Transshipment site selection using the AHP and TOPSIS approaches under fuzzy environment

Site selection is an important issue in waste management. Selection of the appropriate solid waste site requires consideration of multiple alternative solutions and evaluation criteria because of system complexity. Evaluation procedures involve several objectives, and it is often necessary to compromise among possibly conflicting tangible and intangible factors. For these reasons, multiple criteria decision-making (MCDM) has been found to be a useful approach to solve this kind of problem. Different MCDM models have been applied to solve this problem. But most of them are basically mathematical and ignore qualitative and often subjective considerations. It is easier for a decision-maker to describe a value for an alternative by using linguistic terms. In the fuzzy-based method, the rating of each alternative is described using linguistic terms, which can also be expressed as triangular fuzzy numbers. Furthermore, there have not been any studies focused on the site selection in waste management using both fuzzy TOPSIS (technique for order preference by similarity to ideal solution) and AHP (analytical hierarchy process) techniques. In this paper, a fuzzy TOPSIS based methodology is applied to solve the solid waste transshipment site selection problem in Istanbul, Turkey. The criteria weights are calculated by using the AHP.     

The choice of a solid waste management system using the Electre II decision-aid method

A multicriteria decision-aid method, Electre II, was applied to the real choice process of a solid waste management system in the Uusimaa region, Finland. The criteria used were chosen by a supervision group. The weights of the criteria were defined by the managers of environmental and technical affairs of each municipality in Uusimaa, Finland. The use of the Electre II method leads us to recommend centralized incineration as the best municipal solid waste management system for the planning region. However, the second best alternative, intermediate RDF combustion with intermediate landfilling was finally chosen by the municipalities.     

Flow analysis of metals in a municipal solid waste management system

This study aimed to identify the metal flow in a municipal solid waste (MSW) management system. Outputs of a resource recovery facility, refuse derived fuel (RDF) production facility, carbonization facility, plastics liquefaction facility, composting facility, and bio-gasification facility were analyzed for metal content and leaching concentration. In terms of metal content, bulky and incombustible waste had the highest values. Char from a carbonization facility, which treats household waste, had a higher metal content than MSW incinerator bottom ash. A leaching test revealed that Cd and Pb in char and Pb in RDF production residue exceeded the Japanese regulatory criteria for landfilling, so special attention should be paid to final disposal of these substances. By multiplying metal content and the generation rate of outputs, the metal content of input waste to each facility was estimated. For most metals except Cr, the total contribution ratio of paper/textile/plastics, bulky waste, and incombustible waste was over 80%. Approximately 30% of Cr originated from plastic packaging. Finally, several MSW management scenarios showed that most metals are transferred to landfills and the leaching potential of metals to the environment is quite small.     

Combustion kinetics of sewage sludge and combustible wastes

This study estimated the kinetics of the mono- and co-combustion of sewage sludge pellets and combustible wastes such as municipal solid waste (MSW) and refuse-derived fuel (RDF). Sewage sludge was manufactured into pellets with a diameter of 8, 12, or 16 mm and a length of 30 mm. The RDF was composed of paper and plastics and was formed into pellets with a diameter of 8 mm and a length of 30 mm. MSW samples were synthesized using combustible wastes such as garbage, paper, plastics, and wood. The MSW was adjusted to have a moisture content of around 40% after shredding to under 10 mm. A laboratory-scale batch type stoker incinerator was used for the combustion and the gas composition of the flue gas was measured. The activation energy was calculated using the experimental results, and then the relation of the decomposition rate and reaction time was evaluated using the shrinking core model. The decomposition rate of the sludge pellets decreased as their diameter and moisture content increased, and the co-combustion of sludge pellets and combustible waste was affected by the amount of combustible waste. The individual combustion rates of the cylindrical sludge pellets or RDF were mainly controlled by the chemical reaction, but in the case of shredded MSW it was mostly influenced by gas diffusion. The rate for the co-combustion of sludge pellets and combustible wastes was mainly determined by the combustion rate of the combustible waste. The activation energy of the 8-mm-diameter sludge pellets was between 6.70 and 10.0 kcal/mol, according to the moisture content, but it was lower for MSW and RDF. In the case of MSW co-combustion, the reaction rate accelerated as the moisture content of the sludge pellets decreased, but it was markedly increased by the addition of RDF, regardless of the sludge moisture content.     

