published_or_final_version / Mechanical Engineering / Master / Master of Philosophy

Hong Kong is vulnerable to energy and economic security due to the heavy dependence on imported fossil fuels. Waste has also been a major environmental management problem due to the amount of rubbish produced every year but lacking the technology and capital to manage different types properly. The objective of the dissertation is to study the feasibility of the use of biofuel in Hong Kong by recycling local waste. Current government policies in Hong Kong and overseas are being investigated on the appropriateness for domestic use. Literature reviews and stakeholders’ questionnaires are accounted to analyse the adaptability and popularity of the biodiesel application. The methodology of the dissertation is to firstly examine literature reviews regarding biodiesel’s environmental aspect, technical efficiencies, economic aspect, government incentives and tax constraints. The consensus outcome of these researches advocated high popularity of biodiesel consumption and production in Europe and U.S. due to lower environmental impact, equivalent output efficiency and strong government support. Their successful implementation is a good example to improvise biodiesel domestically in Hong Kong. Secondly, interviews were conducted with Hong Kong’s limited stakeholders. Respondents such as Hong Kong International Airport, Hong Kong Jockey Club, Fairwood Fastfood MTR Maritime Square were interviewed as these participants have been the pioneers in Hong Kong by recycling waste into biodiesel. On the production side, two out of three bio-refineries in Hong Kong provided their business sustainability and feasibility comments to pursue a long term goal. The limitation on responses might be focused solely on a few peer groups, and not the appropriate stakeholders with proper sampling size. However, the results are concurrent that biodiesel is one of the best alternative energy in Hong Kong. The dissertation draws positive results based on the following factors. Biodiesel can diminish the tremendous cost on waste management and landfill dumping. Using local food waste and industrial wastes from restaurants and food factories as feedstock to produce biodiesel is positive. This will also minimise the heavy reliance on imported fossil fuels to diversify energy sources. Refuelling of biodiesel fuel can be performed in any gas stations with the use of the existing infrastructure without any further requirement of new investment. Nonetheless, in order to facilitate the use of biodiesel, incentives programmes initiated by Hong Kong Government and the biofuel producers have to coherently promote this alternative fuel. The conclusion states that Hong Kong is completely feasible to adopt the use of biodiesel in medium to heavy sized vehicles and vessels in the commercial sector. The environmental benefit of Hong Kong using biodiesel stood out compared to other form of renewable energy. / published_or_final_version / Environmental Management / Master / Master of Science in Environmental Management

