M. Tech. (Department of Chemical Engineering, Faculty of Engineering and Technology), Vaal University of Technology. / This study presents the use of sodium methoxide as a homogeneous catalyst and impregnated Perlite (potassium hydroxide/perlite) as heterogeneous catalyst for production of biodiesel using Baobab and Marula oil respectively. One factor at a time experimental design was used to study the effect of temperature, time, amount of catalyst and methanol to oil ratio on the transesterification of baobab oil using sodium methoxide as a catalyst. Response surface methodology was used to study the effect of temperature, time, amount of catalyst and methanol to oil ratio on the transesterification of marula oil using perlite as a catalyst. Biodiesel yield produced using sodium methoxide and baobab oil was 96% at 1 hr reaction time, 30 wt.% methanol to oil ratio, 1 gram of catalyst and 60°C reaction conditions. Biodiesel yield produced using perlite and marula oil was 91.38% at 3.55 hr reaction time, 29.86 wt.% methanol to oil ratio, 3.46 grams of catalyst and 70.41°C reaction conditions. Perlite catalyst was reusable for transesterification of marula oil while sodium methoxide was not reusable for transesterification of baobab oil. Baobab and Marula biodiesel fuel properties are comparable to American Society for Testing Materials standard (ASTM).

In a fast-moving world with high demand for deliveries of various goods, the need for high performing transportation systems and networks has grown rapidly. As a reaction, the number of trucks has increased, which together with other transport solutions to cover the need has caused a growth of CO2e emissions. Sustainability awareness has pushed companies to consider and implement more sustainable transportation solutions to reduce the environmental impact from transport. The purpose of this study is to analyze and identify the root causes of CO2e emissions in a transport, delivery network. An understanding of the common characteristics of transports causing the highest levels of emissions is provided with an analysis of distances, modalities and fuel types. Additionally, alternatives are simulated to compare the current network to a system with different solutions implemented. The study was performed by analyzing available literature of intermodal transportation systems, alternative fuel types and different modalities. Data for a full year was collected from Scania AB, cleaned and analyzed to identify the type of transport to study further. The characteristics were identified by forming geographical regions based on location and available infrastructure, divide the transports by legs and distances, and sort the transports by fuel types and modalities. As a result, several flows were identified as examples representing the network where the effects of making changes could be most accurately identified.Simulations were performed for exemplary flows providing results for four out of seven regions in the network. Available infrastructure for different modalities was considered for each region and alternative fuel types researched. Considering the possibilities within the regions, each flow was simulated with the available solutions in the region. Additionally, infrastructure potentially developing in the near future, was considered as an alternative in cases where current availability is limited.The results from the simulations were unambiguous for intermodal transportation systems in the cases where electric rail was utilized over any mean of truck transport, regardless of the fuel type. Road transports run on Diesel were used as the baseline for the simulations as it is the highest utilized fuel type. Simulations of road transports on alternative fuels also provided a positive result for CO2e emissions as they decreased in all cases. / I en snabbföränderlig omvärld med en hög efterfrågan av olika varor har behovet av högpresternade transportsystem ökat drastiskt. Som en reaktion på detta har antalet lastbilar ökat signifikant vilket i sin tur, tillsammans med andra transportlösningar som ska täcka det växande behovet, har lett till ökande CO2-utsläpp. En ökad medvetenhet inom hållbarhet har tvingat företag att överväga och implementera mer hållbara transportlösningar för att minska miljöpåverkan inom transport. Syftet med denna studie är att analysera och identifiera grundläggande orsaker för CO2-utsläpp inom ett transport- och leveransnätverk.En förståelse för de gemensamma egenskaperna inom transport som orsakar de högsta nivåerna av utsläpp anges genom en analys av avstånd, modaliteter och typ av bränsle. Dessutom är alternativa lösningar simulerade för att jämföra det nuvarande nätverket mot ett system med andra implementationer.Studien genomfördes genom att analysera tillgänglig litteratur om intermodala transportsystem, alternativa sorter av bränsle och olika modaliteter. Data för ett helt år samlades in från Scania AB, rensades och analyserades för att identifiera vilken form av transport som skulle studeras vidare. Egenskaperna identifierades genom att bilda geografiska regioner utifrån läge och tillgänglig infrastruktur, uppdelade i längre och kortare sträckor, samt genom att sortera transporterna efter bränsletyp och modaliteter. Som ett resultat identifierades en grupp av flöden som exempel, vilka representerade nätverket och där effekterna av att göra förändringar kunde anses mest exakta. Simuleringar för exempelflöden utfördes och gav resultat till fyra av sju regioner inom nätverket. Tillgänglig infrastruktur för olika modaliteter övervägdes för varje region och olika bränsletyper undersöktes. Med tanke på de olika möjligheterna inom regionen simulerades varje flöde med de tillgängliga lösningarna i regionen. Dessutom ansågs infrastruktur som skulle kunna utvecklas inom snar framtid som ett alternativ i fall där nuvarande tillgänglighet är begränsad. Resultaten från simuleringarna var entydiga för intermodala transportsystem i fall där elektrisk järnväg användes i stället för lastbilstransport, oberoende av bränsletyp. Vägtransport som drivs med diesel användes som referens för simuleringarna eftersom det är den mest använda typen av bränsle. Simuleringar av vägtransport på alternativa bränsletyper gav också positiva resultat för CO2-utsläpp som minskade i samtliga fall.

