non-potable water reduced both the compressive and flexural strength of the concrete when the mix did not contain eggshell powder. However, when eggshell powder was included in the mix, the strength outcomes of the compressive and flexural strength of the concrete mix was comparable to that of conventionally produced concrete. There may be many reasons why it is important to not deviate from convention in the production of numerous products such as concrete; nevertheless, the value of experimentation as demonstrated in this research is that experimentation can give rise to a variety of innovations accompanied by a wealth of solutions to the environmental and socio-economic issues that the world is currently faced with.
Coordinated control of conventional power sources and plug-in hybrid electric vehicles for a hybrid power system
(2022-05) Adbul-Kader, Mohammed Ozayr; Akindeji, Timothy Kayode; Sharma, Gulshan
Globally, the requirement for renewable and clean energy technologies is becoming vastly popular. With the high implementation of solar and wind energy systems, together with plugin hybrid electric vehicle (PHEV) aggregators, energy costs can be minimised, greenhouse gas emissions decrease, and overall maintenance becomes reduced. The constant increase of load demand is becoming a challenge for the current power systems, with difficulties including stability concerns and excessive regulations by the government. Due to irradiance and wind speed fluctuations, the solar and wind energy system’s non-linearity affects the existing power system stability. The growth of the electric vehicle industry has also shed new light on potential auxiliary services that can be provided, as and when required, to the power system. Hence, this research examines the potential control strategies that are required to maintain the system in steady-state conditions after disturbances that occur with higher penetration of renewable energy systems (RESs) and PHEVs. The case study models a isolated two-area thermal type power system that is interconnected through an AC tie-line. Three scenarios are modelled, simulated and analysed. The first scenario models a isolated thermal power system with PHEVs with two areas which utilises a fractional order proportional integral derivative (FOPID) controller in each area. The resulting model is analysed to see the effects of PHEVs coupled with FOPID on the power system. The second scenario models a isolated two-area thermal power system with RES and utilises a fuzzy type-2 (FT2) FOPID controller in each area. The RES penetration istested for its non-linearity effect on the isolated power system, and the error is reduced by an advanced controller that uses artificial intelligence techniques. The third scenario is modelled as an isolated two-area thermal power system with PHEVs and RES coupled with neural network predictive controller (NNPC) in each area. The three scenarios are simulated in MATLAB/Simulink with results displayed graphically and numerically. The results show that the integration of PHEVs for load and/or storage in the multi-area power system, and the proposed control methods for each scenario, have the best dynamic response with the least error, no oscillations and the fastest response to steady state condition.
Designing a stormwaterharvest system in new smart cities in KwaZulu-Natal, South Africa
(2024-05) Mukome, Bwija
The nexus between climate change and water management represents one of the contemporary challenges confronting economic development and sustainable livelihoods in many cities the world over. Thus, assessing the impacts of climate change for evolving smart-city water management, especially for a country like South Africa that is classified as a “water-stressed” country, constitutes an innovative way to water management. This study aimed at proposing an alternative water supply augmentation source that is sustainable for new smart cities under different climatic scenarios within the KwaZulu-Natal Province of South Africa. The specific objectives of the study were to assess the impacts of climate change and the imperativeness of a sustainable and efficient stormwaterharvesting (SWH) system in the new smart city; determine the social, economic and technical barriers to an efficient SWH system; evaluate the technical and financial feasibility of stormwaterharvesting system integration in smart cities; and design a prototype sustainable and efficient pilot-scale engineering SWH system. To address these objectives, the aggregated views of stakeholders within the Water/ Climate change sector were solicited through questionnaires and interviews collected data were analysed using a statistical package and thematic classification. The triangulation method was used to justify acceptable opinions where both the qualitative and quantitative responses were in opposing positions. The standardised rainfall anomaly index (SRAI), simple precipitation ratio (SR), coefficient of variation in rainfall distribution (CV), precipitation concentration index (PCI), and the seasonal precipitation index (SPI) were used to evaluate the impacts of climate change on rainfall variability; whilst different inferential statistics techniques like Mann Kendal, Sen slope, regression, correlations, multifactor analysis (MFA), and chi-square test values- interpreted using the p-values- were used to identify the abrupt changes, trend patterns and significant impacts of climate change on the hydrological water balance for the study area, which in turn influenced decision-making in designing a new smart city. Based on a monthly water balance evaluation, the technical and financial feasibility of stormwater harvest system integration in smart cities was thematically deduced from survey interviews conducted and validated with simple component costing for SWH design and operation. The design of a sustainable and efficient pilot-scale engineering SWH system was synthesised through an extensive literature review for future adaptation. The various analyses and results in ranking the socio-economic and technical barriers to SWH system integration into smart cities connotes ageing infrastructure; the lack of proactive maintenance; and a lack of finance as the biggest challenges to efficient stormwaterharvesting system implementation. The study concludes that SWH presents a viable alternate source for water that might improve urban water self-sufficiency sustainability under different climatic smart city assessments, whilst recommending capacity development where climate change experts transfer knowledge, skills and expertise to upcoming researchers.
