Modelling of integrated solid waste management systems in an island

Modelling of integrated solid waste management systems in an island

Resources, Conservation and Recycling 41 (2004) 243–254 Modelling of integrated solid waste management systems in an island A. Skordilis∗ Ministry fo...

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Resources, Conservation and Recycling 41 (2004) 243–254

Modelling of integrated solid waste management systems in an island A. Skordilis∗ Ministry for the Environment, Physical Planning and Public Works, 147 Patission Street, GR-11251 Athens, Greece Received 24 January 2002; received in revised form 30 September 2003; accepted 31 October 2003

Abstract This paper presents a system’s engineering model for the strategic planning of an integrated solid waste management at local level and more specifically in an island with touristic development. The model was developed for the island of Corfu, but it can also be implemented in other touristic islands all over the world. It combines the worth benefit utility analysis (WBU) with the life cycle analysis (LCA), taking into account environmental, financial, technological and social criteria. The model’s implementation in the island of Corfu demonstrates that the most efficient method for the waste disposal in Corfu is the combination of the material sorting at the waste source and the production of compost from the organic fraction. © 2004 Elsevier B.V. All rights reserved. Keywords: Solid waste management systems; Material recycling centre; Composting plant; Sanitary landfill; Life cycle analysis (LCA); Worth benefit utility analysis (WBU); Local authorities responsibility

1. Introduction The problems derived from solid waste have a unique and complicated character; they are not only a potential source of pollution, but they can be used as a secondary source of raw materials. The selection of priorities regarding the solid waste management has direct economic and environmental impacts. This procedure concerns not only the environmental policy but also technological, economic and purchasing policies. It is obvious that the continuously increasing waste production must be effectively reduced in terms of produced quantities, environmental risks and all possible damages that ∗

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can be caused. The decision-makers are trying to find solutions that will satisfy both the environmental and economic criteria. For that purpose, they use models that evaluate all the alternative methods of waste disposal. However, such a model can never be an ultimate decision-making instrument and it is mostly used as an aid or/and as a complementary tool to other designing tools (Baetz, 1990). A series of models has been developed until now, such as the WRAP model, which defines facility locations and compacities for a region and is based on a mixed integer programming (Bez et al., 1998). On the basis of cost optimization, a dynamic model was developed by (Chang et al., 1996), while (Eggels and Van der Ven, 1995; Hokkanen et al., 1995) used multi-criteria methods off their attempt to design an adequate solid waste management system. Besides, the MWS model (Ljunggren, 2000) integrates cost minimization and emissions accounting and is intended for evaluating waste treatment technologies and waste management policies, both from financial and environmental point of view. Most of the existing models focus on technological, financial and environmental systems. There are only a few models that refer to policy issues, such as analysing social criteria (employment, social acceptance) and the environmental aspects of LCA use. The selection of the appropriate method is commonly based on a cost–benefit analysis rather than the worth benefit utility analysis (WBU), which is certainly a more complete method. However, it should be mentioned that most of the existing models have been developed with reference to one or two categories of waste while ignoring others such as house and hazardous waste and specific waste such as agricultural waste, end of life vehicles, etc. During the last year, local authorities have shown great interest on solid waste management (Hasit and Warmer, 1981). Acting on a national level, the governments implement several innovative policies for waste management in terms of sustainable development. Additionally, local authorities, which face numerous of financial, organizational problems and community acceptance, have the whole responsibility for the implementation of waste management systems (Ministry of the Environment, 2000). This article describes a new model for the design of an integrated waste management at local level, which integrates political, social, environmental, technological and financial parameters. The model’s implementation has been realised in a Greek island, Corfu. It can be successfully used by government agencies, local authorities, technical consultants, companies producing waste management technologies etc.

2. Material and methods The solid waste disposal can be characterized as a multi-input process. There have been developed several models concerning the estimation of impacts caused by the different disposal methods. The comparison of the different methods becomes even more difficult, since there is a non-linear relationship between the input fraction and the emissions of pollution (Nielsen and Hauschild, 1998). Another important step for the aforementioned procedure is the definition of the time period LCA needs to refer. This period varies between 15 and 500 years (Finveden and Huppes, 1995; Skordilis, 1989; Read, 1998; Rousseau et al., 1997; White et al., 2003). All the existing models regarding the waste management systems

