MSc., Faculty of Science, University of the Witwatersrand, 2011 / A survey was carried out on small and micro enterprises in the Braamfontein region of Johannesburg, to determine the aggregate compositions of solid waste materials generated and collected for recycling purposes, and to determine the attitude(s) and perception(s) of manager(s) and owner(s) of such enterprises, to the collection of solid their waste(s) for recycling purposes. A stratification method based on staff numbers was used to select 60 random samples of small and micro enterprises. Results reveal that 62% of these businesses were not collecting their solid wastes for recycling purposes, despite a high daily occurrence of recyclable (paper: 95%, plastic: 72% and organic: 68%) wastes in their daily waste streams. Low levels of collection by businesses were attributed to ‘time-factor’ issue in the collection of their recyclable wastes, while the provision of more recycling facilities in the area could improve their participation. Waste to landfill transportation trends in Johannesburg’s landfills were analyzed, as a measure of the waste problem in Johannesburg. Results suggest about 18% reductions in recycling waste materials transported to the various landfill sites in the city, from 2004 to 2008, and a 14% increase in other categories of general solid wastes for the same period. Despite the reductions in recycling waste materials recorded, the city recorded low levels of waste recovery practices for recycling purposes, particularly in small and micro scale commercial sectors. In achieving the City of Johannesburg’s wastes reduction goals, particularly the waste reduction targets set in the Polokwane Declaration, of reducing the amount of wastes disposed of by 50%, achieving a 25% reduction in disposable wastes by 2012 and to developing a zero waste plan by 2022 (City of Johannesburg, 2008), the municipality needs to play a pivotal role by providing needed recycling infrastructures, educating the society on the need for sustainable waste management and providing waste collection and management incentives.

In this paper we investigate a manufacturer's sustainable sourcing strategy that includes recycled materials. To produce a short life-cycle electronic good, strategic raw materials can be bought from virgin material suppliers in advance of the season and via emergency shipments, as well as from a recycler. Hence, we take into account virgin and recycled materials from different sources simultaneously. Recycling makes it possible to integrate raw materials out of steadily increasing waste streams back into production processes. Considering stochastic prices for recycled materials, stochastic supply quantities from the recycler and stochastic demand as well as their potential dependencies, we develop a single-period inventory model to derive the order quantities for virgin and recycled raw materials to determine the related costs and to evaluate the effectiveness of the sourcing strategy. We provide managerial insights into the benefits of such a green sourcing approach with recycling and compare this strategy to standard sourcing without recycling. We conduct a full factorial design and a detailed numerical sensitivity analysis on the key input parameters to evaluate the cost savings potential. Furthermore, we consider the effects of correlations between the stochastic parameters. Green sourcing is especially beneficial in terms of cost savings for high demand variability, high prices of virgin raw material and low expected recycling prices as well as for increasing standard deviation of the recycling price. Besides these advantages it also contributes to environmental sustainability as, compared to sourcing without recycling, it reduces the total quantity ordered and, hence, emissions are reduced.

Magister Artium - MA / The local economy of the City of Cape Town supported by formal economic activities that are carried out through modern production processes whose existence is officially recognized and benefits from the protection of the authorities, and the informal activities that exist outside official control and protection systems. There is a dynamic connection between actors in the formal sector and those in the informal sector, which is seen at the levels of production, distribution and consumption of goods and services. This research investigates the linkages between informal and formal resource recovery activities in Devon Valley Landfill Site in Stellenbosch and Bellville South Landfill Site in Bellville. The two landfill sites are at the margins on the city economy where the formal and informal sectors interact and at times collide. Notwithstanding the negative health effects associated with the informal waste collections and the fact that informal waste collectors are neglected by policy makers in many developing countries in general and in South Africa in particular, evidence from Southern Africa has shown that the informal sector fosters considerable social, environmental and economic benefits that should be preserved. Informal recyclers constitute the essential workforce of the recycling business. These recyclers have undertaken various commercial and environmental tasks as a survival strategy long before the state and private entities became interested in participating in this profitable business. Waste recycling in most developing countries is a response to the inability of the formal economy to absorb a growing urban population, and the value placed on recyclable materials in the globalized economy. The study explores the various linkages between the informal sector and formal sector in the recycling industry and it examines the activities of these people involved in informal sector activities at the bottom end of the commonly neglected waste recycling chain. It also examines how waste pickers have developed livelihoods based on resource recovery activities at Devon Valley Landfill Site and Bellville South Landfill Site. This thesis is the result of an extensive literature review and primary data collection using a mixed methods approach. Primary sources of information consulted include, waste pickers, dealers, buy-back centres and manufacturing companies. This thesis attempts to establish the respective correlation between urban poverty, informal waste collection, and the recycling industries. The findings reveal that informal recycling is intricately linked to the formal recycling sector with waste pickers selling their waste to merchants and recyclers.

