Hoque, Kazi Mohammed Rayatul (2018) Investigations into the Impacts of Prevailing Climate and Size on the Thermal Energy Efficiency of Energy from Waste Plants. Research Master thesis, Victoria University.

Abstract

Energy from Waste (EfW) is increasingly becoming an essential part of the contemporary mix of sustainable energy systems. EfW technologies consist of waste treatment processes that create energy in the form of electricity, heat or transport fuels (e.g. diesel) from a waste source. There exists a global movement towards reduction of dependence on fossil fuels and focus on exploiting renewable energy resources. Waste is available in abundance and recent studies only suggest an increasing tonnage of waste with a growing global population and diverse industries. Thermal treatment of waste has been around for over a century, with the first incinerator built in Great Britain. The social acceptance of an EfW facility has come a long way since then, with a conscious shift away from a waste landfill as a feasible solution. Generating usable EfW resources, which would otherwise go to landfill, has unquestionable environmental and economic benefits. With a large number of waste disposal operations, establishing itself amongst key solutions as part of waste management in European cities, an efficiency scaling method was developed by the European Commission to incentivize energy recovery operations. This essentially differentiates between waste disposal and energy recovery operation. The efficiency scaling method, known as R1 thermal efficiency, has been adopted by Australian Environment Protection Agencies as well. The R1 energy-efficiency formula is widely used in the assessment of the thermal energy efficiency of an EfW facility. The R1 metric amongst other efficiency indicators is a means to assess the overall useful energy extraction process from waste. This thesis addresses potential gaps that exist in the R1 formula, particularly addressing a bias in the formula towards EfW plants of larger capacity and located in cooler climate zones. An analysis on the use of the R1 formula is presented to determine the recovery status of some EfW plants. Detailed R1 computations are provided to demonstrate the application of R1 guidelines to specific EfW technologies, incineration and gasification. The study proposes the application of climate and size correction methods in consideration of the disadvantage faced by smaller-sized EfW plants or those located in warmer regions in meeting the set threshold. A key highlight is the case based application of external variants, climate and size correction factors to EfW plants in different locations in Europe, in scaling the R1 value. The proposed size and climate correction factors are compared with the Climate Correction Factor (CCF) defined in the Waste Framework Directive (WFD) of the European Union. The application of the proposed correction factors lead to conservative R1 scaling when compared with the application of the WFD CCF. The introduction of the size correction factor addresses an important gap in the current WFD. Combined heat and power (CHP) modes of EfW plants have proven to be more efficient, given there is substantial demand of thermal energy. The research analyses CHP modes and relates the outcome to the R1 criterion for the select case studies. The work is novel and the proposed analytical model makes significant contributions to knowledge by demonstrating the impacts of external variants on the outcome of R1 thermal efficiency of EfW plants. The proposed calculation tool would enable engineers, site managers, system auditors with a methodology that can be applied for the initial assessment of R1 thermal efficiency of an EfW. The comparative analysis with European WFD formula and CHP mode provides a broader spectrum to gauge the efficiency of an EfW facility. A follow-on benefit of this work is the fact that it would enable a predictive assessment on a proposed EfW facility and hence assist in addressing concerns of environmental groups.

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