ESTIMATION OF MUNICIPAL SOLID WASTE HEATING VALUE IN GREECE IN THE FRAME OF FORMULATING APPROPRIATE SCENARIOS ON WASTE TREATMENT I.-S. Antonopoulos*, A. Karagiannidis*, E. Kalogirou** * Aristotle University, Departement of Mechanical Engineer, Laboratory of Heat Transfer and Environmental Engineer, GR 54124, Box 483, Thessaloniki, Greece ** Waste to Energy Research and Technology Council, Greece Abstract Prevention of waste production at source, recycling of packaging waste and processing the organics are the main parts of the Hellenic waste management strategy. In the meanwhile recycling of packaging wastes may be compatible with incineration within integrated waste management systems. In order to estimate and calculate the energy potential of the Municipal Solid Wastes a mathematical model was structured taking into consideration the existing legislation and infrastructure on waste management plants and their residuals. Initial goal of this paper was the formulation of an appropriate model for forecasting the waste generation till 2030 taken into account the restrictions of the Landfill Directive 1999/31/EC. Afterwards, the recycling impact and the organic waste diversion in the heating value of the MSW were investigated. ΑΝΑΠΤΥΞΗ ΟΛΟΚΛΗΡΩΜΕΝΗΣ ΜΕΘΟ ΟΛΟΓΙΑΣ ΥΠΟΛΟΓΙΣΜΟΥ ΕΝΕΡΓΕΙΑΚΟΥ ΠΕΡΙΕΧΟΜΕΝΟΥ ΥΠΟΛΕΙΜΜΑΤΙΚΩΝ ΑΣΤΙΚΩΝ ΣΤΕΡΕΩΝ ΑΠΟΒΛΗΤΩΝ ΚΑΙ ΥΠΟΛΕΙΜΜΑΤΩΝ ΑΠΟ ΜΟΝΑ ΕΣ ΕΠΕΞΕΡΓΑΣΙΑΣ ΤΟΥΣ I.-Σ. Αντωνόπουλος*, Α. Καραγιαννίδης*, Ε. Καλογήρου** * Αριστοτέλειο Πανεπιστήµιο Θεσσαλονίκης, Τµήµα Μηχανολόγων Μηχανικών, Εργαστήριο Μετάδοσης Θερµότητας και Περιβαλλοντικής Μηχανικής, Τ.Κ. 54124, Θυρίδα 483, Θεσσαλονίκη ** Συµβούλιο Ενεργειακής Αξιοποίησης Αποβλήτων Περίληψη Η παρούσα εργασία αναφέρεται στο πρόβληµα της διαχείρισης των Αστικών Στερεών Αποβλήτων (ΑΣΑ) στην Ελλάδα, επισηµαίνοντας τις απαιτήσεις και τις κατευθύνσεις που δηµιουργούνται µέσα από την εφαρµογή των κοινοτικών οδηγιών, παρουσιάζοντας τις βασικές τεχνολογίες επεξεργασίας και αξιοποίησης των ΑΣΑ. Στόχος της εργασίας είναι η ανάπτυξη κατάλληλων σεναρίων παραγωγής και διαχείρισης ΑΣΑ, ώστε να προσδιοριστεί πλήρως το ενεργειακό περιεχόµενο των υπολειµµάτων από κάθε επεξεργασία για περαιτέρω ενεργειακή πλέον αξιοποίηση. Η αποτύπωση των στόχων µιας τεχνολογίας µηχανικής επεξεργασίας και αξιοποίησης ΑΣΑ, η δυνατότητα κάλυψης των απαιτήσεων της κείµενης νοµοθεσίας και η αξιοποίηση των προϊόντων της, αποτελούν τις κοµβικές παραµέτρους για την ορθολογική ανάπτυξη και εφαρµογή ενός βιώσιµου Συστήµατος Ολοκληρωµένης ιαχείρισης ΑΣΑ. Αξίζει να επισηµανθεί ότι το θέµα της επιλογής της κατάλληλης µεθόδου επεξεργασίας και αξιοποίησης ΑΣΑ, είναι ένα σύνθετο και περίπλοκο ζήτηµα ή πρόβληµα, στο οποίο απαιτείται να συναξιολογηθούν µια σειρά από τεχνικό-οικονοµικές, περιβαλλοντικές και κοινωνικές παραµέτρους.