Development of a multi-criteria decision-support tool for improving water quality to assist with engineering infrastructure and catchment management
(2024-05) Ngubane, Zesizwe; Sokolova, Ekaterina; Stenström, Thor-Axel; Dzwairo, Bloodless
Research combining water quality modelling, quantitative chemical/microbial risk assessment, and stakeholder engagement to prioritise catchment areas facing water pollution problems to devise effective pollution mitigation strategies are limited. This research therefore aimed to address this gap by providing a practical and comprehensive framework that supports wellinformed decision-making processes in water pollution alleviation. By integrating multiple criteria and catchment aspects, this framework can assist infrastructure, operational, and ecological managers within a catchment in prioritising best management practices (BMPs) to reduce pollution and mitigate against potential resultant impacts. Given this context, uMsunduzi catchment, in KwaZulu-Natal, South Africa was chosen as a study site. UMsunduzi River is a major tributary of uMngeni River that is used for water supply to the cities of Pietermaritzburg and Durban. The study begins with the data synthesis from diverse sources of scientific data to identify chemical and microbial hazards, utilising a water quality modelling tool to map point and nonpoint source pollution in the catchment. The assessment encompasses the presence of pathogens such as Cryptosporidium and Escherichia coli (E. coli) in the catchment, with rural areas showing a greater contribution from animal sources, while urban areas are affected by impaired wastewater infrastructure. Quantitative microbial risk assessment (QMRA) was conducted, assuming no water treatment within the catchment. The investigation considered multiple exposure routes, including domestic drinking and recreational activities for both adults and children. The results indicate that the probability of infection from Cryptosporidium and E. coli exceeds acceptable levels set by South African water quality guidelines and the World Health Organization. The assessment further included a chemical risk assessment on various chemical groups, including organochlorinated pesticides (OCPs), pharmaceuticals and personal care products (PPCPs), heavy metals, nitrates, and phosphates. Elevated carcinogenic risks were observed for most OCPs, while noncarcinogenic pesticide effects pose long-term risks. Heavy metals and PPCPs are within sub-risk levels, but phosphates have notable ecological and health impacts, particularly in Inanda Dam, a key source of potable water for Durban. In this study, a unique contribution is made by incorporating both chemical and microbial risk assessment. Furthermore, the risk assessment methodology not only encompasses various chemical pollutants and exposure pathways but addresses the nuanced issue of water consumption variability between children and adults. To address these identified risks, a multi-criteria decision analysis methodology is employed to engage stakeholders in the risk management process. Affected, involved, and interested stakeholders, along with economic, environmental, and social criteria, contribute to the selection of Best Management Practices (BMPs). The Simple Multi-Attribute Rating Technique for Enhanced Stakeholder Take-up (SMARTEST) is utilised to identify suitable interventions. The study culminates in the recommendation of BMPs that aim to change behaviour, including public education on livestock grazing management, safe medication disposal, and responsible fertilizer and pesticide use. Pollution management measures, such as solid waste control and river cleanup, are suggested, along with infrastructure management improvements, like sewer system maintenance. This research strived to bridge the gap in water pollution alleviation by presenting a practical and comprehensive framework designed to support well-informed decision-making processes. This framework, with its integration of multiple criteria and considerations, stands poised to aid infrastructure, operational, and ecological managers within a catchment in prioritising BMPs aimed at reducing pollution and mitigating resultant health impacts.
Development of multi-objective optimization model for project portfolio selection using a hybrid method
(2024-05) Mogbojuri, Akinlo Olorunju; Olanrewaju, Oludolapo Akanni
Selecting inappropriate projects and project portfolios can result in irreversible wasted economic opportunities, reduced manpower value, and missed prospects and other resources for the organization. As a result, to achieve the best possible outcome, all criteria to enable the best possible choices to be made should be considered. Choosing projects wisely and managing the project portfolio can assist organizations in gaining a better understanding of their projects and their risks and advantages. When faced with budget and other constraints, the ability to select an optimal mix of projects is a significant advantage in the project selection process. The selection of projects by means of employing an effective method is uncommon because many methods are deemed ineffective due to limitations on the number of projects that can be chosen, along with the failure to select economical projects. Project selection is a complex, multicriteria decision-making procedure involving numerous and frequently competing goals. The complexities of project selection problems stem primarily from the large number of projects that are required to be selected for an appropriate collection of investment projects. The study identified some research gaps such as limited studies on social sustainability benefits, criteria for public project selection not being considered or mentioned, and the decision-making committee or expert generating weight to the deviational variables instead of using weighting techniques. The aim of this study is to employ an integrated approach to establish a multi-objective optimization approach for public project portfolio selection. The specific research objectives are to develop an integrated method of Analytic Hierarchy Process, Goal Programming and Genetic Algorithm (AHP-GP-GA), establish a relationship for the developed models to correct the bias of each model and apply the integrated method in a selected community with a set of projects. Data was collected by compiling a well-structured questionnaire for decision-makers analysed by applying the AHP and GP methods. The composition of the integrated approach includes decision support tool with exact and includes meta-heuristic modelling known as Analytic Hierarchy Process, Goal Programming and Genetic Algorithms (AHP-GP-GA) for solving public project portfolio selection problems. The Analytic Hierarchy Process model was used to develop project selection criteria, assign relative priority weights of decision makers, and determine the overall weight of project alternatives. The GP constructed the mathematical model to handle large numbers of objectives and constraints. The GA is the solution algorithm for the effective and flexible optimization model to produce optimal solutions. The AHP and GA employed Spice Logic and MATLAB software packages to analyse, validate and enhance the research. The AHP model highlighted some sub-criteria and project criteria attributes that are significant to project selection criteria. These criteria are economic development, job creation, community acceptance, structure aligned with company goals, employment record of project manager, locality of the project, finish period of the project selected, project threats and political impact. Meanwhile, empirical research on public agencies was undertaken with the AHP-GP-GA, AHP-GP and GP separately to address the problem. The GP and AHP-GP used the LINGO 18.0 software package, while the developed integrated method AHP-GP-GA was solved using MATLAB software package to exhibit the competence of the model and the research. The high point of the empirical research showed that the AHP-GP-GA model can solve large-scale, or complex problems with a large number of decision variables. It selected more projects compared to the AHP-GP and GP standalone model and provided more optimal solutions, which made the approach robust and flexible for solving decision-making problems. The theoretical and practical contributions of the study are the research, which will improve the knowledge and understanding of researchers or academia in PPSP and add to the literature to enhance the existing methods of integrated approaches. The stakeholders in project management practitioners like organization management, top executives, senior and junior supervisors, and personnel connected to the projects will also benefit from the research in selecting optimal projects from the various solution options, saving costs, and learning how to handle and select more complex projects in large-scale real-life situations. This study recommends further research on the integration of stochastic models, evolutionary algorithms, or computation with AHP and GP for the Public Project Portfolio Selection Problem.
