Stotko, Oliver.
Abstract:
The disposal of waste into landfill sites is currently the most commonly employed method of dealing with waste in South Africa as well as internationally. However the global trend towards operating waste management systems in a more sustainable way has lead to the need to reverse this situation towards a waste management system that predominantly makes use of waste minimization schemes to deal with waste and relies minimally on waste disposal. The focus of this research was to determine which waste minimization schemes would be most effective in the Municipal Solid Waste Management Systems (MSWMS) of Cape Town and Johannesburg with regard to achieving this reversal in an economically sustainable manner. The method used to achieve this objective was threefold, firstly requiring the development of a waste flow diagram for each respective city, followed by the development of a waste stream model based on the specific flow diagram and finally the extension of this material model into an economic model. The models were developed in Microsoft Excel and work on the premise that each particular stream (separate collected waste, transfer station waste, etc) of the MSWMS concerned has a particular associated cost (defined as cost per ton of waste processed). The model operates on the principle that under several pre-determined constraints the Excel Solver function calculates the optimal flow rates of the various waste streams which give the minimum overall MSWMS cost for future years. The developed model has shown that the recovery of waste reduces the overall MSWMS costs until a threshold value (at which point under the proposed system all economically recoverable waste has been exhausted). Different waste minimization schemes were found to be appropriate for each respective city. However, the use of Material Recovery Facilities (MRFs) to recover recyclables has been shown to be a viable waste recovery scheme for both Cape Town and Johannesburg. Cape Town is in the process of implementing the development of MRFs in conjunction with existing transfer stations, while it is envisaged that MRFs will be developed on all of Johannesburg's Municipal landfill sites in the future. Significant changes to the MSWMS of both cities are required for their respective landfilling waste streams to be substantially reduced in accordance with the Polokwane Declaration. Decreasing the landfilled waste stream is not only required by legislation, but the developed model has shown that the recovery of waste also reduces the overall MSWMS costs.