1. INTRODUCTION In EU-27, 524 kg of Municipal Solid Waste (MSW) was generated per capita in 2008. Of the total amount of MSW in EU-27, 40% was landfilled, 20% incinerated, 23% recycled and 17% composted [1]. In Greece in the year 2000, aprroximately 4.6 million tons of MSW was generated, which is an increase of 50% compared to 1990 [2]. According to the Hellenic Technical Chamber [3], MSW in 2007 consisted of 40% organic material, 29% paper and cardboard, 14% plastic, 3% metal, 3% glass, 3% inert waste, 2% leather-wood-textiles and 6% other waste. In the same year, the collected recyclable materials were approximately 1050 kt, 38% of which were paper and cardboard, 28% plastics, 14% glass, 13% metals and 7% leather-wood-textiles. The main policy orientation in Greece is the maximization of material recovery through the implementation and extension of recycling programs with source separation in all the large municipalities, in addition to the construction of Material Recovery Facilities (MRF). Absolute priority is the remediation of the old open dumps and the construction of new sanitary landfills. Currently, 63 sanitary landfills exist, but only three of them are equipped with biogas system collection and flaring. Figure 1: MRF and MBT plants current status in Greece; in italics are the MBT plants which are planned to be constructed in accordance to table 1 and in bold are the MRF plants. The MBT plants location is referred to each region. Table 1: MBT plants current status in Greece, in combination with the map in Figure 1. According to the Directive 1999/31/EC considering waste landfilling, EU-countries are obliged to reduce the amount of landfilled Biodegradable Municipal Waste (BMW) to: i) 75% of the total amount of BMW generated in 1995 by 2010 (this target won t be achieved basing on the current situation and facts), ii) 50% of 1995 levels by 2013 and iii) 35% of 1995 levels by 2020. Moreover, the amendment of the Directive 2004/12/EC, 94/62/EC, obliges that no later than 31 December 2008, 60% by weight for glass, paper and cardboard, 50% for metals, 22.5% for plastics and 15% for wood should be recycled. Regarding to BMW management, currently 3 Mechanical Biological Treatment (MBT) plants operate in Greece (Liossia, Chania and Irakleio). Additionally it is scheduled to start two MBTs their operation, in Ditiki Elllada and the second in Peloponnisos in 2011. These 5 plants will have a total treatment capacity of 766.5 kt of residual MSW in 2011. Even though Regional Planning studies in Greece have proposed the construction of a new MBT or Waste-to-Energy (WtE) plants; at the moment (January 2011) plants seem to stall and if this situation remains no new plants are expected to operate before 2013. Considering packaging wastes, the legislative framework (set new recycling targets resulting into increase of recycling rates from 42.8% in 2006 to 44% in 2008 [1]. Figure 1 illustrates the location and the number of the MRF. In this paper a mathematical model is presented which calculates the MSW composition applying different recycling rates of packaging materials or different diversion rates of the organic waste in
order to identify the recycling impact in the heating value of the MSW. 2. METHODOLOGY 2.1. Model overview Figure 2 depicts an integrated waste management model taking into consideration the existing infrastructure in Greece. The described model combines the following attributes: i) separate collection at source, which depends on the mass fraction of each waste material, ii) recycling of packaging materials and paper/cardboard, iii) organic waste diversion and iv) potential incineration of residues from MRF and MBT plants. Expected outcome of this model is the calculation of the heating value of the residuals MSW. Index: Figure 2: Model overview. In order to calculate the whole waste management system, the first step was to model the existing recycling and organic waste treatment plants and formulate their mass balance. The main target of modeling MBT and MRF plants was to estimate the