Distributed generation optimization in future smart grids
(2022-09-29) Chidzonga, Richard Foya; Nleya, Bakhe
Ever-surging global power(energy) demands coupled with the need to avail it in a reliable, as well as efficient manner, have led to the modernization of legacy and cur-rent power system grids into Smart Grid (SGs) equivalents. This is mostly achieved by blending the existing systems with an information subsystem that will facilitate duplex communication, i.e., electrical power flowing towards the end users while information characterising the grid’s performance can also be relayed, mostly in the reverse direction. Thus, the information subsystem interconnects other core (key) entities such as generation, distribution, transmission, and end-user terminals to interrelate in real-time, and in the process, achieving a well reliable, robust as well as efficiently managed SG power system. As such, in the emerging distributed power systems of the future, Demand Side Management (DSM) will play an important role in dealing with stochastic renewable power sources and loads. A near-unity load factor can be secured by employing De-mand Response methods with storage systems as well as regulatory control mechanisms. Increasing deployment of Renewable Energy generation and other forms of unconventional loads such as Plug-In Electric Vehicles will aid DR implementation with attendant better results for both prosumers and the utilities. The central objective of DSM is to minimize peak-to-average ratio (PAR) and energy costs by switching to cheaper RES as well as reduction of CO2 emissions. This work focused on emergent techniques and microgrid optimization with special attention to load scheduling. Techniques for DSM, mathematical models of DSM, and optimization methods have been reviewed. State-of-the-art methodologies entering the DSM mainstream are data science, advanced metering infrastructure, and blockchain technologies. An improved atom search optimization technique is applied for DSM to substantially reduce power and energy costs in typical standalone or grid-tied microgrids. Further the day ahead dispatch problem of MGs with DEGs subject to a non-convex cost function is solved and simulated using quadratic particle swarm optimization. In the later case, the objective function includes the DEGs ‘valve-point’ loading effect in the ‘fuel-cost’ curve. The impact of DSM on convex and non-convex energy management problems with different load participation levels is investigated. Ultimately, it is demonstrated that the quadratic particle swarm optimization algorithm efficiently solves the non-convex energy management system (EMS) problem. In addition, we propose a hierar-chical optimal dispatch framework that relies on several objectives to achieve the overall design goal of a reliable and stable power supply, coupled with economic ben-efits to prosumers who elect to participate in power trading. Evaluation of the pro-posed framework is carried out analytically and by way of simulation. Overall, it is deduced from the obtained analytical as well as simulation results that the combination of appropriately sized battery storage systems (BESS) and renewable type generators such as PVs and WTs will help achieve a stable and reliable power supply to all users in the SG (or MG) and at the same time, it affords resilience. Final-ly, in our closing chapter, we also spell out possible future research directions.
