Urban waste management poses problems in all cities of the world, but it also provides opportunities for innovative resource use. The Thesis begins by defining the waste management problem of Nairobi in context and then analytically reviews the international status of waste management, contrasting the circumstances in developed economies with those in Tropical Africa. An investigation of household refuse in Nairobi, exploring its embodied energy and its value for composting follows as the focus of the Thesis. Typical households were surveyed in relation to their waste management behaviour and agricultural activities. An attempt was made to analyse the physical and chemical composition of household refuse as well as its energy value. In addition to household surveys, a senior local government official and waste disposal crews were interviewed in order to ascertain current policies and management practices in the handling of waste. Particular attention was paid to the Eastlands area of the City. Ways in which refuse is incorporated into the food and energy cycles were identified. Among the important factors discerned are the role of family structure and the economic position of households. The validity of the research is discussed and recommendations are made for the future of waste management in relation to energy and food production in Nairobi. The findings of the research should have wide application in other African countries.

This study has investigated the use of exergy analysis when applied to the UK steel sector. The aim has been twofold: to assess whether exergy analysis provides greater insight into physical processes at this level than conventional thermodynamic analyses; and whether it can be used to identify ways that this sector has reduced its impact on the environment in the past, and how this might continue in the future. An overview of the issues surrounding resource consumption and waste generation and their relationship to the steel sector are given [Chapter 1]. The theory behind exergy analysis is then reviewed and its relevance to reducing resource use and waste minimisation examined [Chapter 2]. An exergy analysis was performed on all the processes within the steel sector [Chapters 3 & 4] and the reasons for thermodynamic inefficiencies discussed. Based on these analyses, exergy analysis was found to be superior to other methods in describing some, but not all, processes when compared with two forms of energy analysis [Chapter 5]. This is due to fact that exergy includes an account of entropy which quantifies thermodynamic quality. It was shown that reducing the exergy consumption of the steel sector leads to a reduction in resource use and to some extent will lead to a reduction in the emission of pollutants. Two different systems which could represent the UK steel sector were investigated to determine which best fitted the aims of the study [Chapter 6]. The first system was based on all processes within the UK which were linked to the use of steel; the second was based on all processes, regardless of location, which were linked to the use of steel in the UK. It was found that for the steel sector at least, there was little difference in the exergy consumption of each system, although these were structurally quite different. Finally a system was chosen to represent the UK steel sector which best suited the needs of the study. This system was used to examine the evolution of the steel sector from 1954-1994, detailing all the main steel and scrap flows, the exergy consumption in; mining, transport, steel production and scrap processing, the effects of trade and the role of manufacture and product use in generating scrap [Chapter 7]. It was found that the exergy consumption of the UK steel sector has fallen twofold in this time period, indicating a large reduction in resource consumption. Based on past evolution, scenarios for possible futures of the steel sector were constructed [Chapter 8]. These showed that from 1994 to 2019 substantial reductions in the exergy consumption of the sector are possible (between 15% and 72% of 1994 levels by 2019) through changes to: the overall demand for steel goods, the technology of steel production and the mix of steel production methods.

This thesis examines the practical engineering problems associated with high-activity radioactive waste disposal. It includes a critical review of all the available disposal options, but focuses on concepts involving deep underground burial in purpose-built repositories. The construction and waste containment properties of crystalline, argillaceous and saliferous host rocks are examined and some inherent uncertainties in predicting their performance as natural barriers to radionuclide migration are described. It is shown that repository construction can introduce anomalous migration paths via peripheral zones of disturbance, rock/backfill separation planes and structural linings unless special preventative measures are taken. For jointed rock masses, it is shown that repository excavations may short-circuit natural flow paths. Repository design proposals from the major nuclear power-producing countries are reviewed, with particular emphasis on crystalline rock repository systems. It is shown that although the international proposals demonstrate the broad feasibility of repository construction, they generally fail to achieve optimum solutions in terms of waste containment. For jointed rocks, an optimisation study is described which demonstrates how adjustment of pre-disposal strategies for conditioning high-level wastes, altering the construction sequence, and manipulating the emplacement configuration can effect reductions in repository size to mitigate against the adverse effects of discontinuities. It is shown that applying the minimum repository size philosophy to other host rocks can also produce benefits in terms of waste containment and construction costs, and some radical design alternatives are proposed incorporating relevant principles. The role of engineered barriers, in the form of high-integrity backfills and waste unit claddings, is examined. Potentially suitable backfills are identified by reference to geochemical stability and radionuclide containment properties, and cost implications are evaluated. Parametric sensitivity studies are performed to demonstrate the influence of waste unit and backfill properties on radionuclide containment, and some new practical design concepts and emplacement techniques are suggested.

