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A study into homogeneously and heterogeneously catalysed transesterification of waste cooking oil for the production of biodiesel.
(2024) Rugnath, Keshav.; Mohammadi, Amir Hossein.
The ever-increasing population around the globe, along with the imbalances in food and fodder supply, the dwindling supply of fossil fuels, and the diminishing availability concerning natural resources have led to the emergence of significant energy challenges on a global scale. To address these issues, it is essential to pursue sustainably and economically viable growth, relying on domestic and renewable energy sources, to reduce the need for imported oil. An established renewable alternative to imported oil is biodiesel. For biodiesel to become market competitive with diesel, it is important to ensure the development of cost-effective processing schemes to optimize production. This research paper aims to determine whether heterogeneously and homogeneously transesterification of waste cooking oil can be used to produce biodiesel efficiently. The chosen homogeneous catalyst was Potassium Hydroxide,
and the heterogeneous catalyst was Magnesium Oxide. The selected feedstocks were waste canola oil and ethanol. After a pre-treatment process, the acid value of the waste cooking oil was calculated to be 0.1167 mg KOH/g, indicating that a single step transesterification process can be used. The box-Behnken Design was utilised on Minitab Statistical Software to generate 27 different experiments using variations in the process variables. The process variables considered in this study were Catalyst Loading, Reaction Temperature, Reaction Time, and
Alcohol to Oil Molar Ratio. The optimum yield for biodiesel produced from used canola oil utilising potassium hydroxide and magnesium oxide was 91.53% and 96.02%, respectively. From the various models explored, the full quadratic model most accurately fitted both experimental results with the KOH catalyst experimental data obtaining an R2 value of 0.9575 and the MgO catalyst experimental data obtaining an R2 value of 0.9710. Minitab calculated the optimal process variable conditions using the KOH catalyst to have a reaction temperature of 74 oC, a catalyst loading of 0.0673%, a total reaction time set at 84.55 minutes and an alcohol to oil molar ratio of 26:1. Minitab calculated the optimal process variable conditions using the MgO catalyst to have a reaction temperature at 54.41 oC, a catalyst loading of 1.44%, total reaction time set to be 120 minutes and alcohol to oil molar ratio to be 18.18:1. The kinematic viscosity was higher than the ASTM maximum limit of 6 mm2/s for both the pure KOH and MgO Biodiesel samples at 8.29 mm2/s and 15.24 mm2/s, respectively. It was concluded that further modification would be required for direct use in an engine. The research for this study found KOH to be the most suitable catalyst for transesterification of waste cooking oil.
This conclusion is drawn from the pure KOH biodiesel having a much lower viscosity than MgO biodiesel; KOH biodiesel also had a higher flash point than pure MgO biodiesel of 103.67 oC. The bio-jet fuel blends were not in accordance with many of the ASTM Standards. The acid values of the jet fuel blends (B10 and B20) from KOH and MgO samples were over the allowable limit set at 0.015 mg KOH/g oil. The pour point for Jet fuels should be approximately -47 oC. All the jet fuel blends (B10 and B20) exceeded the maximum limit. The critical success factors for biodiesel production in South Africa were determined.
Teachers’ experiences of teaching history using english as a language of teaching and learning in the intermediate phase.
(2023) Biyela, Rosemary Nokuthula.; Shoba, Makhosi.
The prime purpose of this study was to explore teachers’ experiences of teaching History using English as the language teaching and learning intermediate phase (Grades 4 -6). Six History teachers were purposely selected using convenience sampling and data was generated using a focus group and semi-structured interviews. Data was analysed using a thematic analysis. The conceptual Framework, Cultural Historical Activity Theory (CHAT), was also used to analyse teachers’ experiences. More so, ethical considerations and trustworthiness issues were adequately addressed during the study. The findings of the study indicate that History teachers’ experiences illuminated using innovative methods and traditional methods to teach complex History concepts. While the factors that influence teachers’ experiences were shortage of resources, code-switching, teachers’ knowledge, and language barrier. The findings of this study further revealed that teaching History using English language in rural schools has been a challenging experience for many teachers and learners in the townships’ schools. In it, the results demonstrate that the experiences of language barrier, lack of resources, and the need to follow the curriculum as prescribed by the department have been particularly detrimental for teachers and learners thereby affective the outcomes of teaching History. In conclusion, the study recommends teaching English across curriculum, and that History teachers must be both History and English specialists. Curriculum managers such as Departmental Head must be proactive and initiate development support group system within the schools.