Effect of operating conditions on the hydrothermal valorisation of sewage sludge
(2021-02) Madikizela, Mbaliyezwe Precious
The accelerated population growth, in conjunction with the rapid urbanisation rate, are the principal driving forces behind the augmented volumes of municipal sewage sludge generated worldwide. The traditional approaches of sewage sludge treatment, which include landfilling and agricultural application, are no longer within the realms of possibility due to rigorous regulations, deficiency in the capacity of land available and the environmental and health adversities associated with detrimental constituents of sewage sludge. The population and urbanisation advancements do not only influence the emergent volumes of sewage sludge, but they also instigate fundamental provocations to the global energy demand. The reliance on fossil fuels poses a significant threat, not only to sustainable development, however they are also hugely responsible for the cumulative carbon dioxide and other greenhouse gas (GHG) emissions that deteriorate the environment, trigger global warming and deleteriously impact the livelihood of all life on earth. In line with the quest for sustainable and renewable alternative energy sources, the thermochemical treatment of municipal sewage sludge has a triple advantage of valorising the abundant volumes of the sludge, addressing the injurious nature of conventional fuels to the environment and seeking to bridge the gap as their supply diminishes. This study followed a quantitative approach, with the purpose to convert municipal sewage to valuable bio-oils. The sewage sludge was subjected to hydrothermal liquefaction in 60 ml stainless steel batch reactors, where the effect of temperature, solvent composition, and solvent content were investigated, and all the other process parameters were maintained at a constant. The six temperatures that were explored were 220oC, 250oC, 280oC, 310oC, 340oC, 370oC. The two solvents investigated were de-ionised water (H2O) and ethanol (E) which were applied in the following compositions: 1:0, 1:1 and 0:1 (H2O:E). The five solvent contents investigated were 75%, 80%, 85%, 90% and 95%. The process yielded bio-oils, solid phase and gaseous products and an aqueous phase. Dichloromethane was used as an extraction medium. The obtained results revealed that the temperature, solvent type and solvent content had a significant influence on the yield of bio-oil produced while temperature was the most influential out of the three parameters. When temperatures approached supercritical conditions of water, a notable decline in the bio-oil yields was observed. For each temperature, the bio-oil yields initially increased until about 85% solvent content, and then slightly decreased thereafter. The highest bio-oil yields were achieved at 310oC and the best yields were obtained when the ratio of H2O and E were 1:1. This study found that the optimum operating conditions were obtained at 310oC, 85% solvent content and a 1:1 composition of H2O and ethanol; the bio-oil yields at those conditions was determined to be 40,6 wt%. The bio-oils were contained in the following order of prevalence, fatty acids, aliphatic hydrocarbons, N-containing compounds, O-containing compounds, aromatics and acid esters. Aliphatic hydrocarbons and fatty acids were the dominant functional groups. The following were the most abundant compounds in the 90 runs: heptadecane, pentadecane, eicosane, hexadecane 2,6,10,14-tetramethyl hexadecane and 9-octadecanoic acid.
Energy assessment and scheduling for energy optimisation of a hot dip galvanising process
(2021-12-01) Dewa, Mendon; Nleya, Bakhe; Dzwairo, Bloodless
The dearth of energy sustainability is posing major challenges both locally and glob- ally. Galvanising furnaces are categorised as dominant consumers of electricity in the overall galvanising industry. Relatively little research has been carried out concerning energy optimisation through sequencing or scheduling algorithms by way of enhancing the performance of galvanising lines. In this regard, the research centres on evaluating overall energy performance in this industry. The research sought to introduce an opti- mal energy optimisation-scheduling algorithm for a hot dip galvanising process. A DMAIC based methodology was presented for the provisioning of a structured prob- lem-solving process for improving energy efficiency in a galvanising process. Its framework embraces an energy sustainability assessment of four batch hot-dip galva- nising plants. Four energy minimisation opportunities were identified and quantifiable energy and cost savings, as well as avoided carbon dioxide emissions were derived from the analysis of one of the plants. Production or zinc used was identified as the main driver for electricity consumption for Plant 1, while the number of dips per month, amount of zinc used, and ambient temperature conditions were identified as the rele- vant variables for developing a regression model for Plant 2. The amount of zinc used and ambient temperature conditions were found to be the relevant variables for Plant 3. The derived regression model for Plant 4 was based on the amount of zinc used and ambient temperature conditions. The energy performance indicators for a galvanising plant were established through a comparison of actual and expected consumption, energy intensity index, cumulative sum, and specific energy consumption. A bi-objective GECOS algorithm was further introduced to reduce the total energy consumption as well as makespan. The simula- tion results revealed that the GECOS algorithm outperforms McNaughton’s algorithm, Shortest Processing Time Algorithm, and Integer Linear Programming algorithms on minimising makespan on parallel processing machines. The key contributions to the body of knowledge from the study include a unique eval- uation of electrical energy consumption by a hot-dip galvanising plant, development of an energy consumption baseline and performance indices, and the developed novel bi-objective GECOS algorithm that considers reducing total energy consumption by the process tanks as well as makespan. Future research work may focus on hybrid genetic algorithm-artificial immune system scheduling tools that would derive synergy from the advantages of both algorithms to improve energy performance.
Energy-efficient PLIA-RWA algorithms for transparent optical networks
(2017) Mutsvangwa, Andrew; Nleya, Bakhe
The tremendous growth in the volume of telecommunication traffic has undoubtedly triggered an unprecedented information revolution. The emergence of high-speed and bandwidth-hungry applications and services such as high-definition television (HDTV), the internet and online interactive media has forced the telecommunication industry to come up with ingenious and innovative ideas to match the challenges. With the coming of age of purposeful advances in Wavelength Division Multiplexing (WDM) technology, it is inherently practicany possible to deploy ultra-high speed all-optical networks to meet the ever-increasing demand for modern telecommunication services. All-optical networks are capable of transmitting data signals entirely in the optical domain from source to destination, and thus eliminate the incorporation of the often bulky and high-energy consuming optical to-electrical-to-optical (OEO) converters at intermediate nodes. Predictably, all-optical networks consume appreciably low energy as compared to their opaque and translucent counterparts. This low energy consumption results in lower carbon footprint of these networks, and thus a significant reduction in the greenhouse gases (GHGs) emission. In addition, transparent optical networks bring along other additional and favourable rewards such as high bit-rates and overall protocol transparency. Bearing in mind the aforementioned benefits of transparent optical networks, it is vital to point out that there are significant setbacks that accompany these otherwise glamourous rewards. Since OEO conversions are eliminated at intermediate nodes in all-optical networks, the quality of the transmitted signal from source to destination may be severely degraded mainly due to the cumulative effect of physical-layer impairments induced by the passage through the optical fibres and associated network components. It is therefore essential to come up with routing schemes that effectively take into consideration the signal degrading effects of physical -layer impairments so as to safeguard the integrity and health of transmitted signals, and eventually lower blocking probabilities. Furthermore, innovative approaches need to be put in place so as to strike a delicate balance between reduced energy consumption in transparent networks and the quality of transmitted signals. In addition, the incorporation of renewable energy sources in the powering of network devices appears to gain prominence in the design and operation of the next-generation optical networks. The work presented in this dissertation broadly focuses on physical-layer impairment aware routing and wavelength assignment algorithms (PLIA-RWA) that attempt to: (i) achieve a sufficiently high quality of transmission by lowering the blocking probability, and (ii) reduce the energy consumption in the optical networks. Our key contributions of this study may be summarized as follows: Design and development of a Q-factor estimation tool. Formulation, evaluation and validation of a QoT-based analytical model that computes blocking probabilities. Proposal and development of IA-RWA algorithms and comparison with established ones. Design and development of energy-efficient RWA schemes for dynamic optical networks.
