Choosing the Municipal Waste Management Scenario with the Life Cycle Assessment (LCA) Methodology

Transcription

1 Katarzyna Grzesik 1, Mateusz Jakubiak AGH University of Science and Technology Logistyka - nauka 2 Choosing the Municipal Waste Management Scenario with the Life Cycle Assessment (LCA) Methodology Introduction Planning the integrated municipal waste management systems is extremely challenging. Such systems should meet various criteria: technological, economic, social and environmental, put differently, waste management systems should be technologically correct, economically effective, socially accepted and environmentally friendly. Effectiveness and viability of the planned municipal waste management system depends strongly on the organisation of the logistic processes within such a system. An important role play properly designed basic logistic processes: storage, collection and transportation of waste. The logistic issues of municipal waste collection and transport have been discussed in many publications, for example: [5, 6, 7]. However the superior objective of any waste management system should be to minimize the negative effects of waste on human health and the environment. Such a record is found in the Waste Framework Directive [2]: The first objective of any waste policy should be to minimise the negative effects of the generation and management of waste on human health and the environment. Waste policy should also aim at reducing the use of resources, and favour the practical application of the waste hierarchy. The Directive 2008/98/EC [2] defines waste hierarchy as 1) prevention; 2) preparing for re-use; 3) recycling; 4) other recovery, e.g. energy recovery; and 5) disposal. However, it is possible to depart from the hierarchy where this is justified by life-cycle thinking on the overall impacts of the waste management system. Although the priority is given to re-use and recycling, what requires selective collection of recyclables, such as: paper, glass, metal and plastics, the vast majority of municipal waste in Poland is collected as residual (non-selectively collected) waste. According to Polish law [11] residual municipal waste should be treated only at a regional installation. The status of regional installation could obtain: an incineration plant or a mechanical biological plant. Landfilling of residual waste should be minimized, aiming to zero landfill. The preference of waste treatment technology for residual waste should be based on a scientific method e.g. life-cycle thinking tool such as Life Cycle Assessment (LCA) methodology. The aim of this study is comparing three scenarios for residual municipal waste treatment in Krakow, with application of the Life Cycle Assessment methodology and indicating the scenario with the lowest negative impact on the environment. 1 PhD K. Grzesik, assistant professor, AGH University of Science and Technology, Faculty of Mining Surveying and Environmental Engineering, Department of Environmental Management and Protection, 2 PhD M. Jakubiak, assistant professor, AGH University of Science and Technology, Faculty of Mining Surveying and Environmental Engineering, Department of Environmental Management and Protection 4303

