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 in terms of achieving this turnaround in an economically sustainable manner. The model works on the principle that the Excel Solver function calculates, under various predefined constraints, the optimal flow rates of the various waste streams that give the minimum overall MSWMS cost for future years.
CONTEXT
OVERVIEW OF RELEVANT LEGISLATION
NATIONAL AND PROVINCIAL LEGISLATION
The purpose of this statement was to confirm the need to implement the waste hierarchy concept in the South African waste management industry. Industries were encouraged to make use of the waste hierarchy concept to minimize their waste.
LOCAL AND MUNICIPAL LEGISLATION
LITERATURE REVIEW
OVERVIEW OF WASTE MANAGEMENT MODELLING
- MODEL TYPE 1: COST BENEFIT ANALYSIS
- MODEL TYPE 2: LIFE CYCLE ASSESSMENT
- MODEL TYPE 3: MULTI-CRITERIA DECISION ANALYSIS
It generally involves optimizing a given waste management system by determining the combination of waste management schemes that result in the lowest operating costs. This type of model evaluates the performance of different waste management schemes in a multidimensional way that allows for the inclusion of multiple variable criteria in the model.
WASTE MANAGEMENT SCHEME BACKGROUND
- LANDFILLS AND LANDFILL CHARACTERISATION IN SOUTH AFRICA
- TRANSFER STATIONS
- COMPOSTING
- DROP-OFFS
- MATERIAL RECOVERY FACILITIES
Xecutech SP 4, and its function is to turn the shredded garden waste to allow re-aeration of the shards. The decomposition factor represents the fraction of the original organic mass that remains after decomposition.
METHODOLOGICAL APPROACH
MODELLING METHODOLOGY
As already mentioned in Chapter 2, an IWMP inevitably creates an interrelated relationship between the various waste management schemes used in that particular plan, so the development of an effective IWMP can only be done using the type of model that can take into account the impact of one scheme on another . Developing a model from the initial stage rather than building a model based on a pre-existing modeling software package results in a greater inclusion of local conditions and requirements of the waste management system, so CBA-type models have been found to be preferred over LCA-type models.
COMPUTATIONAL METHODOLOGY
- DEVELOPMENT OF THE FLOW DIAGRAM
- DEVELOPMENT OF THE WASTE STREAM MASS BALANCE
To develop the waste stream mass balance (WSMB) in Excel, a workbook was divided into two sheets, the first (called the Data Sheet) containing all the data required for the waste stream analysis and the second (called Flowsheet). consisting of a series of columns representing the different flows present in the particular waste management system in question. The data sheet is shown in the figure below, and contains fixed and input data.
1.00 Table A4: Analysis of Overall Waste Generated {Mega-Tech, May 2004)
DEVELOPMENT OF THE COST MINIMIZATION MODEL
The stream example illustrated in Figure 3.3 is organic recovery stream, which includes all the council-based organic recovery schemes that produce compost product. The first value shown in this section is the variable operating cost, which is multiplied by the total flow rate of the stream to give the operating cost shown in the subsequent row.
CASE STUDY OF CAPE TOWN'S WASTE STREAM
INTRODUCTION
- BACKGROUND
- OBJECTIVES OF STUDY
- CONTEXT
Cape Town currently uses six different landfills to dispose of waste generated in the city. Therefore, due to the urban expansion of Cape Town, the only area containing sufficient land space (that is suitably separated from residential areas) for the development of the proposed regional landfill site lies in the northwestern section of the city.
REQUIRED METHODOLOGICAL DATA
- FLOW DIAGRAM DATA
- WASTE STREAM MASS BALANCE DATA
- COST MINIMIZATION MODEL DATA
In terms of the combined flow of collected waste, the collection cost was determined by dividing the operational cost for collection services by the total amount of waste collected by the City Council (which includes discarded waste and all household waste of generated unreturned). As seen in Table 3.3, the first term of the capital cost reported for composting facilities (representing the composting of general household waste) is reported as an annual service charge (annual payback value), and therefore this term does not divided by the number of years of capital payment. The garbage truck is multiplied by the coefficient of the total flow rate of the collection of separate bodies and the value 2772.
RESULTS AND DISCUSSION
- MATERIAL FLOW RATE RESULTS
- ECONOMIC RESULTS
The Recycling Stream (Centres) was given the constraint that the bulk of this stream cannot go below the initial value reported for 2005/2006 as a result of the fact that this sector represents private recycling operations that are unlikely to decline. As shown in Figure 4.5, the increases in waste recovery rates generated for both the model and target values are quite parallel from 2005-2020. Due to the fact that the operating costs of the composting plants are higher than the income generated by them, the model only favors these recovery schemes because they allow greater inputs of material to the income-generating MRFs.
SENSITIVITY ANALYSIS
CASE STUDY OF JOHANNESBURG'S WASTE STREAM
INTRODUCTION
- BACKGROUND
- OBJECTIVES OF STUDY
- CONTEXT
The Chloorkop Landfill is located in the Kempton Park area, which lies outside the northeastern boundary of the Johannesburg Municipality. The Linbro Park landfill is expected to close by the end of 2006, which will result in greater amounts of waste from the northern areas of the Johannesburg Municipality being sent to the Chloorkop landfill. Waste generated in the immediate vicinity of the Linbro Park landfill will be sent to the Marie Louise landfill once the former landfill is closed.