Enhanced biohydrogen production from carbohydrate rich wastewater through anaerobic fermentation
(2020-11-30) Mutsvene, Boldwin; Chetty, Maggie; Pillai, S. K. K.; Bux, Faizal
In recent times,“the world has faced serious problems emanating from the use of fossil fuels which are detrimental to the environment at large. On the other hand, due to the industrial boom, many industries produce wastewater that is harmful to the environment hence, carbohydrate-rich industrial wastewater can be advantageously used to reduce impact on the environment. If subjected to anaerobic fermentation, organic wastewater has the potential to produce renewable energy sources that have less impact on the environment, including biohydrogen, which has little or no carbon footprint. While reducing the impact of the problems caused by the disposal of wastewater to the environment, the biological methods also offer a solution to the detrimental effects of fossil fuels and their after use effects. The study was mainly based on environmental protection and clean, renewable alternative energy production by generating biohydrogen from organic industrial wastewater as a substrate. Anaerobic digestion has been extensively studied, but dark fermentation, which is an emerging technology within anaerobic digestion that involves the production of hydrogen from carbohydrate-rich substrates, has less information documented regarding this technology. This technology is crucial in the because it forecasts beyond fossil fuel usage and is accompanied with long-term economic expansion and energy security as there are many reservations about fossil fuel reserves and their high risk of exploitation.” Biohydrogen potential tests (BHP) were performed on five different wastewater streams (yeast, alcohols, brewery, sugar, and dairy industries) to determine the stream with the best hydrogen potential. Rigorous characterisation of various wastewater streams was conducted; the main parameters of interest were COD, BOD, VS, TS, pH, among others. The BHP tests were conducted in triplicates in 600 mL Schott bottles charged independently with various wastewater streams and inoculated by the seed sludge from a local wastewater treatment plant at the different substrate to biomass ratios. The highest hydrogen composition was recorded with the brewery wastewater, which had 40.1% H2 in the off-gas as analysed by the gas chromatograph; and the minimum was found in alcohol wastewater, 21.4%. The Kepner-Tregor decision-making tool was conducted to determine the most suitable stream for the scaled-up reactor. A conclusion to use the brewery wastewater in the scaled-up Anaerobic Baffled Reactor (ABR) was reached. Four 10 L Anaerobic Baffled Reactors were used as the scaled-up reactors to optimise operating conditions for the production of biohydrogen using the brewery wastewater. Design-Expert software, under response surface methodology, was used to produce the matrix of combinations of the experimental runs by varying temperature (32-38℃), batch time (4-16 h), and pH (3.5-7.5); in total 20 runs were formulated.” The highest hydrogen production rate of 18.16 mL/h and the hydrogen yield of 30.98 mmol/gCOD were observed at temperature, batch time, and pH of 35℃, 4-10 h, and 5, respectively. The optimum operating conditions were determined to be a temperature of 36℃, batch time of 10.2 h, and a pH of 5.6. A predictive model, quadratic polynomial in nature, was developed after an intensive analysis of variance, a regression coefficient between predicted and actual hydrogen production rates was found to be 0.92. A system was run on optimum conditions to validate the developed mathematical model. The maximum hydrogen potential rate (HPR) determined in this study was 6.11% higher than the predicted value. The validation runs were also performed as control experiments for comparison between a system with nanoparticles and a system without nanoparticles with regards to the HPR. 25.37% H2 and 21.85% H2 were determined for with magnetite nanoparticle system and a system without nanoparticles, respectively. The experiments with nanoparticles garnered 44% higher HPR (23.41 mL/h) than a system without nanoparticles.