Recycling has proven not only to address today’s economical, environmental and social issues, but also to be imperative for the sustainability of human technology. The current thesis has investigated the feasibility of a new philosophy for Recycling (Alloying-Recycling) using steel 1020 and aluminum 6061T6. The study was limited to the metallurgical aspects only and has highlighted the potential of recycled alloys made of recycled aluminum and steel to exhibit substantially increased wear resistance and strength-to-weight ratio as compared to initial primary materials. Three alloy-mixtures are considered: TN3 (5wt% 1020 +95wt% 6061T6); TN5 (0.7wt% 1020 + 99.3wt% 6061T6); and TN4 (10wt% 6061T6 + 90wt% 1020). A Tucker induction power supply system (3kW; 135-400 kHz) is used to melt the alloy mixtures for casting in graphite crucibles. Heat treatment of the cast samples is done using a radiation box furnace. Microscopy, Vickers hardness and pin-on-disc abrasive wear tests are performed. Casting destroyed the initial microstructures of the alloys leading to a hardness reduction in the as-cast and solution heat-treated aluminum rich samples to 60 Hv from 140 Hv. Ageing slightly increased the hardness of the cast samples and provided a wear resistance two times higher than that of the initial 6061T6 material. On the steel rich side, the hardness of the as-cast TN4 was 480 Hv, which is more than twice as high as the initial hardness of steel 1020 of 202 Hv; this hints to strong internal and residual stress, probably martensite formation during fast cooling following casting. Solution heat treatment lowered the hardness to the original value of steel 1020, but provided about ten (10) times higher wear resistance; this suggests higher ductility and toughness of normalised TN4 as compared to 1020. In addition, TN4 exhibits about 25% weight reduction as compared to 1020. The actual recycling process and the effect of non-metallic impurities shall be investigated in future works. Also, the casting and heat treatment processes need to be improved.

Recycling has proven not only to address today’s economical, environmental and social issues, but also to be imperative for the sustainability of human technology. The current thesis has investigated the feasibility of a new philosophy for Recycling (Alloying-Recycling) using steel 1020 and aluminum 6061T6. The study was limited to the metallurgical aspects only and has highlighted the potential of recycled alloys made of recycled aluminum and steel to exhibit substantially increased wear resistance and strength-to-weight ratio as compared to initial primary materials. Three alloy-mixtures are considered: TN3 (5wt% 1020 +95wt% 6061T6); TN5 (0.7wt% 1020 + 99.3wt% 6061T6); and TN4 (10wt% 6061T6 + 90wt% 1020). A Tucker induction power supply system (3kW; 135-400 kHz) is used to melt the alloy mixtures for casting in graphite crucibles. Heat treatment of the cast samples is done using a radiation box furnace. Microscopy, Vickers hardness and pin-on-disc abrasive wear tests are performed. Casting destroyed the initial microstructures of the alloys leading to a hardness reduction in the as-cast and solution heat-treated aluminum rich samples to 60 Hv from 140 Hv. Ageing slightly increased the hardness of the cast samples and provided a wear resistance two times higher than that of the initial 6061T6 material. On the steel rich side, the hardness of the as-cast TN4 was 480 Hv, which is more than twice as high as the initial hardness of steel 1020 of 202 Hv; this hints to strong internal and residual stress, probably martensite formation during fast cooling following casting. Solution heat treatment lowered the hardness to the original value of steel 1020, but provided about ten (10) times higher wear resistance; this suggests higher ductility and toughness of normalised TN4 as compared to 1020. In addition, TN4 exhibits about 25% weight reduction as compared to 1020. The actual recycling process and the effect of non-metallic impurities shall be investigated in future works. Also, the casting and heat treatment processes need to be improved.

No description available.

none

No description available.