Increased amounts of available biomass residues from agricultural food production are present widely around the globe. These biomass residues can find essential applications as bioenergy feedstock and precursors to produce value-added materials. This study assessed the production of biogenic silica (SiO2) from different biomass residues in Africa, including cornhusk, corncob, yam peelings, cassava peelings and coconut husks. Two processes were performed to synthesize the biogenic silica. First, the biomass fuels were chemically pre-treated with 1 and 5% w/v citric acid solutions. In the second stage, combustion at 600 °C for 2 h in a muffle oven was applied. The characterization of the untreated biomasses was conducted using Inductively coupled plasma—optical emission spectrometry (ICP-OES), thermal analysis (TG-DTA) and Fourier-transform infrared spectroscopy (FTIR). The resulting ashes from the combustion step were subjected to ICP, nitrogen physisorption, Energy dispersive X-ray spectroscopy (EDX) as well as X-ray diffraction (XRD). ICP results revealed that the SiO2 content in the ashes varies between 42.2 to 81.5 wt.% db and 53.4 to 90.8 wt.% db after acidic pre-treatment with 1 and 5 w/v% acid, respectively. The relative reductions of K2O by the citric acid in yam peel was the lowest (79 wt.% db) in comparison to 92, 97, 98 and 97 wt.% db calculated for corncob, cassava peel, coconut husk and cornhusk, respectively. XRD analysis revealed dominant crystalline phases of arcanite (K2SO4), sylvite (KCl) and calcite (CaCO3) in ashes of the biomass fuels pre-treated with 1 w/v% citric acid due to potassium and calcium ions present. In comparison, the 5 w/v% citric acid pre-treatment produced amorphous, biogenic silica with specific surface areas of up to 91 m2/g and pore volumes up to 0.21 cm3/g. The examined biomass residues are common wastes from food production in Africa without competition in usage with focus application. Our studies have highlighted a significant end-value to these wastes by the extraction of high quality, amorphous silica, which can be considered in applications such as catalyst support, construction material, concrete and backing material.

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The road freight transport industry is facing radical changes that have the potential to fundamentally change the industry and pressure actors to embrace sustainability throughout their operations and implement technology in the broadest sense. The road transport industry is permeated by the use of fossil fuels and accounts for a significant part of the total CO2 emissions in the world. The entire industry is facing a fossil-free transition to reach the global environmental initiatives that countries have undertaken. At the same time as the industry is phasing out fossil fuels and using more sustainable fuels, the literature has a coherent view that transported goods are expected to increase significantly, and the imprint of the COVID-19 pandemic is increasingly affecting the industry with shortages of drivers and more vulnerable supply chains. This study has aimed to identify changes that affect the road freight transport industry in the short term (0-5 years) and the long term (5-20 years) with a focus on Europe. Furthermore, the study has applied the results of the study to a framework of future scenarios that previous research has contributed with, in collaboration with over 50 industry experts from the transport industry, to evaluate the impact of the changes concerning the expected futures that the research has resulted in. The study has applied literature search, a document study, and interviews with actors from the industry to collect relevant data and has resulted in most of the identified changes that the road transport industry is expected to be affected by in the short and long term.  The changes have been divided into three levels: ecosystem, business, and technology. The macro factors that affect the industry are increased regionalization and urbanization, increased customer requirements and consumption, and extensive introduction of laws and regulations concerning environmental impact and technology. Furthermore, the business changes are increased operational costs, the establishment of partnerships and alliances, circularity, and lack of staff. The technical factors consist of AI, IoT, and new more sustainable fuels. The primary effects include increased local production of goods that contribute to shorter transport distances but more transport, fossil-free transport with mainly electricity and hydrogen as fuel and thus new establishments of electricity and hydrogen infrastructure, many global initiatives to achieve sustainability, extensive application of technologies to streamline supply chains as well as more comprehensive rules and requirements regarding new unexplored technologies. Furthermore, future scenarios have been applied to evaluate the possible impact on the industry, which is visualized in figure 14. Suggestions for further research in the field are changes in the industry that take place but which this work has not addressed as it is not perceived as having significant effects on the road transport industry, such as increased deliveries of fresh goods, 3D printing, multimodal transport, and an older population and thus increased shipments of medical devices. / Vägtransportbranschen står inför radikala förändringar med potential att förändra industrin fundamentalt och pressar aktörerna till att anamma hållbarhet genomgående i sina operationer och implementera teknologi i vid bemärkelse. Vägtransportbranschen genomsyras av användning av fossila bränslen och står för en väsentlig del av de totala CO2 utsläppen i världen. Hela industrin står inför en fossilfri omställning för att nå upp till de globala initiativen som länder åtagit sig att genomföra i ett försök att bromsa den negativa klimatpåverkan som utsläpp leder till. Samtidigt som branschen ska fasa ut fossila bränslen och använda hållbarare drivmedel påstår litteraturen att transporterat gods ökar markant och COVID-19 pandemins avtryck påverkar i allt större utsträckning med brist på chaufförer och sårbarare försörjningskedjor. Denna studie har syftat till att identifiera förändringar som påverkar vägtransportindustrin på kort sikt (0–5 år) samt på lång sikt (5–20 år) med fokus på Europa. Vidare har studien tillämpat resultaten på ett ramverk av framtida scenarion som tidigare forskning bidragit med i samarbete med över 50 industriexperter för att utvärdera förändringarnas påverkan med avseende på de möjliga framtiderna som forskningen resulterat i. Studien har tillämpat litteratursökning, dokumentstudie samt intervjuer med aktörer från vägtransportindustrin i syfte att samla relevant data och har resulterat i flertalet identifierade förändringar som vägtransportbranschen förväntas påverkas av på kort och lång sikt.  Förändringarna har uppdelats i tre nivåer; ekosystemets, affärsmässiga samt tekniska. De makrofaktorer som påverkar industrin är ökad regionalisering och urbanisering, ökade kundkrav och konsumtion samt införande av lagar och regler. Vidare är de affärsmässiga förändringarna etableringar av partnerskap och allianser, cirkularitet och brist på personal. De tekniska faktorerna består av AI, IoT och nya hållbarare drivmedel. De primära effekterna innefattar ökad lokal tillverkning av varor som bidrar till kortare transportsträckor men fler transporter, fossilfria transporter med främst elektricitet och vätgas som drivmedel och därmed nyetableringar av el- och vätgasinfrastruktur, många globala initiativ för att uppnå hållbarhet, omfattande tillämpning av teknologier för att effektivisera försörjningskedjorna samt mer omfattande regler och krav gällande nya outforskade teknologier. Vidare så har framtida scenarios tillämpats för att utvärdera möjlig påverkan på industrin, detta är visualiserat i figur 14. Förslag på fortsatt forskning inom området är förändringar i industrin som sker men som detta arbete inte behandlat då det inte uppfattats som att de ger väsentliga effekter på vägtransportbranschen, exempelvis ökade leveranser av färska varor, 3D-printing, multimodala transporter samt en äldre befolkning och därmed ökade transporter av medicinska hjälpmedel.