Evaluating the removal of emerging contaminants from the eThekwini Municipality REMIX Water Treatment Plant
(2024-05) Manyepa, Prince; Bux, Faizal; Seyam, Mahommed; Banoo, Ismail
The eThekwini Municipalities Department of Water and Sanitation (EWS) has initiated feasibility studies to determine whether it is financially and environmentally viable to implement direct potable water reuse (DPR) projects, and one of them is the REMIX Water Treatment Plant (RWTP) which is located within the Port of Durban and abstracts wastewater and sea water for treatment and potential future re-use. However, a review of the extant literature has highlighted that wastewater and seawater are primary sources and "sinks" for various contaminants of emerging concern (CEC). Emerging contaminants (ECs) can be endocrine-disrupting chemicals or cancercausing agents in humans and animals if they are constantly present in drinking water. This study evaluated the efficiency of the RWTP for the removal of different classes of pharmaceutical compounds by measuring the feed water and effluent of each treatment unit along the RWTP. The Quantitative structure-activity relationship (QSAR) model and OPBT criteria were used to screen these compounds for persistence, bioaccumulation, and toxicity (PBT) behaviour in the water matrix. This was done to produce a priority list that allowed effective monitoring of each treatment unit for observed PBT compounds that should not be present in reclaimed water intended for human consumption. The QSAR is a suitable alternative to the costly and labourintensive in vivo screening experiments in the water matrix. It works in tandem with the new animal rights regulations, is safer than laboratory experiments, and also saves time. The study found that 4 out of 20 compounds were identified as potential PBT compounds by consensus agreement in both methodologies. The goal of this study was to assess the removal of ECs prioritised using the QSARINS model and OPBT criteria by carrying out a human risk analysis for reclaimed water proposed for drinking purposes within the City of Durban. This informed decision-makers, plant managers, and operators on what to constantly monitor or add to the treatment plant for the safe production of drinking water. Excellent removal rates of ECs were observed in the membrane biological reactor (MBR) and the reverse osmosis systems (ROs). The removal rates in MBR and ROs ranged from 38% to 100% and 96%, respectively. Excellent removal rates for heavy metals and nutrients across the treatment technology were also achieved in the final product water. The calculated risk/hazard quotients (RQ) for all ECs and heavy metals were also conducted in the reclaimed REMIX water. An RQ/HQ > 1 meant a high risk of ECs or heavy metals, and <1 meant the risk was negligible. Except for some anomalies caused by ion suppression or matrix effects during the analysis, the majority of the ECs in the reclaimed water RQ were found to be less than 1. Identification of chemical, biological, and physical hazards using HACCP system principles led to the identification of critical control points for the technology. Five critical control points were examined, and techniques for successful RWTP monitoring were proposed based on the study findings.
Evaluation of Kaolinite and activated carbon performance for CO2 capture
(2021-03) Akpasi, Stephen Okiemute; Isa, Yusuf Makarﬁ
Global climate change is one of the major threats facing the world today and can be due to increased atmospheric concentrations of greenhouse gases (GHGs), such as carbon dioxide (CO2). There is also an immediate need to reduce CO2 emissions, and one of the potential solutions for reducing CO2 emissions is carbon capture and storage (CCS). This work investigated the performance assessment of kaolinite and activated carbon (AC) adsorbent for CO2 capture. In particular, the effect of operating parameters such as temperature, bed height, inlet gas flow rate etc. on CO2 adsorption behaviour of the adsorbents was also investigated. Extensive research on the development of adsorbents that can adsorb large amounts of CO2 with low energy consumption has recently been carried out. In CO2 adsorption technology, the challenge is to develop an adsorbent that is not only non-toxic, eco-friendly, and cost-effective, but also has the potential to extract CO2 gas from a mixed gas stream selectively and effectively. Due to the possibility of a potential adsorbent due to its low cost, rich natural abundance and high mechanical and chemical stability, this study proposes kaolinite. As the presence of clay minerals in soils serves as a pollutant collector to enhance the atmosphere, kaolinite has the potential to be an efficient adsorbent for CO2 capture. Kaolinite was investigated as an adsorbent in this research to confirm if it is suitable for CO2 capture. Kaolinite/activated carbon composite adsorbents were synthesized. Sugarcane bagasse was used in preparing the activated carbon (AC). ZnCl2 was impregnated onto sugarcane bagasse during the preparation of activated carbon (AC) to improve the physical properties (surface area, pore size and pore volume) and the CO2 adsorption capacity of the activated carbon (AC) adsorbent developed. The materials were characterized and tested for CO2 adsorption (activated carbon and kaolinite). BET, FTIR and SEM studies were used to classify the adsorbents for their surface area and pore properties, functional groups, and surface morphology, respectively. BET analysis was conducted and the pore volume, pore size and surface area of the adsorbent materials were reported. Functional groups were actively present in the adsorption process. This was verified using FTIR spectroscopy. The kaolinite adsorbent was not feasible for CO2 capture. BET, SEM, and custom-built CO2 adsorption equipment have confirmed this. In contrast to literature, the CO2 adsorption capacity of kaolinite was low. This is due to the fact that kaolinite used in this study is not suitable as adsorbent for CO2 capture as they exhibited a low CO2 adsorption capacity. The results obtained in this study show that temperature, bed height and inlet gas flow rate influenced the adsorption behaviour of activated carbon (AC), kaolinite and kaolinite/activated carbon composite adsorbent during CO2 capture. At 30 0C, activated carbon (AC) exhibited an adsorption capacity of 28.97 mg CO2/g, the highest capacity among all the adsorbents tested. Kaolinite-activated carbon composite adsorbent offered CO2 adsorption capacities of 18.54 mg CO2/g. Kaolinite provides the lowest capacity of 12.98 mg CO2/g. In conclusion, this research verified that CO2 adsorption with kaolinite and activated carbon is favoured at low temperatures, low operating CO2 flowrates and high column bed height.
