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A techno-economic evaluation of a waste-to-energy grate incineration power plant for a small South African city
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South Africa is currently facing power shortages due to an increased demand, a failure to invest in additional capacity and insufficient maintenance. Likewise, over the years, municipal solid waste (MSW) generation and management problems have exhibited an upward trend. Furthermore, a significant amount of energy is wasted in the country’s landfill and illegal dumping is rampant. Global trends show that there is a shift towards MSW management strategies that support the goal of sustainable development. Concurrently waste-to-energy (WtE) thermal technologies have the potential to achieve sustainable waste management goals. South African cities are no exception to power shortages, high unemployment rates and MSW generation and management problems, with landfill and illegal dumping dominating waste management strategies. WtE thermal technologies can be used to harness energy wasted in South African cities’ landfill, simultaneously creating employment. The purpose of this study is to perform a techno-economic evaluation of a WtE grate incineration power plant for a small South African city in the North-West Province, Potchefstroom. Literature on WtE thermal technologies were surveyed and a technological and performance qualitative assessment was performed. This was followed by quantitative evaluation using an analytical hierarchy process (AHP). The results obtained proved that grate incineration is more economically viable than many other WtE thermal technologies. Factors that affect WtE grate incineration power plants in South Africa are examined using strengths, weaknesses, opportunities and threats (SWOT) analysis. Tlokwe municipality (Potchefstroom) was used as a case study; its MSW generation and management data were gathered and analyzed. The drivers of WtE grate incineration in South Africa include an average of 90% dominance of landfill over other MSW management strategies, average MSW generation growth rate of 3% per annum, national power shortages, the intermittent nature of solar and wind energy and non-energy recovery methods used in treating health care risk waste (HCRW). However, lack of landfill diversion measures, high capital investment and the local culture of non-payment for services are obstacles in implementing WtE grate incineration technology. A financial analysis model with four different scenarios was formulated with the objective of determining the financial feasibility of a WtE grate incineration power plant for a small South African city. Net present value and internal rate of return were used as financial indicators. Sensitivity analysis was performed on four parameters, namely electricity price, power generation efficiency, MSW and medical waste gate fees. Financial and sensitivity analyses show that a scenario characterized by MSW and medical waste as feedstock, owned by an independent power producer yielded the best financial performance results. This scenario show feasible and most attractive investment option with capital cost of R734.40 million and simple payback period (SPB), return on investment (ROI), net present value (NPV) and internal rate of return (IRR) of 10 years, 10%, R681.77 million and 21.21% respectively. The scenario in which MSW is feedstock and owned by an investment company yield the least favorable financial performance results. The conclusion reached is that the price of electricity and medical waste gate fees are the major factors affecting WtE grate incineration power plant financial viability. Investment in a WtE grate incineration power plant is financially feasible on condition that medical waste is diverted to the plant and a waste processing annual throughput of more than 200 000 tonnes of MSW per annum is achieved. The investment became more attractive through accessibility of capital investment subsidy. A results verification process was performed by means of sensitivity analysis, surveys and consultation with experts in the WtE grate incineration technology industry, as well as publication of the results in the peer-reviewed conference proceedings of the Southern African Universities Power Engineering Conference (SAUPEC) 2015 and the Industrial and Commercial Use of Energy (ICUE) 2015
- Engineering