Thesis Ph.D. ((Applied Mathematics)) -- University of Limpopo, 2022 / The world is under threat from the devastating effects of the continued depletion of the Ozone layer. Increased global warming is causing catastrophic ecological damage and imbalance due to accelerated melting of glaciers, rampant runaway veld res, widespread floods and other extreme events. The delegates to the Cop26 Climate Change Summit were reminded that the continued burning of fossil fuels is releasing carbon into the atmosphere at an unprecedented pace and scale and that the world is already in trouble. Complete substitution of fossil fuels with clean energy sources is the only solution through which the world can be saved from the deleterious effects of global warming. However, total dependence on renewable energy sources can only be possible through novel technology that enables efficient energy utilization and conservation. For instance, the evolution of advanced techniques in manufacturing processes has led to the reduction in the size of various industrial and engineering designs that consume reduced amounts of energy. Efficient energy utilization in thermo-fluid flow systems can be achieved through entropy generation minimization. Entropy is a thermodynamic quantity that represents the unavailability of a system's thermal energy for conversion into mechanical work. In this study, thermodynamic analysis of reactive variable properties third-grade fluid flow in channels with varied geometries and subjected to different physical effects was investigated with the second law of thermodynamics as the area of focus. Entropy generation and inherent irreversibility analysis were the main focus of the study where the sensitivities of these quantities to the embedded parameters were numerically and graphically described and analysed. The semi-analytic Adomian decomposition method, the semi-implicit fi nite difference scheme and the spectral quasilinearisation method were employed to solve the nonlinear differential equations modelling the flow systems. The results reveal that the effects of the parameters on flow velocity, fluid temperature, entropy generation and inherent irreversibility cannot be neglected. In particular, conditions for entropy generation minimization were successfully established and documented. / University of Limpopo

The goal of this study is to determine the economic implications of incorporating intermittent renewable energy into current power systems. The study also considers how to achieve an optimal mix of generating assets with renewable power, as well as the costs and advantages of using renewable energy sources to reduce CO2 emissions. Furthermore, this study examines how renewable energy exacerbates the "missing money" problem, which is a critical problem in electricity market design. The last part of this research is devoted to the calibration of the hybrid electricity grid model. We adopt positive mathematical programming (PMP) to calibrate the quadratic cost function for fossil fuel power plants. The calibrated model enables us to better analyze the impact of renewable energy on the electricity market. We find that due to the intermittency of wind and solar power, renewable energy could replace part of the peak load capacity like gas turbines but is not able to replace most of the base load capacity like coal capacities. The unintended consequences are that to eliminate the coal base load capacity, other forms of baseload capacities such as nuclear or hydropower capacity are necessary to incorporate the intermittent renewable power. Moreover, the capacity factors of remained peak load capacities and newly built base load capacities declined. Further support policies for maintaining the capacity adequacy standard are necessary for a reliable hybrid electricity market. / Graduate / 2023-09-26