Evaluation of water resource management systems in eThekwini Municipality
(2024-05) Faya, Nosipho Buhle; Anugwo, Iruka C.; Twala, Bhekisipho
Water is an essential and critical resource for human, animal and plant survival and our continuing existence on planet earth. Water is increasingly becoming a scarce resource, and the issue of water scarcity has been exacerbated in intensity by climate change, as well as aging water resource infrastructure in many countries; such as the republic of South Africa. This study aimed at evaluating the water resource management systems, in that is rooted in a qualitative research method and phenomenological paradigm. Thus, primary data were collected from personnel in high and strategic positions in the government entity, eThekwini Municipality Water and Sanitation. This qualitative data was then subjected to content analysis and themes. The study findings are based on the eThekwini region and its resiliency and adaptability to climate change. In order to achieve that, this study utilized an in-depth interview and semi-structured interview approach to garner respondents’ perceptions, opinions, expertise, judgement and experiences on issues of water resources management systems and infrastructure resiliency and adaptability to the impact of climate change in Durban. The data revealed that the current state of water resource infrastructure is not satisfactory, or resilient enough to withstand the impact of climate. The study findings also indicated the urgent need for the eThekwini municipality’s water resource infrastructure to be upgraded for optimal operation and for resiliency to environmental and technical challenges. The study further reveals that the eThekwini municipality is considering embarking on joint venture projects that would adopt the innovative concept of reusing, remixing and recycling treated wastewater, as well as the installation of desalination plants for effective water resources management. From our findings, we saw that eThekwini municipality needs to adopt new technologies that would enable integrated and adaptive, resilient components in their water resource management systems. The study recommended that eThekwini municipality should endeavour to strive towards upgrading the current state of its water resource infrastructure so that it is in a satisfactory state, and resilient enough to withstand impact of climate change.
Experimental and computational exploration of advanced biodiesel fuels and hybridisation process evaluation of feedstocks and their chemical combinations
(2022-09-29) Etim, Anietie Okon; Musonge, Paul; Eloka-Eboka, Andrew C.
To address the alarming crisis of global energy demand, environmental degradation and climate change, biomass derived diesel fuel is one of the superior renewable fuel options, considered as suitable alternative to petroleum fuel. Important fuel characteristics of biomass derived diesel fuel ranges from being recyclable available local fuel to auspicious performance in combustion emission reduction. In this study, waste oil and other indigenous tropical seed oils, which include; used sunflower oil (USO), linseed oil (LSO), marula seed oil (MSO), baobab seed oil (BSO) and Trichilia emetica kernel oil (TEKO) were investigated for biodiesel production and further scrutinised for the hybridization process for effective applications. The process of hybridization applied was a two-pathway approach via in-situ and ex-situ transesterification reactions. Biological wastes mineral-rich materials such as eggshells, banana peels and pawpaw peels were used to produce the bio-alkaline catalysts. The waste materials were washed with distilled water, dried in the oven and further subjected to high temperature of calcination in the furnace. Eggshells were calcined at 900 oC for 3 h while pawpaw and banana peel were calcined for 3 h at 700 oC respectively. The calcined ash of eggshells and banana peel, eggshells and pawpaw peels were bonded respectively via wet impregnation method and further activated at high temperatures to obtain hybridized bio-alkaline catalysts. The synthesized samples of all catalyst were characterized using Fourier transforms infrared (FT-IR), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The catalysts produced were applied in the production of biodiesel from waste and underutilized oils such as used sunflower oil (USO), linseed oil (LSO), marula seed oil (MSO), baobab seed oil (BSO) and Trichilia emetica kernel oil (TEKO) under an optimized transesterification reaction process. The operating parameters considered viz methanol-to-oil ratio, catalyst loading, and reaction time temperature were investigated and optimized using Response surface methodology (RSM) to obtain the best operation condition for the maximum yields. The optimized condition established from the biodiesel fuel produced was used as a standard for the transesterification reaction condition for the single and hybrid oils. The two pathways hybrid process; In-situ (co-mingling of oils prior transesterification) and Ex-situ (comingling of the single biodiesel fuels after transesterification) was used to evaluate and compare the differences between the two processes and how effective they can be deployed commercially. The four crude oils considered for the study (USO, LSO, MSO and BSO) were analysed while fractions of them were individually converted via transesterification to obtain single biodiesel fuels (SOBFs): used sunflower oil methyl ester (USOME), linseed oil methyl ester (LOME), marula oil methyl ester (MOME) and baobab oil methyl ester (BOME). Then the remaining fractions were pre-treated and co-mingled in 27 various combinations to form new oils (of bi-and poly-hybrids) called the hybridized oils (HOs). These different combinations were then trans-esterified to obtain hybridized oil methyl esters (HOMEs) - In-situ hybridization. Thereafter, the SOBFs - (USOME, LSOME, MSOME and BSOME) were hybridized in the same pattern following the same ratios to form new products termed hybridized methyl ester (HMEs) - Ex-situ hybridization. All the produced biodiesel fuels: USOME, TEKOME, LOME, MOME, BOME and HOMEs were individually blended with petrol-diesel and their chemo-physical properties were analysed and compared with the international (ASTM and EN) and South African (SANS) standards. The impact of the chemical combinations on the physico-chemical properties