2 Materials and methods The Life Cycle Assessment method for evaluating waste management systems The Life Cycle Assessment (LCA) is a tool for evaluating environmental burdens associated with a product, process, or service resulting from all stages in the product or service life cycle, it is a cradle-to-grave approach. LCA enables the estimation of the environmental impacts by identifying energy and materials used and emissions released to the environment [9, 10]. Life Cycle Assessment initially developed for evaluation of a product s life cycle, could be employed for evaluating environmental performance of the waste management systems. The assessment time frame stretches from the moment, when waste is generated until its final disposal take place. The main advantage of using LCA on solid waste management systems is that the approach in a systematic way covers all impacts associated with the waste management, including all processes in the solid waste system as well as upstream and downstream [1, 4]. This study is carried out by using the EASETECH model, a new model based on the concept of EA- SEWASTE, developed by Technical University of Denmark [4]. The model has a database including recovery, treatment and disposal options, as well as external processes. The model calculates emissions to air, water and soil and any consumption of resources. Valuable products such as recycled materials or energy arising from the waste recovery are considered as substitutes for virgin materials or energy, and they are subtracted from the other emissions and resource consumptions from the waste system. For translation of the emission and resource consumption into environmental impacts, the model applies the life cycle impact assessment (LCIA) methods [4]. One of these method is EDIP 2003, which calculates environmental impacts as normalized potential impacts. Normalization presents a relative expression of the environmental impact or resource consumption compared with that of one average person (i.e. normalization reference), providing a normalized impact potential in the unit of person equivalent (PE) [3]. A calculated positive value of normalized impact potential presents a contribution to the impact, and a negative one indicates an avoidance of the impact or resource consumption. Scenarios of municipal waste management system in Krakow Krakow city is inhabited by residents and a significant share of temporary residents, such as tourists and students. The average unit generation rate of municipal waste from households for Krakow city is kg per person per year. In 2010 the amount of residual waste generated in households was estimated at Mg, while from commercial activity it was Mg [8]. The residual waste from households in Krakow were analysed from November 2010 to October The results of the study [8] showed: water content 41.1%, volatile solids in dry matter 78.3%, lower heating value 7.93 MJ/kg, heat combustion 7.94 MJ/kg, Cl content in dry matter 0.297%, F content in dry matter % and S content in dry matter 0.168%. Selective collection systems are established for recyclables (paper, glass, metal, plastics), textiles, bulky waste, garden waste, construction and demolition waste, hazardous waste. Selectively collected recyclables are transferred to the sorting station, prior they are sent to recycling processes. Bulky waste is recovered at the dismantling station. Separately collected garden and park waste is subject to the biological treatment - composting process, made in 2 composting plants. Three scenarios for residual (non-separately collected) municipal waste management in Krakow are modelled employing EASETECH. Scenario A: under this scenario residual (non-separately collected) waste is transferred to be landfilled at the modern well equipped facility. Landfill gas is collected and subsequently converted into heat and electricity. Leachate is captured by drainage system then through sewerage reaches the municipal wastewater treatment plant. 4304

3 Scenario B: represents long-term plan for the municipal waste management system in Krakow. Under this scenario mixed waste is transferred to a thermal treatment plant with energy recovery, envisaged for Krakow municipality. The plant will start its operation in the second half of Scenario C: since 2013 landfilling has been replaced by mechanical biological treatment (MBT) of residual waste. The first step of the process is the separation of metals (magnetically) and glass (manually), then waste is screened in a rotary sieve (trommel). The fine fraction consists mostly of organic matter and undergoes aerobic biological treatment (stabilization) in composting reactors. The compost is low quality and it is sent to a landfill. The coarse fraction is split into the light fraction combustible refuse-derived fuel (RDF) and heavy fraction. RDF is then incinerated, the heavy fraction is sent to a landfill. Management of separately collected waste (recyclables, garden waste, bulky waste) is identical for three scenarios, therefore separately collected waste and its treatment is excluded from the system boundary. The collection and transportation of residual waste are assumed to be equal for all scenarios. The transport distance is also assumed to be the same, as the landfill, the incinerator and the mechanicalbiological treatment plant are located in Krakow, the distances to the city centre are similar. Results and discussion The environmental impacts of the three scenarios for residual waste management in Krakow: landfilling, incineration and mechanical biological treatment (MBT) were calculated with EASETECH model employing the EDIP 2003 methodology. The modelling was performed assuming the same quantity and quality of residual waste for three scenarios. The results of modelling were calculated as normalized potential impact, in the person equivalent (PE) unit, for 13 impact categories and were shown in Table 1. Table 1. Normalized environmental impact for landfilling, incineration and mechanical biological treatment (MBT) of residual waste in Krakow Impact category Unit Landfilling Incineration MBT Acidification PE 4.72E E E+03 Ecotoxicity acute in water PE 2.17E E E+01 Ecotoxicity chronic in soil PE 3.08E E E-01 Ecotoxicity chronic in water PE 3.98E E E+01 Eutrophication combined potential PE 2.86E E E+03 Eutrophication separate N potential PE 3.61E E E+03 Eutrophication separate P potential PE 3.72E E E+00 Terrestrial eutrophication PE -2.67E E E+03 Global warming GWP 100a PE 6.42E E E+03 Human toxicity via air PE 4.04E E E+03 Photochemical ozone formation, impacts on human health PE 2.20E E E+03 Photochemical ozone formation, impacts on vegetation PE 1.30E E E+03 Stratospheric ozone depletion, ODP total PE 2.03E E E+01 Source: authors own 4305

