No description available.

Thesis (M.U.R.P. 1979) from the Department of Architecture, University of Adelaide. / Includes bibliographical references (p. 165-188).

>Magister Scientiae - MSc / Energy production from coal comes with an environmental cost because of the toxic waste produced during coal combustion such as coal ash and brine which are potential water and soil pollutants. Coal ash and brine contain toxic elements which can leach and contaminate soils and ground water if not properly disposed. This study investigated the mobility of species in coal fly ash co-disposed with brine at Sasol Secunda power station in order to establish if the ash dam could act as a salt sink. The ash was dumped as a slurry with 5:1 brine/ash ratio and the dam was in operation for 20 years. It was hypothesized that the disposed Secunda fly ash was capable of leaching toxic metal elements into the surrounding soils and ground water and therefore could not be used as a long term sustainable salt sink. Weathered fly ash samples were collected along a 51 m depth core at the Secunda ash dam by drilling and sampling the ash at 1.5 m depth intervals. A fresh fly ash sample was collected from the hoppers in the ash collection system at the power station. Characterization of both Secunda fresh ash and Secunda weathered ash core samples was done using X-ray diffraction (XRD) for mineralogy, X-ray fluorescence (XRF) for chemical composition and scanning electron microscopy (SEM) for morphology. Analysis of extracted pore water and moisture content determination of Secunda fresh ash and Secunda weathered ash core samples was done in order to evaluate the physico-chemical properties of the fly ash. The chemical partitioning and mobility of metal species in the ash dam was evaluated using the sequential extraction procedure. The XRD spectra revealed quartz, mullite and calcite as the dominant mineral phases in the weathered Secunda ash core samples while Secunda fresh ash contained quartz, mullite and lime. The major oxides identified by XRF analysis for both Secunda fresh ash and Secunda weathered ash include: SiO₂, Al₂O₃, CaO, Fe₂O₃, MgO, Na₂O, TiO₂ and K₂O. The minor oxides identified for both Secunda fresh ash and Secunda weathered ash were P₂O₅, SO₃ and MnO. The trace elements identified for both Secunda fresh ash and Secunda weathered ash were As, Ba, Ce, Co, Nb, Ni, Pb, Rb, Sr, V, Y, Zr and Th. However, U was detected in some of the Secunda weathered ash samples but not in Secunda fresh ash. Both Secunda fresh ash and Secunda weathered ash was classified as class F based on the sum of the oxides of silicon, aluminium and iron by mass and the CaO content as reported by XRF analysis, and further classified as sialic and ferrocalsialic type highlighting the significant levels of Si, Al, Ca and Fe in the fly ash based on XRF analysis. The XRF analysis further showed that brine codisposal on the ash may have been responsible for the slight enrichment of some species such as Na, SO₄²⁻, Mg, K and V in the disposed Secunda weathered fly ash. However, there was no significant accumulation of these species in the disposed fly ash despite continuous addition of an estimated 117.65 billion litres of brine over the 20 year period that the dam existed. Furthermore, Secunda ash dam showed an overall total salt capture capacity of only -0.01 weight %, a strong indication that the ash dam was incapable of holding salts and would release elements to the environment over time. The scanning electron microscopy (SEM) analysis revealed spherical particles with smooth outer surfaces for Secunda fresh ash while Secunda ash core samples consisted of agglomerated, irregular particles appearing to be encrusted, etched and corroded showing that weathering and leaching had occurred in the ash dam. A decrease in pH, electrical conductivity (EC) and total dissolved solids (TDS) was observed in Secunda ash core samples compared to Secunda fresh ash. While Secunda fresh ash (n = 3) had a pH of 12.38 ± 0.15, EC value of 4.98 ± 0.03 mS/cm and TDS value of 2.68 ± 0.03 g/L, the pH of Secunda ash core (n = 35) was 10.04 ± 0.50, the EC value was 1.08 ± 0.14 mS/cm and the TDS value was 0.64 ± 0.08 g/L. The lower pH in the ash dam created an environment conducive to the release of species through leaching, while the lower EC and TDS in the ash dam implied the loss of ionic species from the ash which resulted from leaching. The moisture content (MC) analysis indicated that Secunda ash dam was very damp with an average MC of 54.2 ± 12.66 % for Secunda ash core creating favourable conditions for leaching of species in the ash dam while Secunda fresh ash had MC of 1.8 ± 0.11 %. The bottom of Secunda ash dam appeared water logged which could cause slumping of the dam. The sequential extraction procedure revealed that the major and trace elements contained in both Secunda fresh fly ash and Secunda weathered fly ash could leach upon exposure to different environmental conditions. The elements showed partitioning between five geochemical phases i.e. water soluble fraction, exchangeable fraction, carbonate fraction, Fe & Mn fraction and residual fraction. The labile phases consisted of the water soluble fraction, exchangeable fraction and carbonate fraction. The % leached out in the labile phases was expressed as a fraction of each element‟s total content e.g. Si (6.15 %) meant that 6.15 % of the total amount of Si in the ash was released in the labile phases. Na was the most labile among the major elements in the ash dam while Si and Al which form the major aluminosilicate ash matrix also showed significant lability. The % leached out in the labile phases for these major elements was as follows: for Secunda fresh ash: Si (6.15 %), Al (7.84 %), Na (11.31 %); for weathered Secunda ash core samples (n = 35): Si (7.53 %), Al (8.12 %), Na (11.63 %). This study showed that the fly ash generated at Sasol Secunda power station could not be used as a long term sustainable salt sink. The wet disposal method used at Sasol Secunda power station poses a high risk of groundwater contamination due to the high liquid to solid ratio used to transport the ash for disposal, which may lead to rapid dissolution of all the soluble components in the fly ash. The large volumes of brine that pass through Secunda ash dam in the wet ash handling system present a greater environmental concern than the dry ash handling system which involves small amounts of brine entering the ash dump.

