Technical Development of Waste Sector in Sweden: Survey

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MASTER’S THESIS IN ENVIRONMENTAL STRATEGIES RESEARCH Figure 13: Case 1- System boundary for Pyrolysis-Gasification of MSW Case 2: A comparative study of Pyrolysis-Gasification and Incineration process of LCA model is done in case 2 where both the processes handle 1 ton of MSW for the model. Transportation of waste is not considered and all emissions from the process are considered as the outflow from the system. Energy and final residue from the system are also accounted for the model. A simplified comparative LCA model is shown in the Figure 14. Figure 14: Case 2- System boundary for three different MSW treatment processes KUNGLIGA TEKNISKA HÖGSKOLAN 42 | Page
MASTER’S THESIS IN ENVIRONMENTAL STRATEGIES RESEARCH 5.3.4 Assumptions and Limitations The following assumptions have been made during the LCA model development: • For both scenarios, transportation of waste has been ignored by assuming that transportation distance for waste is same for both treatment plants. • Average energy data is considered for the model assuming the similar impact on the model for the two processes. Average data are taken for Sweden context. • Data is based on UK’s waste treatment facilities. However, we assume that electricity that is consumed by the systems will be quite similar with the Swedish perspective, so electricity consumed by system is assumed to come from the Swedish national grid (medium voltage). • CO 2 data for P-G is assumed to be same as incineration of MSW because same waste type with same carbon content would be combusted in the two different processes. This assumption is made due to the lack of carbon data for P-G process. 5.3.5 Life Cycle Inventory Analysis Life cycle inventory of the LCA model is made based primarily on the literature, report and publications and some of the important papers are DEFRA (2004), Feo et al., (2003), Bridgwater (1994), NSCA (2002), Halton EFW Business Case (2007), Cherubini et al., (2008), Finnveden et al., (2000), Circeo (2009), Khoo (2009). LCA Model has been developed based on the inflowoutflow material data that are available from the reference sources. It is important to understand and decipher the data quality and reliability of the data while developing a comparative model. It should be asserted that, the mountable data for P-G process is not available in Sweden since, there are no P-G plants in large projects in Sweden. However, the data gathered for the LCA model is quite effective for developing LCA model since data for LCA is not adversely available for emerging technologies. Data Analysis In the LCA model of Pyrolysis-Gasification, the input data is takenas waste resource (1 ton MSW), energy (electricity kWh/ton of MSW), emission (gm/T) in air, soil or waster, Energy generation (kWh/ton of MSW) and residue (kg/ton) produced by the facilities. Most of the data that is used for the LCA model is based on the waste composition in UK. Typical waste composition is shown in the appendix Table A1. Both technologies require startup energy and both generates energy from the waste treatment facilities and final residues are generated from the processes. Table 8 shows the Inflow-outflow energy and solid waste from the processes. Table 8: Input-output (energy and residue) in different MSW treatment processes Input/output Pyrolysis-Gasification Incineration Start-up energy (kWh/T) 339.3 (3) 77.8 (1) Energy generated(kWh/T) 685 (4) 544 (4) Solid residue (kg/T) 19.6 (3) 180 (2) (1) Finnveden et al., (2000), (2) DEFRA (2004) , (3) Khoo(2009), (4) Circeo (2009) KUNGLIGA TEKNISKA HÖGSKOLAN 43 | Page
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