amount of the residues and their composition in order to estimate then their heating value. Then the second step was to calculate the heating value of i) the MSW and ii) the residuals from the MRF and the MBT plants through appropriate mathematical equations. Especially for the MBTs, the produced quantities of Solid Recovered Fuels (SRF) and Refuse Derived Fuels (RDF) were taken into account together with various scenarios on the technology of the MBT plats which are planned to be constructed in the next years according to the National Planning [4]. Model s function is based on the following equations: S S m = m + m + m [1] 2.2 Waste predictions l r c res mi φ i( i= c, r ) = + m [2] i= c, r S mr r S MBT m c msrf + mrdf + m + S MRF res m r m + mr I res res m res mr + mc = m [3] res c = [4] = [5] For the estimation of the amounts of MSW disposed to sanitary landfills and trace out all the waste flows until 2030, it was assumed that new waste treatment plants according to National Regional Planning will be constructed with sufficient capacity to treat all residual MSW in Greece in order to diverse BMW from landfills and the targets of the Directive 1999/31/EC achieved. Moreover, it was assumed that recycling rate of packaging waste will increase gradually by 2011 in order to meet the revised targets of the Packaging Waste Directive (2004/12/EC), namely 55% w/w recycling of packaging waste and from then onwards packaging waste recycling will increase gradually every year. As far as other than packaging
waste materials, it was assumed that recycling rate will increase gradually until 2030. Figure 3 depicts the MSW Management in Greece until 2030, according to proposed model and aforementioned assumptions, taking into consideration a constant waste growth rate 1.1%, whilst figure 4 illustrates the BMW production and diversion that are described from the Directive 1999/31/EC. 1000 kt 8 7 6 Landfill Recycling MBT installed Gap? 8,00 (kt) 6,00 MSW production BMW production BMW disposal 5 4 3 2 1 0 2008 2009 2010 2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025 2026 2027 2028 2029 2030 Figure 3: Predictions on waste management treatment methods. 2.3 Modelling of waste management plants 4,00 2,00 0,00 2008 2010 2012 2014 2016 2018 Figure 4: BMW disposal and diverted quantities according to Directive 1999/31/EC. 2020 2022 2024 2026 2028 2030 2.3.1 MRF modelling In order to calculate the final residues from the MSW and the recovered materials it was necessary to model the sorting process, which takes place in sorting plants. Figure 5 illustrates the total mass balance of a sorting plant on a Life Cycle Analysis (LCA) approach taking into consideration the operation of these plants in Greece. For instance residuals are approximately 30% of the inserted waste with a mixed composition of organics, inert, light plastics fractions and paper/cardboard. 2.3.2. MBT modelling MBT reduces the mass and volume of wastes, due to the removal of recyclable materials and both carbon and moisture losses. The amount of reduction is very dependent on the design and technical characteristics of each plant (composting process or biodrying). MBTs which are equipped with biodry technology produce SRF, while composting plants produce RDF. Figure 6 illustrates the total mass balance for a composting plant (left figure) and biodrying plant (right figure) including RDF and SRF quantities, residuals and compost respectively. In case the proposed MBT plants indicated in Table 1 will be constructed, the total potential RDF/SRF quantities are those illustrated in figure 7 considering the installed technology on these plants. Figure 6: MBT input/output modelling [5,6].
