Browsing by Author "Mason-Jones, Kyle"

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    Flows and fates of nickel-cadmium batteries in the City of Cape Town
    (2009) Mason-Jones, Kyle; Von Blottnitz, Harro
    Current patterns of economic activity entail high rates of material extraction from the natural environment and the generation of large amounts of waste. Alternative strategies must be found if we are to avoid the exhaustion of resources and the environment's capacity to safely absorb our wastes. Examining current resource use is an important step towards achieving a more sustainable society, and the toxic substances widely applied in our technologies form a crucial part of this examination. The heavy metal cadmium is one such substance. The use and disposal of nickel-cadmium secondary cells (the basic components of NiCd batteries) in Cape Town, South Africa, has been investigated with the objective of quantifying the associated flows of cadmium. This was achieved by applying substance flow analysis methodology to the year 2005 with a steady-state approach to quantify the disposal commitment arising from inflows in that year. Uncertainty in the calculated results was quantified by means of Monte Carlo simulation. Small sealed cells were found to make the dominant contribution to overall cadmium flows, with cordless power tools and separately imported cells accounting for most of these. Essentially all of these cells either have or will enter the municipal solid waste streams of the city. Large industrial cells made a smaller but significant contribution to overall inflows (3.4-14%), but none were known to have entered municipal waste. These went primarily to hazardous waste disposal outside the city or recycling abroad, with some going into storage. In order to assess the environmental significance of the cadmium sent to landfill, hypothetical "best worst-case" scenarios were developed which involved the worst case of total cadmium release from landfill, and best-case calculations of the potential contamination of agricultural land that could result from such release. A total release to agriculture was found to contaminate the city's croplands in under twenty years. Although these scenarios considered contamination potential but not the likelihood of contamination, and hence were not predictive, it could nevertheless be concluded that the amounts of cadmium destined for landfill disposal justified concern and caution. The disposal of environmentally significant amounts of cadmium in Cape Town and the very limited understanding of landfill behaviour necessitate the elimination ofNiCd batteries from municipal solid waste streams. Some approaches are briefly discussed by which this might be achieved, with regard to both environmental protection and resource conservation in general and the changing landscape of waste management in South Africa. Significant challenges were encountered from limited data availability during the application of substance flow analysis within a developing-world urban setting. This necessitated primary data collection and adaptation of data from other geographical and temporal scales. Adjusting national data to the city scale required the development of scaling factors which were more plausible than the use of population share or regional GDP Some similarities were noted between the cadmium metabolism of Cape Town and that of previously studied regions in the developed world. This supported the suggestion that some insights from substance flow analysis studies can be transferred to other regions when resources are not available for thorough local study. Important differences were also present, however, and further research is required to develop this possibility.