4 The results of modelling for three scenarios were compared to each other and presented in Fig. 4 and 5. PE 1,E+07 9,E+06 8,E+06 7,E+06 6,E+06 5,E+06 4,E+06 3,E+06 2,E+06 7,E+05-3,E+05 Incineration versus landfilling 2,E+08 3,E+07 4,E+08 3,E+13 4,E+13 4,E+11 6,E+13 4,E+13 2,E+14 1,E+14 2,E+09 Incineration Landfilling Fig. 4. Normalized impact of incineration versus landfilling of residual waste in Krakow. Source: authors own PE 1,E+04 8,E+03 6,E+03 4,E+03 2,E+03 0,E+00-2,E+03-4,E+03-6,E+03-8,E+03-1,E+04 Incineration versus mechanical biological treatment 4,E+05 6,E+057,E+05 4,E+05 3,E+058,E+056,E+05 Incineration MBT -3,E+05 Fig. 4. Normalized impact of incineration versus mechanical biological treatment (with incineration of the light fraction and landfilling of the stabilized organic fraction) of residual waste in Krakow. Source: authors own 4306

5 The environmental effect of incineration is much lower than the effect of landfilling, while the environmental effect of MBT (with landfilling of the stabilized fine organic fraction and heavy coarse fraction and combustion of the RDF) is lower than the effect of incineration. The most severe disparity in values is observed for global warming: for incineration and MBT the values are below zero (-2.70E+05PE for incineration, -8.20E+03 for MBT), while for landfilling it far exceeds zero (6.42E+13PE); it means the quantity of the difference between incineration and landfilling is 18 orders of magnitude. The values below zero for incineration and MBT indicate positive impact on the environment, which is mainly due to avoided emission of carbon dioxide of fossil origin. Incinerated wastes are the source of energy therefore less fossil fuels are burnt to produce energy (avoided emission). For all types of ecotoxicity impact categories, incineration values are below zero, while those for landfilling are significantly above zero, for MBT are slightly above zero. For eutrophication impact categories for incineration and landfilling values are above zero, however for incineration they are much lower (E+05 PE) than for landfilling (E+13PE), while values for MBT are below zero or near zero. The impact category human toxicity shows values above zero for incineration and landfilling, much higher in the case of the latter and value below zero for MBT. Concerning photochemical ozone formation, landfilling, incineration and MBT exhibit values above zero, the values for landfilling are much higher than for incineration and the lowest values are for MBT. Values for stratospheric ozone depletion categories are below zero for incineration (-3.86E+01), yet much above zero for landfilling (2.03E+09) and slightly above zero for MBT (2.19E+01). For the acidification impact category, values for incineration (4.72E+05) and landfilling (4.72E+05) are almost equal, while for MBT (-8.76E+03) the value is lower by 8 orders of magnitude. The lowest environmental impact is indicated for the MBT scenario. The most significant processes in this scenario are: landfilling of the stabilized organic fraction (poor quality compost), which has negative impact and combustion of the RDF, which has positive impact. Determinants affecting the results for landfilling are these, which influence landfill gas potential generation and its quantity, in particular the biodegradable waste content. Therefore the lowering of the organic content through biological stabilization of the fine fraction could entail minimizing the negative effect of the landfilling process. The results for combustion are affected significantly by the water content and the heating value. Lowering the water content and increasing the heating value through the separation processes of residual waste and producing the RDF could improve the environmental performance of municipal waste incineration. On the other hand for the mechanical processes (separation) and biological processes (stabilization/composting) the energy supply is needed, both fuel (for diesel engine machineries) and electricity. Still for modelling of the MBT scenario some uncertainties could be noticed, especially these related to energy and fuel consumption. Conclusions Results of modelling show that landfilling and incineration of residual waste impact negatively on the environment. However for incineration the negative impact is much lower than for landfilling. The lowest environmental impact is indicated for the mechanical biological treatment (MBT) scenario. The highest share in the negative effect for MBT scenario has landfilling of the stabilized organic fraction (poor quality compost). The process contributing mainly for positive effect is the RDF combustion. The Life Cycle Assessment (LCA) methodology is an effective management tool for identifying and assessing the environmental impacts and could be employed to choosing the waste management option, with the lowest negative effects on human health and the environment. Abstract Effectiveness and viability of the planned municipal waste management system depends strongly on the organisation of logistic processes within such a system. The superior objective of any waste management system should be to minimize the negative effects of waste on human health and the environ- 4307