900 Quantities (kt) 600 300 RDF SRF 0 Composting process-rdf production Biodrying process-srf production Figure 7: RDF and SRF quantities considering that scheduled MBT plants will be constructed taking into consideration the two scenarios: i) MBT plants with composting process and ii) MBT plants with biodrying process. Figure 5: MRF Input/Output modelling. 2.4 Heating value calculations An interesting option in waste management and energy recovery is the MSW incineration. Apart from the produced energy, thermal process also reduces MSW mass by as much as 70% and MSW volume by up to 85%. Higher Heating Value (HHV) and Lower Heating Value (LHV) are important knowledge for judging it s worth using waste as fuel. In practice, the HHV of a solid mixture, candidate to use as fuel in a thermal process, is determined by a calorimetric test bombing. On the other hand, it is possible to calculate HHV and/or LHV by using appropriate mathematical equations which are based on the chemical parameters of the waste in a wet or in dry basis respectively [7]. Table 2 illustrates the results of using each of the aforementioned equations compared by experimental results bringing the most accurate mathematical form. LHV is calculated by using appropriate mathematical forms or by subtracting from HHV the moisture together with the hydrogen contents. In this study, Dulong equation was used to dertermine the HHV and LHV was calculated by subtracting the moisture and hydrogen contents from each waste fraction (equation 1 and 2). Table 3 summarizes the chemical waste composition in a dry basis and the HHV and LHV for each waste fraction and table 4 illustrates the physical waste composition in combination with the LHV and HHV. Table 2: MSW HHV calculation using published mathematical forms; in italics are depicted the most accurate results compared with experimental results. Waste fraction Lloyd and Davenport De Boie Wilson Dulong Experimental Paper/cardboard 17.41 16.44 15.33 14.81 15.8 Food waste 6.44 6.11 5.81 5.57 5.51 Plastic 27.16 26.4 26.37 25.77 32.56 Textile 22.33 21.48 20.77 20.14 17.24 Rubber 27.15 26.81 27.25 26.77 25.33 Leather 38.59 38.4 40.14 39.69 36.24 Glass 0.26 0.25 0.25 0.24 0.14 Metal 1.88 1.76 1.63 1.55 0.7 Yard waste 8.37 7.93 7.46 7.14 6.51 3. RESULTS AND DISCUSSION In order to examine the influence of the diversion rates on the heating values of the MSW it is a prerequisite to calculate/estimate the physical MSW composition. The effect of varying the recycling and diversion rates of all the waste fractions simultaneously is displayed in figure 8. The recycling of paper packaging reduces the LHV of the residual waste but only 14% (when recycling rate is 100%). Although the plastic packaging percentage in the MSW composition
is much smaller than that of paper packaging (see table 4), the recycling impact in LHV is much more (about 60% reduction of the LHV). Table 2: Chemical waste composition, HHV and LHV values in a dry basis. Waste fraction Content (%) (ΜJ/kg) Moisture Carbon Hydrogen Oxygen Nitrogen Sulfur Ash HHV LHV Paper/cardboard 70 48 6,4 37,6 2,6 0,4 5 7,08 3,96 Food waste 6 43,5 6 44 0,3 0,2 6 14,49 13,03 Plastic 2 60 7,2 22,8 0 0 10 26,11 24,48 Textile 10 55 6,6 31,2 4,6 0,2 2,5 20,17 18,47 Wood waste 20 49,5 6 31,2 4,6 0,2 2,5 15,96 14,16 Yard waste 60 47,8 6 38 3,4 0,3 4,5 7,94 5,16 Glass 2 0,5 0,1 0,4 0,1 0 98,9 0,23 0,16 Metal 3 4,5 0,6 4,3 0,1 0 90,5 1,55 1,35 Other 20,5 20,91 2,39 12,78 0,4 0,1 42,93 6,72 5,69 Table 4: Waste Heating Value and physical waste composition. Waste fraction Composition (%) HHV (MJ/Kg) LHV (MJ/Kg) Organics 40 3.00 1.82 Paper/cardboard 29 4.20 3.78 Plastic 14 3.66 3.43 Glass 3 0.01 0.00 Metal 3 0.05 0.04 Leather-Wood-Textile 2 0.36 0.33 Inert 3 0.01 0.00 Other 6 0.40 0.34 Total 11.69 9.75 The separate collection of biodegradable waste and packaging materials has a strong negative impact on the LHV of the residual waste because of the high moisture content. On the opposite, the diversion of the biodegradable waste has a positive impact on the LHV of the residual waste due to the low moisture content in that fraction. Figure 8: MSW heating value applying different diversion rates and recycling rates in biodegradable and packaging waste respectively. Figure 9: BMW diversion in combination with LHV and targets set by 1999/31/EC. Figure 10: Packaging materials recycled in combination with LHV and targets set by 2004/12/EC.