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on a local level are based on either simulation (Finveden and Huppes, 1995) or linear programming (Hasit and Warmer, 1981). In the present study, the model combines the worth benefit utility analysis with the life cycle analysis (LCA). The WBU analysis evaluates a series of alternative solutions for the disposal of the wastes based on the appropriate criteria that have been prioritized according to the priorities of the various institutions. The comparison of the alternative solutions is not based only to solid impartial objective information but also on subjective information (opinions). That kind of information is explicitly used during the configuration of the targets of the prioritization of the decision-making persons. The basic stages of the planning (Fig. 1) require: (a) Collection of the data and their evaluation (policy, quantities, composition, market, technology, economic data, etc.). These data are collected and processed by experts using various methods such as input–output analysis, Delphi, development of scenarios, etc. (b) Determination of the targets and the structure of the system. The targets, from which the relevant criteria for the evaluation of the alternative solutions are deduced, are the necessary tools for the model of the decision-making process. Next, their plenitude and their classification in groups depending on their functional relations is examined. The designed structure of the targets lies in two levels and consists of four main targets and the secondary ones. It starts from the general description of the problem and ends up to the individual problems (Table 1). The stakeholders that determine the targets (ministries, local authorities, industry, professional chambers, banks, ecological groups, residents), expressed their different views and ideas in the form of different evaluation of the targets within the frame of the prioritization. For this reason, estimated values were given, e.g. quantities of waste (kg/day), emission concentrations (mg/m3 ) etc. so that the whole system becomes functional. The prioritization of the targets was expressed in quantitative values. (c) The evaluation of the alternative solutions. According to the WBU the classification of the alternative solutions has to fulfil the following conditions: 0.1. Completeness; 0.2. Domination of the individual classification of the priorities; 0.3. No arbitrariness of individual classification. The first step of the evaluation was the rating of the contribution of each alternative solution. Every expert rated the functional relation of the characteristics of every alternative solution and its corresponding targets. The grades ranged from 1 to 10. The arithmetic mean was used as an average value of the evaluation. The individual values of the targets that resulted from this rating procedure were multiplied by the value of each target. These individual values of each alternative solution were added and result in the general value of each alternative. In order to have an estimation of the danger that every decision carries, it was necessary to draw the boundaries of the field of the possible degree of fulfilment and next to examine with more than one values of the targets per criterion. With this analysis (sensitivity analysis) we can picture the impacts caused by a small change of the main parameters.

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Fig. 1. Management model.


The best process of waste disposal 1. Improved implementation of environmental policy 1.1. Increase of social acceptance 1.2. Increase of environmental policy implementation 1.3. Improved use and implementation of environmental legislation 1.4. Unemployment reduction

2. Reduced ecological impacts 2.1. Reduced air pollution 2.2. Reduced water pollution 2.3. Reduced land contamination

2.4. Reduced risks 2.5. Reduced noise pollution 2.6. Reduced odours 2.7. Better view

3. Economic development 3.1. Reduced investment and operational costs 3.2. Improved financial development in other sectors 3.3. Increased revenues

3.4. Consumption increase 3.5. Improved advantage out of funding 3.6. Reduced land value

4. Better technology implementation 4.1. Better operational system 4.2. Improved technological system 4.3. Increased security

4.4. Better adjustment to new demands 4.5. Longer life cycle 4.6. Fast plant construction 4.7. Improved plant’s credibility 4.8. Less demands on expert staff

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Table 1 Structure of the criteria system



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The life cycle analysis was used for the targets of the environmental impacts and was carried out according to ISO 14040. The structure of the LCA comprises the monitoring of the life cycle of the methods, their interpretation (classification, characterization, normalization, sensitivity analysis) and the conclusions.

3. CASE study of Corfu island The application of this model is illustrated in the case study of the solid waste management system of Corfu island. The study was set up in cooperation with a group of experts on waste from Corfu Union Of Environment and Cleaning. The union has the entire responsibility for the waste management in the island. In the case of Corfu, the complete design aims at a dynamic, common and long lasting solid waste management in accordance with the European Community’s legislation. Generally, the waste management policy includes four parts: (a) (b) (c) (d)

The prevention of waste production. The recycling and reuse of useful waste materials. The controlled disposal of non-recyclable residues and. The rehabilitation of unauthorized landfills.