Recycling has proven not only to address today’s economical, environmental and social issues, but also to be imperative for the sustainability of human technology. The current thesis has investigated the feasibility of a new philosophy for Recycling (Alloying-Recycling) using steel 1020 and aluminum 6061T6. The study was limited to the metallurgical aspects only and has highlighted the potential of recycled alloys made of recycled aluminum and steel to exhibit substantially increased wear resistance and strength-to-weight ratio as compared to initial primary materials. Three alloy-mixtures are considered: TN3 (5wt% 1020 +95wt% 6061T6); TN5 (0.7wt% 1020 + 99.3wt% 6061T6); and TN4 (10wt% 6061T6 + 90wt% 1020). A Tucker induction power supply system (3kW; 135-400 kHz) is used to melt the alloy mixtures for casting in graphite crucibles. Heat treatment of the cast samples is done using a radiation box furnace. Microscopy, Vickers hardness and pin-on-disc abrasive wear tests are performed. Casting destroyed the initial microstructures of the alloys leading to a hardness reduction in the as-cast and solution heat-treated aluminum rich samples to 60 Hv from 140 Hv. Ageing slightly increased the hardness of the cast samples and provided a wear resistance two times higher than that of the initial 6061T6 material. On the steel rich side, the hardness of the as-cast TN4 was 480 Hv, which is more than twice as high as the initial hardness of steel 1020 of 202 Hv; this hints to strong internal and residual stress, probably martensite formation during fast cooling following casting. Solution heat treatment lowered the hardness to the original value of steel 1020, but provided about ten (10) times higher wear resistance; this suggests higher ductility and toughness of normalised TN4 as compared to 1020. In addition, TN4 exhibits about 25% weight reduction as compared to 1020. The actual recycling process and the effect of non-metallic impurities shall be investigated in future works. Also, the casting and heat treatment processes need to be improved.

Different types of biomass samples including fungi and algae were treated for their gold and cobalt uptake capacity. The performance of activated carbon and ion-exchange resins were compared with the metal uptake capacity of the biosorbents. Sargassum natans, a brown seaweed, exhibited a high gold uptake capacity outperforming the ion-exchange resin and equalling activated carbon. Algal biomass of Ascophyllum nodosum proved to be a very potent biosorbent for cobalt. While the temperature, agitation and biomass particle size did not affect the metal uptake process, the effect of pH was significant for both gold and cobalt uptakes. The optimum pH for gold uptake was 2.5 and for cobalt, was 4-5. The kinetics of cobalt biosorption was relatively rapid (5 min) at the initial concentration of the metal in solution, 100 mg/L. The biosorptive uptake of gold required 2 h to reach equilibrium when the initial concentration of gold was 100 mg/L. None of the tested cations, such as K$ sp+$, Ca$ sp{2+}$, Fe$ sp{2+}$, Cr$ sp{3+}$, UO$ sbsp{2}{2+}$, Ni$ sp{2+}$, Zn$ sp{2+}$, Ag$ sp+$, affected the gold uptake capacity of S. natans biomass under the optimum conditions. Anions, such as NO$ sbsp{3}{-}$, SO$ sbsp{4}{2-}$, CO$ sbsp{3}{2-}$, PO$ sbsp{4}{3-}$, and Pb$ sp{2+}$ suppressed the gold uptake somewhat. Under the optimum process conditions cations, except K$ sp+$ and Fe$ sp{2+}$, and anions, NO$ sbsp{3}{-}$ in particular, exhibited a pronounced negative effect on the cobalt uptake by A. nodosum biomass. / Sequestered gold was eluted with a mixture of thiourea and ferric ammonium sulphate solution. Approximately 98% of sequestered gold was eluted with 17 h in a batch contacting system at the optimum solids (biomass)-to-liquid ratio of 5 and pH of 5. At increased temperatures, the gold elution rate increased only slightly. Efficient desorption of cobalt was achieved using CaCl$ sb2$/HCL solution at pH 3. Cobalt elution time was quite short. Temperature affected neither desorption rate nor the equilibrium. The optimum solid-to-liquid ratio was 12 for desorption of cobalt from A. nodosum biomass. / The gold taken up by the biosorbent was deposited in its elemental form. / Available mathematical models, including the REDEQL2 chemical equilibrium model, were tested for theoretical predictions of co-ion competition in attempt to better understand the biosorption mechanism. (Abstract shortened with permission of author.)