of all the biodiesel produced was investigated and computed using artificial neural networks (ANN). Their influence on the important thermophysical fuel properties such as cetane number and calorific values were also evaluated. The characterization results revealed that eggshell is an excellent source of natural CaO while the banana and pawpaw peels are rich in potassium compounds such as: KCl, K2SO4, K2CO3, K2O which are efficient catalyst compounds for biodiesel production. The hybridized catalysts were found to be effective and of high basicity and active in oil conversion to biodiesel. The process of in-situ and ex-situ hybridization and their blends with petro-diesel were found to be a very effective approach to be adopted in the biodiesel production process. High conversion of biodiesel yields was obtained via the process of in-situ transesterification, indicating that the transesterification process is not affected by the number of mixing ratios of oils. The two process pathways offered improved properties that are much more conformable to standards than most of the single biodiesel produced fuels. Some properties such as density, acid value, viscosity, calorific value and cetane number were found a bit lower in ex-situ than in in-situ hybrids under the same hybrid conditions. The predicted properties obtained from the two protocols by ANN show good alignment with the experimental values with high regression coefficients close to unity (1). The improved fuel properties obtained following these protocols were within the international and South African standard specifications. The general principles and model predictions of the subsequent properties of biodiesel presented in this study will serve as a database and template for effective development for the overall biofuels application
Exploiting recycled plastic waste as an alternative binder for materials used in the construction industry
(2024-05) Gounden, Kimendren; Mwangi, Festus Maina; Mohan, Turup Pandurangan; Kanny, Krishnan
The population in the world is growing at an alarming rate and four local and global threats viz. plastic pollution, high unemployment, inadequate housing for all citizens and damage to the ozone layer causing climate change continue to emerge. The overwhelming demand for plastic goods in daily use resulting in plastic waste pollution has become an environmental challenge. Plastic waste is now becoming extremely dangerous due to their rapid accumulation in the environment and in landfills, and their improper disposal methods leads to many harmful effects on land, air, marine life and humans. Incineration of plastic waste is already posing several health risks. Concurrently, the cement, building and construction industry is amongst the biggest contributor to carbon dioxide (CO2) gas emissions, which poses an added environmental challenge. This creates a negative image on the use of cement-based masonry as construction materials, which renders it unsustainable. Hence, an alternative construction material is required. The manufacture and utilisation of burnt clay bricks have become an area of debate which led to a move towards greater sustainability. Therefore, there is need for a strategy to reduce plastic pollution, create job opportunities, provide alternate ways of constructing affordable ecofriendly houses, and reduce the depletion of the ozone layer for the benefit of all citizens. This strategy is explored in this research study that supports, enhances and promotes sustainability. The efficacy of producing eco-friendly plastic-sand bricks as a feasible solution and an attractive alternative to cement or burnt clay bricks have been investigated in this study. This investigation encompasses an effort to combat issues related to plastic waste, high unemployment, rising building costs and climate change. In the first stage the study analyses the use of High-Density Polyethylene (HDPE) and river sand using six different ratios of sand(s): plastic(p) viz. 60s: 40p; 65s: 35p; 70s: 30p; 75s: 25p; 80s: 20p and 85s: 15p. The second stage consisted of the addition of 1%, 5% and 10% of Kaolin Clay DSF which was experimentally added to each of the different ratios of sand: plastic respectively to improve the mechanical and environmental properties towards producing eco-friendly plastic-sand bricks. The mechanical tests showed significant improvement. Results revealed that the addition of 5% Kaolin Clay DSF, significantly increased the compressive strength from 21.4 MPa to 52.76 MPa in the 75s:25p ratio, the modulus of elasticity from 1109.35 gigapascal (GPa) to 2434.84 GPa and the short beam strength from 1.84 MPa to 2.27 MPa. The addition of 10% Kaolin Clay DSF, significantly increased the results for the impact test from 4.6 joules to 5 joules in the 75s:25p ratio. However, the addition of 5% Kaolin Clay DSF revealed an increase from 4.6 joules in the same ratio to 4.7 joules. The hardness test revealed that the impression of the nail did not affect the samples which implied that the plastic-sand bricks are durable and tough in all six ratios. The environmental tests also showed significant improvement. Results revealed that the addition of 5% Kaolin Clay DSF decreased the rate of water absorption from day 1, being 0.78% to 0.43% on the 21 st day. The plastic-sand brick as a composite material is an electrical insulator. The plastic-sand brick sample resisted the immediate absorption of water with respect to 0%, 1%, 5%, and 10% addition of Kaolin Clay DSF. No visible deposit of alkali was present when the efflorescence test was done. The fire test revealed that the addition of 10% Kaolin Clay DSF with an increase in sand content drastically reduced the linear burning rate significantly in the 75s:25p ratios from 10.52 mm/min to 2.10 mm/min respectively. This decrease in approximately 81% in the burning rate is significant. The main conclusion of this research study is that HDPE plastics can be used to produce plasticsand bricks that are durable, significantly high in strength and eco-friendly as compared to the conventional cement or burnt clay bricks. The addition of Kaolin Clay DSF improves both the mechanical and environmental properties of the plastic-sand brick. The manufacturing of plastic-sand bricks is an eco-friendly process. Thus, recycled plastic waste can be effectively used as an alternative binder material in the construction industry.