Characterisation of faecal material waste from rural schools’ onsite sanitation systems for its safe disposal and optimal valorisation.
(2023) Ramruthan, Yuri.; Santiago, Septien Stringel.; Mercer, Edwina.
Poor sanitation facilities in South African rural schools are barricading youth from their education, due to an unsafe learning environment. Inadequate sanitation facilities in South African rural schools not only pose severe health risks but also hinder progress towards achieving the 4th and 6th Sustainable Development Goals (SDGs). This study aims to assess the optimal valorisation of faecal material derived from rural school sanitation systems, including ventilated improved pit latrines (VIPs), mobile toilets (MTs), and septic tanks (STs) in Durban, South Africa. Faecal material, defined as the combination of solid waste, urine, and other gastrointestinal excretions, underwent a thorough analysis of its physico-chemical, thermal, thermodynamic, and mechanical properties. Analytical tests for characterizing faecal material were conducted in line with standard methods utilized by the WASH R&D Centre and the Methods for Faecal Sludge Analysis by Velkushanova et al. (2021). The findings were used to formulate decision matrices for determining the most efficient treatment and emptying strategies based on the characteristics of the faecal material. Notably, all containment systems exhibited comparable energy and nutrient potential suitable for the production of fuels and fertilizers, respectively.Particularly, fresh faeces from MTs exhibited the highest solids concentration (~18% TS), organic fraction (~78.37%) Volatile Solids, and calorific value (23.24 MJ/kg dry solids). The opposite was observed for VIPs (~45.47% VS, ~8.5% TS) with a calorific value of (18.4 MJ/kg dry solids). MTs illustrated the highest mean nutrient composition and improved treatability - a lower shear yield stress at the same solid’s concentration to the more degraded faecal sludge from VIPs and STs. This inadvertently improved flowability and reduced the pump head requirement for emptying technologies and treatment processes.. Ultimately faeces from MTs were considered to have high strength. VIPs demonstrated the highest TSS, TDS and lowest SVI at 3,6 g/L, 1422 mg/L and 75 ml/g respectively. Together faecal material from all On Site Sanitation systems, exhibited a water activity of ~1, suggesting good dewaterability potential, with results signifying the moisture in the sludge is unbound, so less difficult to remove. Particle size for school toilets ranged between 0,7- 2046,7 μm 0,6 -1202,3 μm and 0,7-1492,5 μm for VIPs, MTs, and STs, respectively. Thermal conductivity for each OSS (MTs, VIPs, STs) represented a narrow range for faecal sludge and faeces ranging between 0,48-0,59 (W/K/m), which were in close approximation to the thermal conductivity of water.
Overall, this study guides engineers and regulators in establishing safe, equitable and sustainable rural school sanitation systems, by promoting resource recovery options such as biochar, fertilizers, and biogas. High strength faecal material from MTs offered the greatest potential for resource recovery, however, requires multiple treatment stages to ensure safe environmental discharge standards are met. They also act as a temporary containment solution, with limited maintenance and negative user perception. The large presence of trash, high TS% and denser faecal material within MTs rendered it most applicable to manual emptying methods (MAPET and manual diaphragm). Consequently, the preferable direction for advancing rural school sanitation, is the adoption of water-borne systems where possible. A transition towards these systems will minimize the spread of diseases associated with non-flush systems (MTs and VIPs). Additionally, it will enhance the overall comfort of female students using school toilets, subsequently reducing the fatalities that have occurred from children drowning in pit latrines. Water-borne sanitation systems, such as STs better facilitate the use mechanical emptying methods, providing a wider array of mechanical emptying options. Furthermore, STs demonstrated viable treatment options owing to its better stabilized waste, like composting and vermicomposting. Moreover, progressive options for areas with no water access, include, contained-based sanitation or
re-invented toilets such as composting toilets. This will allow for faeces to be valorised relatively fresh, obtaining direct resource recovery, for high quality end-use products like biogas, and biochar for a fuel source.
Production of high-value Dissolving Wood Pulp (DWP) from sawdust waste.
(2023) Balkissoon, Simiksha.; Sithole, Bishop Bruce.; Andrew, Jerome Edward.