>Magister Scientiae - MSc / Second generation biofuels production requires a suite of lignocellulolytic enzymes, acting synergistically to liberate the fermentable monosaccharides contained within agricultural waste materials. The use of thermostable lignocellulosic enzymes in a high-temperature process represents a number of advantages over their respective mesophilic counterparts, including increased solubility of the polymeric lignocellulosic substrates, enhanced enzyme processivity and reduced risk of bacterial and/or phage contamination during fermentation (Turner et al., 2007; Viikari et al., 2007). Alpha-L-arabinofuranosidases (AFases) participate in the deconstruction of lignocellulosic materials by hydrolysing the arabinofuranosyl bonds contained within the hemicellulosic portion of lignocellulose. In this study, three AFases isolated from compost-derived metagenomic DNA were characterised. Three genes derived from the fosmid metagenomic library constructed from 70°C compost were cloned into the pET21a(+) expression vector and expressed in E. coli BL21. The heterologously expressed proteins, AFase_H4, AFase_E3 and AFase_D3, were subsequently purified and their biochemical characteristics determined. All three AFases were shown to be active between pH 4.0 and 6.0. AFase_H4 and AFase_E3 displayed the highest activity at 60oC, while AFase_D3 had an optimum temperature at 25oC. Furthermore, the three AFases had differing thermostability profiles. In particular, AFase_E3 maintains 100% residual activity following 60 min incubation at 80oC and 24 hour incubation at 60oC. All three AFases have activity upon p-Nitrophenyl-arabinofuranoside and none against a range of alternative p-Nitrophenylglycosidic substrates. Phylogenetic analysis of the catalytic domain, identified within the amino acid sequences of the AFases, suggests that these AFases belong to glycoside hydrolase (GH) family 51. The difference in the AFase primary amino acid sequence motifs were used to infer differences in thermostability. All three AFases indicated similar biochemical and biophysical characteristics. AFase_E3 was determined to be the most thermostable amongst all three AFases. In the assessment of the three AFases respective suitability for inclusion in thermogenic bioethanol production processes, AFase_E3 was concluded as a suitable candidate for hydrolysis and synergistic testing on natural substrates. AFase_D3 possess the potential to be included in novel mesophilic industrialized process.

The diploma thesis focuses on world oil supply and aims to distinguish symptoms undoubtedly pointing to a possibly upcoming era of altered consumption and extraction patterns of oil products, which will be launched by "peak oil" -- a point when oil production reaches its maximum continues to decline. The thesis' objective is to analyse the probability of peak oil occurring and possible implications for world economy and selected countries. If proven true, it provides a an answer to the question whether the world economy can survive peaking without repercussions or whether it will shrink and decline into crisis. The first part defines the supply of oil and -- it's an overview of conventional and unconventional types of oil, petroleum products, oil fields, extraction techniques, energy effectiveness and substitutes. Furthermore, it defines "peak oil", it clarifies its history, strives to determine its possible date and compares it with the current oil situation. The second part surveys general implications of peak oil for world economics and politics -- it observes an unsatisfied oil demand, impact on the outputs of economies and the role of oil in economic crises. The political part follows with possible changes in the field of international politics. Lastly it tries to determine the effect on American suburbia. The third and final part is dedicated to selected countries, which are either important exporters or importers.