Typescript (photocopy). / Digitized by Kansas Correctional Industries

A Thesis submitted to the Faculty of Science, School of Chemistry at University of the Witwatersrand, in fulfilment of the requirements for the degree of Doctor of Philosophy. Johannesburg, 2015. / Photovoltaic cells offer a good alternative to the fossil fuels. Several approaches are being analysed in order to have solar cells that are capable to conquer the energy market all around the world. Quantum dots (QDs) have already proven features that can be taken into account to improve the properties of solar cells. Metal selenide nanoparticles (NPs) possess semiconducting behaviours that can vary with their structural and optical properties evolving from their synthesis. The reaction parameters such as the method, time, solvent and precursors can affect the growth and nucleation of particles and thus impose on the properties of the synthesized materials. The performance of solar cells made of the synthesized metal selenides will then be dependent upon the properties of the NPs used as active layer. Furthermore, the electrical current generation also depends on the structure of the deposited active layer and its interface with other films to be assembled for the device. The binary copper selenide, ternary copper indium selenide (CISe), quaternary copper indium gallium selenide (CIGSe) and quinary copper zinc tin sulphur selenide (CZTSSe) NPs were synthesized via conventional colloidal method (CCM) and microwave assisted method (MAM). The MAM has a particular interest as it is less time consuming and can easily be a large scale synthesis. Photovoltaic devices were fabricated from the synthesized materials as proof of concept for photovoltaic activities. The CCM was used to optimize various parameters for the synthesis of each type of the chalcogenide materials as this is easily controllable than the ones from the sealed vessel from MAM. The dependency of properties of all copper chalcogenide NPs on the time, precursor concentration, temperature and solvent of synthesis have been demonstrated via various characterization techniques including ultraviolet-visible-near infrared spectroscopy, photoluminescence spectroscopy, X-ray diffractometry and transmission electron microscopy. The binary copper selenide was first synthesized and considered as a template for evaluation of the use of copper chalcogenide materials in solar cells. Relatively smaller copper selenide NPs with average sizes of 4.5 and 6.0 nm were obtained from conventional colloidal and microwave assisted methods respectively. The sample yielded from the microwave assisted method possessed less polydispersed NPs. The later had better crystallinity in which prevailed a single cubic Cu2Se phase. To the best of our knowledge this is the first evidence of defined shapes and nearly single phase of small sized copper selenide NPs synthesized by mean of the MAM. The copper selenide particles synthesized via this method were used to fabricate a Schottky device. The conditions of copper selenide synthesis were optimized to 250 oC, 30 min of CCM synthesis using oleylamine (OLA) and a Cu/Se ratio of 1:1. Nearly hexagonal facets with blue-shifted absorption band edge of monodispersed NPs sizing 4-8 nm in diameter were obtained. The synthesized copper selenide showed better crystallinity with a single cubic Cu2Se phase. A Schottky device using MAM synthesized copper selenide NPs as the semiconducting layer was fabricated at room temperature. The diode effect was demonstrated with the electrical parameters such as the ideality factor, barrier height and the series resistances extracted from the experimental current-voltage data using the thermionic theory and Cheung’s modification. The thermionic theory resulted in the ideality factor of 4.35 and the barrier height of 0.895 eV whilst the Cheung’s method resulted in the ideality factor, barrier height and series resistance of 1.04, 2.59 10-3 eV and 0.870 Ω respectively. The ternary copper indium selenide NPs showed that the MAM allowed the formation of copper rich NPs alongside secondary products. The synthesis of the ternary sample via CCM was optimized using uncapped precursors (no TOP was added) in OLA at 220 oC for 30 min. The synthesized CuInSe2 NPs possessed a large blue-shift in their absorption band edges and emission peaks. The nearly stoichiometric CuInSe2 particles with diameter sizes of 5-9 nm were found in tetragonal crystalline orientation. The cyclic voltametry (CV) and the absorption spectra showed a large blue-shifted energy gap, about 0.95 eV, an increase from the bulk, proving the quantum confinement effects of synthesized copper indium selenide quantum dots. The CuInSe2 NPs were thus used as absorbing materials in the quantum dot sensitized solar cell devices (QDSSCs). The QDSSC devices were assembled via treatment of the titanium oxide, quantum dot layers and their interface. This was done by the treatment of copper indium selenide surface with mercapto-propionic acid (MPA) and ethanedithiol (EDT) during the deposition of the quantum dots onto TiO2 films. The MPA treatment did not reveal positive effects on copper indium selenide thin film and the assembled device under our optimized working conditions. However the use of EDT allowed the improvement of electron transport. The short circuit current (Jsc), open circuit voltage (Voc) and fill factor (FF) obtained from the current-voltage (J-V) curves reached the values of 324 μA cm-2, 487 mV and 43% respectively, indicating that the investigated quantum dots possess electrical properties. For the quaternary copper indium gallium selenide, relatively small sized NPs were synthesized via CCM and MAM. The CCM synthesized CIGSe NPs were less agglomerated with a shorter tailing in absorption than those from MAM. The stoichiometric CuIn0.75Ga0.25Se2 showed less agglomerated and highly crystalline particles with a large blueshifted absorption band edge and a smaller full width at halth maximum (FWHM) of the emission peak compared to CuIn0.5Ga0.5Se2 and CuIn0.25Ga0.75Se2. The use of OLA as solvent of synthesis improved the growth and dispersivity of copper indium gallium selenide NPs. The particles with a large blue-shifted absorption band edge, a lattice of tetragonal phase, more monodispersed CIGSe and possessing an average size of 6.5 nm were obtained from CCM synthesis using OLA. The OLA as-synthesized CIGSe NPs were used in thin film for the assembly of QDSSC. The device exhibited electrical properties with the Jsc, Voc and FF of 168 μA cm-2, 162 mV and 33% respectively. The overall device performance was poor but may further be improved for further photovoltaic application. The quinary CZTSSe NPs possessed large blue-shifted absorption band edges of 450-460 nm than the bulk material (827 nm). The emission peak at 532 nm and similar FWHM of less than 50 nm were observed in samples from both CCM and MAM. More monodispersed crystals were obtained with both methods whilst the average particle sizes of 10 and 9 nm were yielded from MAM and CCM respectively. The nanoparticles crystallized in tetragonal lattices between copper zinc tin sulphide and copper zinc tin selenide crystals. However, the MAM gave more crystalline phases. The CV and the absorption spectra showed a blue shifted energy gap, about 0.21 eV increase from the buk which is located at 1.51 eV. This is indicative of the quantum confinement effects of synthesized NPs. The evidence of electrical properties was also shown in the QDSSCs fabricated using the MAM synthesized quinary QDs. This was done following the same treatments as for copper indium selenide devices. The Jsc, Voc and FF were found at the maxima of 258 μA cm-2, 395 mV and 38% respectively. The MPA and EDT treatments did not improve the device performance under our working conditions. Nevertheless, the electrical properties observed in the assembled device were indicative of promising efficient solar cells from synthesized CZTSSe NPs.