This study adopts a circular economy framework, aiming to divert waste from landfills and channel it towards more lucrative value chains. A novel approach for producing dissolving wood pulp from wood sawdust waste, focusing on three sawdust species: hardwood, softwood, and a mixture of hardwood species was undertaken. The two-step low-temperature chemical process (60-80℃) involved delignification using ammonium persulphate and subsequent bleaching to remove residual lignin, and hemicellulose, and enhance pulp brightness. This approach provides a more environmentally friendly alternative with reduced chemical, water, and energy intensity compared to complex traditional processes involving several stages.
The delignification process was optimised on a benchtop level for reaction time, chemical concentrations, liquid-to-wood ratios, and temperature following respective benchtop bleaching treatments. The resulting bleached sawdust pulp, with yields ranging from 38-46% and an ISO brightness of 86-88%, proved unsuitable for viscose production due to the low intrinsic viscosity (180-310 ml/g). However, microcrystalline cellulose production remained viable requiring a final acid hydrolysis step to modify the degree of polymerization. Scaling up to a pilot-scale operation, the study included characterisation of the final microcrystalline cellulose using various analytical techniques such as wet chemistry, thermogravimetric analysis, microscopic and spectroscopic techniques, chromatographic and mass spectrometry methods, particle size analysis and colourimetric methods of analysis. Characterization using these methods showed some close similarities between the prepared microcrystalline cellulose samples and commercially available microcrystalline cellulose.
Microcrystalline cellulose yields varied between 30-42%, the degree of polymerisation ranged between 257-398, brightness ranged between 79-86%, pH between 5-7 and the crystallinity index between 76-84%, with physical attributes like particle size requiring further modification for commercial applications. By-product recovery explored the potential of ammonium sulphate, benefiting both agricultural and non-agricultural applications. A techno-economic assessment, incorporating recovery methods, indicated a return on revenue of 78-84%, an internal rate of return of 67-70%, and a payback period of 1-2 years, with marginal effects from acid (hydrochloric) recovery.
The study highlighted the highest potential in microcrystalline cellulose derived from hardwood, with bleached softwood sawdust showing promise for lyocell production due to its high degree of polymerization. Overall, the methodology not only demonstrated environmental benefits but also economic viability, making it a promising avenue for sustainable wood waste utilization.
Developing a framework for the growing and commercialisation of Stevia in Kenya.
(2025) Zulu, Thandi Jane.; Kanyangale, MacDonald.; Nzimakwe, Thokozani Ian.
While there is great potential for the commercialisation of Stevia, small and medium enterprises in many countries, including Kenya, are not clear on the cultivation and process of bringing new products, services, or innovations to the market with the goal of generating sustained revenue. The aim of this qualitative study was to explore and develop a framework for the commercialisation of Stevia in Kenya. The critical questions in this study were the crucial factors influencing Stevia's commercial viability and how farmers surmounted these to achieve sustainable development. The qualitative study involved ten experienced Kenyan Stevia farmers (six females, four males) selected using purposive sampling in Nyeri, Nakuru, and Thika. Data were collected from ten experienced Kenyan Stevia farmers using semi-structured interviews using an interview guide to get an in-depth understanding of the commercialisation of Stevia. The collected interview data were analysed using thematic analysis to reveal key themes related to Stevia commercialisation. The themes in this study reveal a complex interplay of opportunities, such as increased revenue and job creation, against challenges like high costs, financial barriers, and environmental risks. The success of Stevia farming depends on access to quality seedlings, water, and modern farming technology. While demand grows and sustainable practices are encouraged, industry growth faces limitations due to inadequate infrastructure and land availability. This study revealed that providing financial and market-readiness support to Stevia farmers is essential. The study underscores the necessity of specific financial support, the impact of environmental and technological progress on yields, and management's critical role in upholding quality. Collaboration, dedication to sustainability, and forward-thinking are critical for the success of the Stevia industry. The study has contributed a comprehensive Stevia value chain framework for the Stevia sector in Kenya, highlighting the critical role of government support, market access, and sustainable practices. It emphasises the importance of a multifaceted approach, integrating financial aid, technological advancements, and market expansion to bolster the industry's growth. The findings advocate for strategic interventions to strengthen the Stevia supply chain, which could catalyse economic progress and food security within the region. This research serves as a cornerstone for policy formulation, offering a blueprint for sustainable agricultural development and reinforcing the significance of empowering Stevia farmers in the global market.