Prediction of syngas quality for two-stage gasification of selected waste feedstocks

This paper compares the syngas produced from methane with the syngas obtained from the gasification, in a two-stage reactor, of various waste feedstocks. The syngas composition and the gasification conditions were simulated using a simple thermodynamic model. The waste feedstocks considered are: landfill gas, waste oil, municipal solid waste (MSW) typical of a low-income country, the same MSW blended with landfill gas, refuse derived fuel (RDF) made from the same MSW, the same RDF blended with waste oil and a MSW typical of a high-income country. Energy content, the sum of H2 and CO gas percentages, and the ratio of H2 to CO are considered as measures of syngas quality. The simulation shows that landfill gas gives the best results in terms of both H2+CO and H2/CO, and that the MSW of low-income countries can be expected to provide inferior syngas on all three quality measures. Co-gasification of the MSW from low-income countries with landfill gas, and the mixture of waste oil with RDF from low-income MSW are considered as options to improve gas quality.     

Wasteful waste-reducing policies? The impact of waste reduction policy instruments on collection and processing costs of municipal solid waste

We study the impact of some local policies aimed at municipal solid waste (MSW) reduction on the cost efficiency of MSW collection and disposal. We explicitly account for differences between municipalities in background conditions by using a bootstrapped version of the Data Envelopment Analysis methodology in combination with a matching technique. Using data on 299 municipalities in Flanders, Belgium, for the year 2003, our results indicate that municipalities that are member of a waste collection joint venture, or that subscribe to a voluntary agreement to reduce MSW at the highest ambition level, collect and process MSW more efficiently than other municipalities. Weekly instead of two-weekly waste collection, or using a weight-based pricing system appears to have no impact on efficiency. Our results show that aiming at MSW reduction does not lead to lower efficiency of public service provision, even on the contrary.     

Development of a purpose built landfill system for the control of methane emissions from municipal solid waste

In the present paper, a new system of purpose built landfill (PBLF) has been proposed for the control of methane emissions from municipal solid waste (MSW), by considering all favourable conditions for improved methane generation in tropical climates. Based on certain theoretical considerations multivariate functional models (MFMs) are developed to estimate methane mitigation and energy generating potential of the proposed system. Comparison was made between the existing waste management system and proposed PBLF system. It has been found that the proposed methodology not only controlled methane emissions to the atmosphere but also could yield considerable energy in terms of landfill gas (LFG). Economic feasibility of the proposed system has been tested by comparing unit cost of waste disposal in conventional as well as PBLF systems. In a case study of MSW management in Mumbai (INDIA), it was found that the unit cost of waste disposal with PBLF system is seven times lesser than that of the conventional waste management system. The proposed system showed promising energy generation potential with production of methane worth of Rs. 244 millions/y ($5.2 million/y). Thus, the new waste management methodology could give an adaptable solution for the conflict between development, environmental degradation and natural resources depletion.     

Using an innovative criteria weighting tool for stakeholders involvement to rank MSW facility sites with the AHP

The main aim of this study was to verify the efficacy of using an innovative criteria weighting tool (the “priority scale”) for stakeholders involvement to rank a list of suitable municipal solid waste (MSW) facility sites with the multi-criteria decision-making (MCDM) technique known as analytic hierarchy process (AHP). One of the main objectives of the study was to verify the behaviour of the “priority scale” with both technical and non-technical decision-makers. All over the world, the siting of MSW treatment or disposal plants is a complex process involving politicians, technicians as well as citizens, where stakeholders who are not effectively involved strongly oppose (or even obstruct) the realization of new facilities. In this study, in order to pursue both the technical (select the best site) and social aims (all the stakeholders have to give their aware contribution), the use of the “priority scale” is suggested as a tool to easily collect non-contradictory criteria preferences by the various decision-makers. Every decision-maker filled in “priority scale”, which was subsequently uploaded in the AHP tool in order to indirectly calculate the individual priority of alternatives given by each stakeholder (not using group aggregation techniques). The proposed method was applied to the siting of a composting plant in an area suffering from a serious MSW emergency, which has lasted for over 15 years, in the Campania Region, in Southern Italy. The best site (the “first choice”) was taken as the one that appeared the most times at the first place of each decision-maker ranking list. The involved technical and non-technical decision-makers showed the same behaviour in (indirectly) selecting the best site as well as in terms of the most appraised criteria (“absence of areas of the highest value for natural habitats and species of plants and animals”). Moreover, they showed the same AHP inconsistency ratio as well as the same behaviour in comparison with a “balanced decision-maker” (who assigns identical weights to all the considered criteria). Therefore, the proposed criteria weighting tool could be widely as well as easily used for stakeholders involvement to rank MSW facility sites (or other kinds of alternatives) with the AHP or with other MCDM techniques, taking or not into consideration group aggregation methods.     