Thesis is focused on the issue of waste production, collection and management in Excalibur Army, s.r.o company, at the facility in Šternberk. I have used registration and operative data acquired directly in cooperation with the service ecologist. I described the process of waste management at the facility, since its creation until its application as a secondary raw material or its transfer to the authorized personnel for its disposal either to deposition in land-fill or its combustion in the incinerator. In my conclusion, I suggest several operational, but also administrative, precautions for overall improvement of waste management in the company.

The efficient organization of waste collection systems based on bins located along the streets involves the solution of several tactical optimization problems. In particular, the bin configuration and sizing at each collection site as well as the service frequency over a given planning horizon have to be decided. In this context, a higher service frequency leads to higher routing costs, but at the same time less or smaller bins are required, which leads to lower bin allocation investment costs. The bins used have different types and different costs and there is a limit on the space at each collection site as well as a limit on the total number of bins of each type that can be used. In this paper we consider the problem of designing a collection system consisting of the combination of a vehicle routing and a bin allocation problem in which the trade-off between the associated costs has to be considered. The solution approach combines an effective variable neighborhood search metaheuristic for the routing part with a mixed integer linear programming-based exact method for the solution of the bin allocation part. We propose hierarchical solution procedures where the two decision problems are solved in sequence, as well as an integrated approach where the two problems are considered simultaneously. Extensive computational testing on synthetic and real-world instances with hundreds of collection sites shows the benefit of the integrated approaches with respect to the hierarchical ones.

The world has an energy problem and the root cause of this problem is the growing world population and the energy consumption per capita. The main source of energy, oil, is gradually running out. The use of coal, oil and fossil energy sources are polluting the planet with greenhouse gasses (GHG).Internationally waste disposal facilities are currently providing energy to industry and humans. This research determines if waste disposal facilities in South Africa can produce a viable source of energy. The exploratory research process involved structured interviews with key informants and experts in the waste disposal facility management in South Africa. A survey questionnaire was sent to waste disposal facility managers and this questionnaire was close-ended questions. The structured questionnaire consisted mainly of open-ended questions. The data collected from the questionnaires and the surveys were analysed through descriptive statistics and content analysis. The results of the research were that waste disposal facilities in South Africa, not all, could produce energy that can be integrated into the Eskom grid, and will also contribute significantly in the reduction of harmful GHG, and to the Clean Development Mechanism. / Dissertation (MBA)--University of Pretoria, 2010. / Gordon Institute of Business Science (GIBS) / unrestricted

Gypsum is produced as a waste product by various industries, e.g. the fertilizer industry, the mining industry and power stations. Gypsum waste disposal sites are responsible for the leaching of saline water into surface and underground water and create airborne dust. Gypsum waste is not only an environmental problem but has measurable economic value as well. However, all these environmental and economical concerns can be avoided should valuable/saleable by-products like sulphur and calcium carbonate be recovered from the low quality gypsum. The aim of this project was to evaluate a process for converting waste gypsum into sulphur. The process evaluated consists of the following stages: reduction of gypsum to calcium sulphide; stripping of the sulphide with CO2 gas and the production of sulphur. Thermal reduction study showed that gypsum can be reduced to CaS with activated carbon in a tube furnace operating at 1100º C. The CaS yield was 96%. The CaS formed was slurried in water. The reaction of gaseous CO2 with the CaS slurry leads to the stripping of sulphide to form H2S gas and the precipitation of CaCO3. The H2S generated was then reacted in the iron (IIII) and PIPco processes to form elemental sulphur. Sulphur with the purity between 96% and 99% was recovered from waste gypsum in this study. / Thesis (PhD)--University of Pretoria, 2009. / Chemistry / unrestricted

Please read the abstract in the front section of this document / Dissertation (MSc (Food Science))--University of Pretoria, 2005. / Food Science / unrestricted

Please read the abstract in the section front of this document. / Dissertation (MSc (Water Utilization))--University of Pretoria, 2006. / Chemical Engineering / unrestricted

No description available.