Co2 Emission from Municipal Solid Waste Incinerator: Ipcc Formula Estimation and Flue Gas Measurement

Although most of the air pollutants can be removed with air pollution control facilities, the greenhouse gas (carbon dioxide) is unavoidably released into the atmosphere from the flue gas during waste incineration. The amounts of CO2 emitted from municipal solid waste incinerators are usually estimated following the guidelines set down by the Intergovernmental Panel on Climate Change (IPCC). However, there is lack of studies investigating the difference between IPCC estimation and actually measured values from the waste incinerators. In this study, the substantial CO2 emissions from Taipei City's three incinerators were compared with the estimated figures with IPCC Guidelines. In both cases, the seasonal emission data exhibit non-normal distribution. Statistical analysis depicts a significant difference of 71% in the 95% confidence interval between the emission estimated from the IPCC Guidelines and the flue gas measurements. The correlation between the waste components and the emissions was evaluated as well. The results of the correlation analysis for the components of waste material and CO2 emissions show that there is a significant correlation between plastics and the IPCC estimated emission and there is a significant correlation with garden trimmings for the measured CO2 emissions. *Corresponding author Email: [email protected] INTRODUCTION Incineration is currently the preferred treatment operation for municipal solid wastes (MSW). Theoretically and virtually, all the volatile carbon content in MSW will be converted into CO2 emissions. During incineration of MSW, most of the greenhouse gases (GHGs) in the emissions consist of CO2 and N2O, of which CO2 being higher and more important than N2O [1-3]. CO2 emissions, in particular, have played the most significant role on global warming [4]. In densely populated urban areas, the scarcity of land and a desire to promote waste disposal makes incineration, the primary alternative of waste disposal. This makes the CO2 emissions generated during the incineration process and their effect on climate change an important issue for municipal authorities to tackle with MSW management. By applying the life-cycle inventory method and incorporating a compensatory system for waste, a unit function for emissions may be set up to assess the amount of GHGs released by different types of waste disposal schemes. Studies have shown that when the different types of waste disposal methods are ranked based on their contribution to GHG, waste recycling will contribute to the smallest amount of GHG emissions, while incineration is second lowest to waste recycling [1,5-7]. The CO2 released from biomass materials (e.g. paper, food and wood waste) during incineration is excluded from the GHG assessment [1-3] and this will help to lower GHG emissions. The recovery of residual metals from incineration and the conversion of thermal energy from the burning process into electricity also offset GHG emissions. This may be due to displaced electric utility generation and decreased energy consumption for the production processes using recycled inputs [1]. The Intergovernmental Panel on Climate Change (IPCC), however, includes the fossil and biogenic CO2 emissions produced for waste incineration with energy recovery when assessing GHG emissions. Fossil CO2 emissions are included into the national emissions under the energy sector, while biogenic CO2 emissions should be included in the energy sector and report as an information item [3] for avoiding double counting 10 J. Environ. Eng. Manage., 20(1), 9-17 (2010) activity data with energy sector. While there has a separate set of guidelines for the CO2 emissions produced when waste disposal is used to generate energy, there is still some difference in emission offset between the method adopted for calculating CO2 emissions and the method used by the U.S. Environmental Protection Agency when looking at the conversion of thermal energy from waste incineration into electricity and the recovery of residual metal in the waste management sector. The default emission factors from the IPCC formula was widely used by the most communities for assessing CO2 emissions during waste incineration. Hence, it is highly possible to perceive a significant discrepancy between the assessed emissions and the actual emissions. The Kyoto Protocol requires the signatory states to commit to a reduction in GHG emissions and to set up a GHG emissions trading scheme. This makes the question of a discrepancy between the CO2 emissions released by the MSW incinerator during the burning process and the IPCC assessed value an important one. Relevant data from cities with a comprehensive waste management system are therefore needed in order to conduct an in-depth study and analysis of IPCC estimates and actual CO2 emissions. Almost every country has set environmental regulations that limit the emission of pollutants in the flue gas from incinerators when burning the waste. Environmental authorities also set methods and procedures to measure concentrations of concerned pollutants. There is, however, little regulation of CO2 emissions that could provide actual amount of CO2 generated in a MSW incinerator. The objective of this study is to investigate the difference between the IPCC default values for calculating the CO2 emissions in a MSW incinerator and the actual measured values from the flue gas during actual operations. MATERIALS AND METHODS