6 ment. The preference of waste treatment technology should be based on a scientific method such as Life Cycle Assessment (LCA) methodology. The aim of this study is comparing three scenarios for residual municipal waste treatment in Krakow, with application of the Life Cycle Assessment methodology and indicating the scenario with the lowest negative impact on the environment and human health. Keywords: municipal waste, waste management system, life cycle assessment, modeling, landfilling, incineration, mechanical biological treatment Streszczenie WYBÓR SCENARIUSZA GOSPODARKI ODPADAMI KOMUNALNYMI Z ZASTOSOWANIEM METODYKI ANALIZY CYKLU ŻYCIA (LCA) Efektywność planowanego systemu gospodarki stałymi odpadami komunalnymi zależy w dużej mierze od sposobu zorganizowania procesów logistycznych w obrębie takiego systemu. Nadrzędnym celem każdego systemu gospodarki odpadami powinno być minimalizowanie negatywnego oddziaływania odpadów na zdrowie ludzi i środowisko przyrodnicze. Wybór technologii zagospodarowania odpadów powinien być oparty o naukowe podstawy takie jak np. metodyka analizy cyklu życia. Celem niniejszego opracowania jest porównanie trzech scenariuszy zagospodarowania zmieszanych odpadów komunalnych w Krakowie, z zastosowaniem metodyki analizy cyklu życia oraz wskazanie scenariusza o najmniejszym negatywnym oddziaływaniu na środowisko i zdrowie ludzi. Słowa kluczowe: systemu gospodarki stałymi odpadami komunalnymi, zagospodarowanie odpadów, analiza cyklu życia, modelowanie References [1] Bjorklund A., Finnveden G., Roth L.: Application of LCA in Waste Management. In: Solid Waste Technology & Management, Christensen Th. H. (Eds.), Blackwell Publishing Ltd., [2] Directive 2008/98/EC of the European Parliament and of the Council of 19 November 2008 on waste and repealing certain Directives (OJ L 312/3, ). [3] Hansen T.L., Christensen T.H., Schmidt S: Environmental modelling of use of treated organic waste on agricultural land: a comparison of existing models for life cycle assessment of waste systems. Waste Management & Resource No. 24/ [4] Kirkeby J.T., Birgisdottir H., Hansen T.L., Christensen T.H., Bhander G.S., Hauschild M.: Environmental assessment of solid waste systems and technologies: EASEWASTE. Waste Management Research, No. 24/ [5] Korzeń Z.: Ekologistyka, Biblioteka Logistyka, Poznań [6] Krzywda D.: Zadania dla logistyki w realizacji celów nowoczesnych systemów gospodarki odpadami komunalnymi. Logistyka No. 6 / [7] Krzywda D., Procesy logistyczne w gospodarce stałymi odpadami komunalnymi. Logistyka No. 2/2012. [8] Sieja L., Kalisz M., Książek D., Szojda G.: Badanie ilości i struktury odpadów komunalnych Miasta Krakowa. Raport końcowy, Instytut Ekologii Terenów Uprzemysłowionych, Katowice, [9] U.S. Environmental Protection Agency (EPA). Life Cycle Assessment: Principles and Practice. EPA/600/R-06/060. May

7 [10] UNEP/SETAC, Life Cycle Approaches - the Road from Analysis to Practice. Life Cycle Initiative, United Nations Environment Programme. Division of Technology, Industry and Economics, Paris, France 2005 [11] Ustawa z dnia 14 grudnia 2012 o odpadach (Dz.U poz. 21. z późn. zm) Acknowledgements The work was completed within the scope of AGH University of Science and Technology statutory research for the Faculty of Mining Surveying and Environmental Engineering No