As far as MBT and MRF residuals heating values are concerned, figures 11 and 12 illustrate the aforementioned comparison, taking into account two different scenarios depending on the MBT technology; whether the new MBTs have composting or biodrying technology. SRF can be distinguished from RDF in the fact that it is produced to reach an international standard (CEN/343 ANAS) and its heating value is estimated around 15 MJ/kg, whilst RDF heating s value is 18 MJ/kg [8]. As it was previously stated in 2.3.1 and 2.3.2, MRF residuals are approximately 30% of the inserted waste and its heating value is estimated to be about 5MJ/kg whereas MBT residuals which are consisted of mixed plastics, paper, organics and inert waste in a percentage of 15% of the inserted waste, with a heating value of 10.5 MJ/kg. Considering MBT residuals, when residual paper and light plastics fractions cannot establish a suitable RDF, then these fractions will be landfilled, increasing residual s heating value. Only a small account of the BMW content of the input waste is reduced in the biodrying process (less than with alternative composting processes that seek to fully biostabilise the waste). This is not an issue when the SRF is utilised as a fuel, but it would be if the SRF had to be landfilled or used in a WtE plant together with the residuals of the plant. Figure 11: Heating value of SRF/RDF and residuals from MBT and MRF plants; Case I: MBTs with biodrying technology. Figure 12: Heating value of SRF/RDF and residuals from MBT and MRF plants; Case II: MBTs with composting technology. In addition to the aforementioned results, a supplementary valorisation of the produced SRF/RDF took place by using the Tanner graphic method (figure 13). Figure 13: Tanner charts on the current Hellenic RDF/SRF: average content of RDF/SRF physicalchemical parameters. With blue line is depicted the self sustainable combustion area blue line, red line RDF, green line SRF. 5. CONCLUSIONS In Greece about 85% of the generated MSW is disposed of in landfills or in open dumps
which are still open in some municipalities. Landfill Directive 1999/31/EC demands the reduction of the biodegradable waste fraction which is sent to landfills, meaning that a national strategy on waste management should be followed. By implementing the aforementioned Directive, food waste will be diverted from the mixed waste stream, increasing the LHV of the residual waste and as a result increasing its potential use as a supplementary fuel in WtE plants or in existing industries such as cement industry etc. Recycling of packaging materials has a negative impact on LHV, but this will be compensated with the recovery of food waste and the recycling of the glass and metals. The aforementioned compensation will then increase the LHV of the residual waste. On the other hand, construction barriers of WtE plants exist in Greece; the main problem is due to political conflicts and/or high bureaucracy. In addition, the RDF/SRF market is very sensitive and flexible and its dependence from the low gate fees of the sanitary landfills creates barriers in the development of WtE practices and plants.concluding, the landfill Directive sets crucial restrictions regarding waste management for the next years. A national strategy should be carried beginning from the implementation of regional planning (constructing of waste management plants), combining recycling and food waste recovery implementing the international WtE practices in order to structure an integrated waste management system. ABBREVIATIONS BMW Biodegradable Municipal Waste MRF Material Recycling Facility HHV Higher Heating Value MSW Municipal Solid Waste LCA Life Cycle Analysis RDF Refuse Derived Fuel LHV Lower Heating Value SRF Solid Recovered Fuel MBT Mechanical Biological Treatment WtE Waste-to-Energy REFERENCES 1. Eurostat (2010). Environemt in the EU-27. Half a ton of municipal waste generated per person in the EU27 in 2007. Eurostat news release, 43/2010. 2. Papachristou E., Hadjianghelou H., Darakas E., Alivanis K., Belou A., Ioannidou D., Paraskevopoulou E., Poulios K., Koukourikou A., Kosmidou N. and Sortikos K. (2009). Perspectives for integrated municipal solid waste management in Thessaloniki, Greece. Waste Management, 29, 1158-1162. 3. TEE (2006). Solid Waste Management in Greece: Attica case. Hellenic Technical Chamber, November. 4. YPECHODE (2007). Anex II «Accounting and estimating needs on Waste Management plants», Corporate Programme Environment. 5. Scoullos M., Siskos P., Zeri C., Skordilis A., Ziogas Ch., Sakellari A., Giannopoulou K., Tsiolis P., Mavroudeas S., Argyropoulos I., Roumeliotis Th. and Skiadi O., (2009). Composition and chemical properties of RDF product at a MSW mechanical separation plant in Greece. Conference on thermal processing of MSW, National Technical Univesity of Athens. 6. Juniper (2005). Technology and Business Review MBT: Mechanical-Biological Treatment: A guide for decision makers, processes, policies and markets. Annex D, Process review G-J, Juniper Consultancy Services Ltd. 7. Meraz L., Domínguez A., Kornhauser I. and Rojas F. (2003). A thermochemical conceptbased equation to estimate waste combustion enthalpy from elemental composition. Fuel, 82, 1499-1507. 8. CEN/TC 343. Technical Committee on Solid Recovered Fuels.