3.1. Area description The study is based on a reference case for the year 1999 and another one for the year 2011. Corfu is situated at the North–West side of the country and it covers 641 m2 of land with population of 110,000 habitants. The geomorphology of the island can be characterized as hilly, semi-mountaineer with many small valleys. This island belongs to the external part of the Ionian geotectonic zone. The geological formations mainly consist of limestone. The climate of Corfu is mild mediterranean. The total annual rainfall comes up to 1100 mm. The temperature does not present significant variabilities (the annual average is 17.46 ◦ C). The gross regional product is shared out to the primary sector (21%), the secondary sector (13%) and mainly the tertiary sector (66%). The prefecture is constituted of 13 municipalities and three communities. The Corfu island is geographically divided in three parts. The mountainous area (with a highest peak of 914.0 m) is situated at the north side of the island. The central part of the island is hilly and presents rich vegetation, while the south part is flat. As it concerns the biota, there are numerous kinds such as Limonium armtum, Stachus mollisina, Triturus cistatus, etc. In general terms, the development of Corfu can be characterized as agricultural as far as it concerns the land use, since the 54.42% of the land is covered with cultivations and especially olive trees. The 23.29% of the land is rangeland, the 5.19% is covered by forests, the 2.3% is water and the 14.8% is being used for other activities. The tourism is significantly developed in the island. It is estimated that annual overnight residences in Corfu will exceed the 13,500,000 by the year 2011.

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In 1999, the annual waste production was 50,000 t. In 2011, this number is estimated to reach 82,000 t. The composition of waste is defined as follows: • • • • • • • •

Organics: 45.0% Paper: 22% Glass: 4.0% Plastics: 11.0% Metals: 4.5% Leather, wood, rubber: 5.0% Inerts: 3.0% Others: 5.5%

The collection of MSW takes place four to five times per week. The MSW disposal is being realised into 19 different sanitary landfills. The 18 of the existing landfills do not work in accordance with the legal sanitary landfill specifications.

Fig. 2. Alternative solution A1.


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4. The alternatives and the structure of the criteria system The waste treatment and disposal alternatives that were examined are being presented herewith: 1. Sorting at source + material recycling center + composting plant + sanitary landfill (Fig. 2).

Fig. 3. Alternative solution A2.

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2. Sorting at source + material recycling center + thermal treatment including energy recovery + sanitary landfill (Fig. 3). The structure of the criteria system is as follows: • one general target, which concerns “the best process of waste disposal”. The four main targets are: 1. 2. 3. 4.

“improved implementation of the environmental policy”; “reduced ecological impacts”; “financial improvement”; “improved technological implementation”.

The aforementioned four main targets are being developed in 25 secondary ones (Table 1). The evaluation and scale of targets was realised by a team of seven individuals working in different sectors (ministries, local authorities, ecological associations, industry, professional chambers, banks and residents). A total of 40 evaluations were conducted by seven representatives. The largest identification of opinions was for targets “increase of environmental policy implementation”, 2.2 “reduced air pollution” and 3.1 “reduced investment and operational costs”. A group of four persons investigated possible interrelations of the elements in the system using the method of pair comparison. The results showed that the target 4.4 “better adjustment to new demands” gets a “bonus” of 20% and the target 4.1 “better operational implementation” a “malus” of 14%. The different subparts of each target and each alternative solution are presented in Figs. 4–7. Fig. 8 presents the graph of all main targets. The estimated values of the targets were multiplied by the coefficient of fulfilment of each alternative solution. The total represents the classification. The results, even after the sensitivity analysis, demonstrate that the first alternative solution is better than the second one, which includes the incineration of residues.

Fig. 4. Evaluation of the criteria for “better implementation of the environmental policy”.


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Fig. 5. Evaluation of the criteria for “reduced ecological impacts”.

Fig. 6. Evaluation of financial criteria.

Fig. 7. Evaluation of technological criteria.

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Fig. 8. Graph of all the main targets.

5. Conclusions It is obvious that the different tools, which have been developed within the last few years (e.g. LCA), help the evaluation of multi-criteria analysis such as WBU. In this way, the designing decisions become more comprehensible by the citizens, who finally accept them positively. This is achieved by the integration of social parameters into the financial, environment and technological parameters. The advantage of the evaluation with the method of worth benefit utility analysis is that, in contrast with the cost–benefit analysis the criteria of the environmental policy are also included (compliance with the legislative settings, social acceptance, labour). Its disadvantage is the subjectivity of the persons who evaluate. However, by employing a group of persons with different priorities in conjunction with the sensitivity analysis this disadvantage is minimized. The case study of the integrated waste management system in a touristic island, such as Corfu, is a representative example of the proper use of a simplified model with the latest developed tools of environmental management systems. The results have demonstrated that the combination of material recovery at the source with the utilization of the organic fraction is the optimum solution for small local communities.

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