Thesis (M. Sc. (Microbiology)) --University of Limpopo, 2017 / The recent oil crisis and environmental concerns over fossil fuels has led to the development of biofuels from lignocellulosic materials. Two main sugars from lignocellulose that can be used for bioethanol production are glucose and xylose. Xylose is problematic, because there are few yeasts that can utilise and ferment it. Xylose fermentation is not as efficient compared to glucose fermentation. Some of the factors that affect xylose fermentation include rate of xylose consumption, aeration, temperature and inhibitors. To improve ethanol production and fermentations and to make the process economically viable at industrial scale, there is a need to find a robust microorganism that can ferment efficiently in harsh industrial conditions. Therefore, the aim of this study was to investigate by means of evolutionary engineering (adaptation), the adaptability of seven locally isolated yeasts in terms of growth on high xylose concentration, in the presence of acetic acid as well as at elevated temperatures. Seven yeast strains (Candida guilliermondii MBI2, Candida sp. Kp6.2ey, Candida tropicalis Kp21ey, Candida tropicalis Kp42ey, Candida tropicalis Kp43ey, Ogatea methanolica Kp2ey and Pichia kudriavzevii Kp34ey) were adapted to ferment 60 g/L xylose as sole carbon source in the presence of 3 g/L acetic acid at 37°C. P. kudriavzevii Kp34ey was the only yeast to adapt to these conditions. The adapted P. kudriavzevii Kp34ey was compared with the parental strain (unadapted) and a reference strain, Scheffersomyces stipitis NRRLY-7124, using different volumetric oxygen transfer coefficient (KLa) rates. P. kudriavzevii Kp34ey (adapted and parental strain) and S. stipitis NRRLY-7124 produced the highest ethanol concentrations at a KLa value of 3.3. Overall, for all KLa values tested, the adapted strain performed better than the parental strain and S. stipitis NRRLY-7124. The adapted P. kudriavzevii Kp34ey yielded 4.03 g/L ethanol on 60 g/L xylose with 3 g/l acetic acid at 37°C at a KLa value of 3.3 and was the only yeast tested to grow under these conditions.

>Magister Scientiae - MSc / The global dependence on non-renewable fossil fuels to meet energy needs cannot be sustained for a long time and it is already evident in the escalation of fuel prices over the past decade. This research was performed towards renewable energy production from agricultural and food waste. The use of agricultural and food waste has benefits such as being grown in a land that is not in competition with food crops protein, all year round availability, and having high lipid content. The produced bio-crude oil can be upgraded to remove moisture and acidity level, and can be used as a substitute for heavy oils such as diesel to power static appliances or can be used as petrol distillate fuel alternative. Hydrothermal liquefaction (HTL) process is one of the commonly used technologies for converting agricultural and food waste into liquid biofuels.

No description available.

No / The emission of greenhouse gases on a global scale is predominantly caused by the utilization of fossil fuels. Various methods have been explored to address the recycling of CO2, which among, the CO2 conversion into high-value chemicals become so promising. The purpose of this book chapter evaluation is CO2 reduction and H2 evolution reactions for producing syngas. A comprehensive analysis shall highlight (i) the technical advantages and impediments of various reactor classifications, (ii) the effect of electrolytes on electrolyzers in the liquid phase, and (iv) the catalysts that are viable for the creation of important products such as CO.

The purpose of this study was to investigate the synthesis and properties of oxyaluminum pillared montmorillonites prepared using the controlled hydrolysis of aluminum isopropoxide as the source of pillaring species and to evaluate pillared montmorillonites as supports for hydrodesulfurization (HDS) catalysts. Several synthesis schemes were evaluated for the preparation of pillared montmorillonites. Successful pillaring was accomplished by addition of cyclohexane solutions of aluminum isopropoxide to aqueous montmorillonite suspensions. The pillared montmorillonite preparation was optimized for maximum interlayer spacing by variation of experimental parameters. Samples were characterized by x-ray diffraction and BET surface area. After dehydration a maximum interlayer spacing of approximately 6 A was obtained. As the ratio of aluminum isopropoxide to clay increased the surface area decreased. The interlayer limit was attributed to the primary pillaring species being a plate-like oxyaluminumcation having a boehmite layer structure whose thickness was about 6.1 A. Decreasing surface area for increasing aluminum to clay ratio probably resulted from exchange of larger cationic oxyaluminum plates into the interiayer volume. It was suggested that at the limit of very low surface area with a layer separation of about 6 A, the montmorillonite-oxyaluminum material consisted of alternating montmorillonite and 'boehmitem layers. / Ph. D.