The scarcity of fossil fuel and its environmental impact have shifted the world focus on green innovations At a time when the use of fossil fuel means increasing energy scarcity and an environmental crisis in the world in which we live, we need green innovations now more than ever. Growing attention has been drawn to the use of biofuels, such as bioethanol and biodiesel, which have gradually come to make up part of the total energy supply. Uncertainties about the environmental and ecological aspects of the production and consumption of biofuel still exist despite its rapid development. A life cycle analysis (LCA) evaluates the two principal functional parameters 1) energy efficiency and 2) Greenhouse Gas (GHG) balance of different feedstocks for biodiesel production from the cradle to the grave. By accounting a life cycle analysis stage by stage, we can ascertain the change in GHG emissions and energy demand that result from the various uses of feedstocks for the production of biodiesel. In this thesis, various life cycle analysis models are reviewed and evaluated with emphasis on specific biofuels. Different LCA models depend on different LCA calculation under different situations, including GREET, LEM, SimaPro, etc. The software SimaPro was used to compare the life cycle GHG emissions and energy demand from conventional petroleum fuels and several hydro-processed renewable green diesels. A consistent methodology was used for selected fuel pathways to facilitate relatively equitable comparisons. The building of life cycle flow tree in SimaPro combined the input and output with an emphasis on the following stages 1) raw material farming and acquisition, 2)liquid fuel production, 3)transport, 4)refueling, 5)liquid fuel conversion to biodiesel and 6) end uses. Consistent impact assessment methods were chosen for simulation, equitable comparisons and comprehensive analysis of selected fuel pathways for the calculation of Global Warming Potential (GWP) and Cumulative Energy Demand (CED). However, the results of the entire lifetime estimates vary dramatically in production chains, which make it difficult to take a holistic view about energy intake and yields, economic costs and values, environmental impacts and their benefits. Apart from the diversity in system boundaries and life cycle inventories, a variance in terminologies and the limitations of interdisciplinary communication are the main factors that affect the quality of the results. / published_or_final_version / Mechanical Engineering / Master / Master of Philosophy