REQUIRED METHODOLOGICAL DATA
- FLOW DIAGRAM DATA
- WASTE STREAM MASS BALANCE DATA
- COST MINIMIZATION MODEL DATA
Values for the total amount of waste generated for future years were extracted from Appendix 18 of the City of Johannesburg's Solid Waste Management Status Quo report. The operating costs for the Unloading Garden Waste Composting Plants reported in Table 5.2 were determined using the following website, available at the. The garbage truck is multiplied by the quotient of the total commercial organic collection flow rate and the value 4015.
RESULTS AND DISCUSSION
- MATERIAL FLOW RATE RESULTS
- ECONOMIC RESULTS
As shown in Figure 5.5, the recovery rates determined by the model increase until 2020, at which point the recovery rate reaches a maximum threshold value and remains constant at this value of 31.3% for the following years. To inform decisions on how to appropriately increase recovery rates of waste generated in line with target values, it is imperative to analyze the composition of waste designed to be sent to landfill. Organic waste recovery is necessary if a significant amount of the generated waste stream is to be diverted from landfill.
SENSITIVITY ANALYSIS
CASE STUDY COMPARISONS
ECONOMIC DATA COMPARISON
As shown in Table 6.2, the landfill waste disposal fee reported for Cape Town is significantly lower than the disposal fee charged by Pikitup in Johannesburg. Most of the capital cost equations reported in Table 5.3 above are equivalent for both Cape Town and Johannesburg. In comparing the capital costs of Organics Collection for the two cities, the annual waste truck collection capacity for Cape Town and Johannesburg should be compared.
MATERIAL FLOW RATE COMPARISONS
- COMPARISON OF RESULTANT MODEL STREAM FRACTIONS
- COMPARISON OF QUANTITY AND TYPE OF RECOVERED MATERIAL
- COMPARISON OF LANDFILL WASTE COMPOSITION
Due to this limitation, the model favors separate collection of organic waste in Cape Town because this scheme helps to regulate the quality of waste sent to mixed MRFs. The reason for the higher recycling of recycled materials in Cape Town is again due to the fact that the marginal recycling rate in Cape Town is higher than in Johannesburg and thus the recycling of recyclable materials is higher in Cape Town. The following figure shows the composition of waste sent to landfill for the model year 2030/2031 for Cape Town and Johannesburg.
OVERALL MSWMS ECONOMIC COMPARISON
All of these reasons help to explain why it makes particular economic sense to minimize waste to be collected and disposed of in the Cape Town region. Only the Cape Town model incurs capital costs large enough to result in a total MSWMS cost that exhibits a specific payback period. The payback period for the necessary changes to the Cape Town MSWMS was determined to be approximately 18 years.
CONCLUSIONS AND RECOMMENDATIONS
CAPE TOWN CASE STUDY
- CONCLUSIONS
- RECOMMENDATIONS
In order for the City Council to meet its targets to reduce the amount of waste sent to landfill, it must adopt a waste recycling scheme that works best with the future MSWMS described above. In light of this, the model has shown that it is in the interest of the City Council to provide airspace credit subsidies to the private organizations currently carrying out recycling operations in the city until the MRF/Compost Facility recycling scheme is in place. The replacement of landfill closures with transfer stations should be implemented to ensure a sustainable waste management system in the city.
JOHANNESBURG CASE STUDY
- CONCLUSIONS
- RECOMMENDATIONS
CASE STUDY COMPARISON
- CONCLUSIONS
- RECOMMENDATIONS
Coetzee, J., Botes, F. Economic Feasibility Study: Helderberg, Oostenberg and Tygerberg Transfer Stations"; Presentation given to City of Cape Town Solid Waste Management August 2005. Presented to Cape Town Solid Waste Management as part of the City's Integrated Waste Management Plan; Contract No. City of Cape Town Draft Assessment Report";. Presented to the Cape Town Solid Waste Management Department as part of the City's Integrated Waste Management Plan; contract no.
APPENDIX A
APPENDIX A 1: City of Cape Town data sheet (continued) Table A1.4: Analysis of total waste generated (Mega-Tech, May 2004). APPENDIX A2: Data sheet for Johannesburg City Table A2.1: Characterization of waste from Cape Town (Mega-Tech, May 2004). APPENDIX A2: City of Johannesburg data sheet (continued) Table A2.4: Analysis of total waste generated (Mega-Tech, May 2004).
APPENDIX B
Recycled waste (2 bags) Separate organic waste collected Recycled waste (Centres) Council composted waste.
Waste Recycle (2 bags) Separate Organic Collection Waste Recycle (Sentra) Dump Waste Recycle Dump Waste disposed of.
APPENDIX C
Combined Collected Waste Total Flow Rate: Sum of component flows
Waste source mass fractions (Black): These values for the Johannesburg model are reported in Table A2.4 of Appendix A2, where: I = Hshd (Domestic waste); C&I (Commercial/Industrial Waste);. Mass fractions of different green waste sources (Ui): Values reported in Table A2.2 of Appendix A2, where: I = DO (Drop-off); SB (service bin filling); SC (Street cleaning). Mass fractions of discarded green waste that are recovered/not recovered (Vi): Values reported in Table A2.3 of Appendix A2, where: I = R (GW recovered); NR (GW not recovered).
APPENDIX D
In the report on the status of solid waste management of the City of Johannesburg (Jarrod Ball & Associates, 2003), only three service operating costs were directly identified, namely RCW (circular collected waste), bulk services and depot management. These and other inclusive operating costs were apportioned to these two segments using the established overhead proportion for landfill operations of 0.2472. The operating costs of the daily newspaper, garden waste and informal settlement services were determined using the service cost share estimates provided in Jarrod Ball & Associates (2003).