Respirometric experiments were performed to evaluate the role of nitrogen in aerobic diesel biodegradation. Specific objectives included 1) evaluating the effects of water potential induced by various nitrogen amendments on diesel biodegradation rates in arid region soils, 2) comparing concurrent effects of C:N ratios and soil water potential on diesel degradation rates, and 3), measuring gross rates of nitrogen cycling processes in diesel-contaminated soil to determine duration of fertilizer bioavailability. In all studies, increasing nitrogen fertilization resulted in a decrease in total water potential and correlated with an increase in lag phase and overall reduction in microbial respiration. Highest respiration and estimated diesel degradation was observed in the 250 mg N/kg soil treatments regardless of diesel concentration, nitrogen source, or soil used, suggesting an inhibitory osmotic effect from higher rates of nitrogen application. The depression of water potential resulting in a 50% reduction in respiration was much greater than that observed in humid region soil, suggesting higher salt tolerance by microbial populations of arid region soils. Due to the dependence on contaminant concentrations, use of C:N ratios was problematic in optimizing nitrogen augmentation, leading to over-fertilization in highly contaminated soils. Optimal C:N levels among those tested were 17:1, 34:1, and 68:1 for 5,000, 10,000 and 20,000 mg/kg diesel treatments respectively. Determining nitrogen augmentation on the basis of soil pore water nitrogen (mg N/kg soil H₂0) is independent of hydrocarbon concentration but takes into account soil moisture content. In the soil studied, optimal nitrogen fertilization was observed at an average soil pore water nitrogen level of 1950 mg N/kg H₂0 at all levels of diesel contamination. Based on the nitrogen transformation rates estimated, the duration of fertilizer contribution to the inorganic nitrogen pool at 5,000 mg/kg diesel was estimated at 0.9, 1.9, and 3.2 years in the 250, 500, and 1000 mg/kg nitrogen treatments respectively. The estimation was conservative as ammonium fixation, gross nitrogen immobilization, and nitrification were assumed as losses of fertilizer with only gross mineralization of native organic nitrogen contributing to the most active portion of the nitrogen pool.

published_or_final_version / abstract / toc / Mechanical Engineering / Master / Master of Philosophy

This study presents an experimental investigation into the effects of running biodiesel fuel blends on conventional diesel engines. Bio fuels provide a way to produce fuels without redesigning any of the engine technology present today, yet allowing for green house emissions to decrease. Bio-diesel is one of these types of emerging bio-fuels, which has an immediate alternative fuel aspect to it, while providing a decrease in green house emissions, as well as a solution to recycling used Waste Vegetable Oils which are other wise disposed. This study shows how by blending bio-diesel with petroleum diesel at intervals of B5, B10, B15, and B20 decrease green house emissions can significantly while maintaining similar performance output and efficiency with respect to 100% petroleum diesel. / by Sergio Bastiani. / Thesis (M.S.C.S.)--Florida Atlantic University, 2008. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2008. Mode of access: World Wide Web.

Abstract not available

Thesis (Master of Engineering in Chemical Engineering)--Cape Peninsula University of Technology, 2018. / The production of biodiesel is an energy and water intensive process. The wastewater that is produced during this process is high in concentrations of COD, BOD, FOG and various other contaminants. Since it contains low levels of nutrients, it is difficult to degrade using natural processes such as conventional activated sludge wastewater treatment. The discharge of untreated biodiesel wastewater also raises serious environmental concern. It interferes when remediated with biological processes and results in additional costs during the production of biodiesel when penalties and fines are applied. Conventional treatment processes are not capable of treating contaminants and pollutants in biodiesel to satisfactory concentrations and hence advanced treatment processes are necessary. In this research, a lab scale integrated treatment process was used to investigate the successful reduction of contaminants, in particular COD, BOD and FOG. The integrated treatment process used in this study consisted of three consecutive steps; acidification, electrochemical oxidation and adsorption using chitosan as an adsorbent. The electrochemical oxidation process with IrO2-Ta2O5/Ti anodes was applied to treat biodiesel wastewater. Different operating conditions were tested to establish favourable conditions. The current density applied as well as the concentration of NaCl as the supporting electrolyte greatly affected the process. A NaCl concentration of 0.08M was deemed sufficient, whereas a current density of 1 mA/cm² showed superior performance compared to lower or higher current densities. Adsorption of pollutants in biodiesel wastewater was investigated using Chitosan as the adsorbent. Various chitosan concentrations, initial pH of the wastewater and repetitive adsorption stages were investigated. It was discovered that all three operating conditions greatly affect the performance of the process. The three consecutive adsorption stages using a chitosan concentration of 4.5 g/L at a pH of 2 resulted in the highest pollutant removal. It was observed that the integrated treatment process could reduce COD, BOD and FOG levels by 94%, 86% and 95% respectively. This concludes that the treated effluent complies with local industrial effluent discharge standards, which could be disposed safely without further treatment.