CCA-treated wood disposed in landfills and life-cycle trade-offs with waste-to-energy and MSW landfill disposal

Chromated copper arsenate (CCA)-treated wood is a preservative treated wood construction product that grew in use in the 1970s for both residential and industrial applications. Although some countries have banned the use of the product for some applications, others have not, and the product continues to enter the waste stream from construction, demolition and remodeling projects. CCA-treated wood as a solid waste is managed in various ways throughout the world. In the US, CCA-treated wood is disposed primarily within landfills; however some of the wood is combusted in waste-to-energy (WTE) facilities. In other countries, the predominant disposal option for wood, sometimes including CCA-treated wood, is combustion for the production of energy. This paper presents an estimate of the quantity of CCA-treated wood entering the disposal stream in the US, as well as an examination of the trade-offs between landfilling and WTE combustion of CCA-treated wood through a life-cycle assessment and decision support tool (MSW DST). Based upon production statistics, the estimated life span and the phaseout of CCA-treated wood, recent disposal projections estimate the peak US disposal rate to occur in 2008, at 9.7 million m(3). CCA-treated wood, when disposed with construction and demolition (C&D) debris and municipal solid waste (MSW), has been found to increase arsenic and chromium concentrations in leachate. For this reason, and because MSW landfills are lined, MSW landfills have been recommended as a preferred disposal option over unlined C&D debris landfills. Between landfilling and WTE for the same mass of CCA-treated wood, WTE is more expensive (nearly twice the cost), but when operated in accordance with US Environmental Protection Agency (US EPA) regulations, it produces energy and does not emit fossil carbon emissions. If the wood is managed via WTE, less landfill area is required, which could be an influential trade-off in some countries. Although metals are concentrated in the ash in the WTE scenario, the MSW landfill scenario releases a greater amount of arsenic from leachate in a more dilute form. The WTE scenario releases more chromium from the ash on an annual basis. The WTE facility and subsequent ash disposal greatly concentrates the chromium, often oxidizing it to the more toxic and mobile Cr(VI) form. Elevated arsenic and chromium concentrations in the ash leachate may increase leachate management costs.     

Combustion characteristics of Malaysian municipal solid waste and predictions of air flow in a rotary kiln incinerator

Malaysia is in dire need of alternatives to landfilling for solid waste management. Recently, landfills have faced the problems of overfilling, overflowing of leachates leading to pollution of water resources, and uncontrolled dust emissions adversely affecting the local environment. With the rising cost of urbanization coupled with the high rate of waste generation, one possible method of waste treatment that is receiving particular attention by the government is incineration. Incineration of solid waste is rather new in Malaysia, with limited usage in handling small sources of waste generation such as the municipal solid waste (MSW) of resort islands; however, its potential in ameliorating the problems associated with solid waste treatment may make it an attractive alternative to landfill. This article presents the results of test runs conducted to investigate the performance of a locally designed and manufactured rotary kiln incinerator (RKI). The test runs were conducted using MSW collected from the Shah Alam municipality. The combustion efficiency was analyzed by looking at the temperature profiles and chemical species concentrations. To complement the combustion characteristics measurements, predictions of the air flow in the incinerator during the process were also investigated. The overall performance of the RKI suggests that it is suitable for treating MSW.     

Optimal evaluation of infectious medical waste disposal companies using the fuzzy analytic hierarchy process

Ever since Taiwan’s National Health Insurance implemented the diagnosis-related groups payment system in January 2010, hospital income has declined. Therefore, to meet their medical waste disposal needs, hospitals seek suppliers that provide high-quality services at a low cost. The enactment of the Waste Disposal Act in 1974 had facilitated some improvement in the management of waste disposal. However, since the implementation of the National Health Insurance program, the amount of medical waste from disposable medical products has been increasing. Further, of all the hazardous waste types, the amount of infectious medical waste has increased at the fastest rate. This is because of the increase in the number of items considered as infectious waste by the Environmental Protection Administration. The present study used two important findings from previous studies to determine the critical evaluation criteria for selecting infectious medical waste disposal firms. It employed the fuzzy analytic hierarchy process to set the objective weights of the evaluation criteria and select the optimal infectious medical waste disposal firm through calculation and sorting. The aim was to propose a method of evaluation with which medical and health care institutions could objectively and systematically choose appropriate infectious medical waste disposal firms.     

Perspectives for pilot scale study of RDF in Istanbul,Turkey

Municipal solid waste (MSW) is one of the most important environmental problems arising from rapid urbanization and industrialization. The use of alternative fuels in rotary kilns of cement plants is very important for reducing cost, saving fossil fuels and also eliminating waste materials, accumulated during production or after using these materials. Cement industries has an important potential for supplying preferable solutions to the waste management. Energy recovery from waste is also important for the reduction of CO₂ emissions.This paper presents an investigation of the development of refuse derived fuel (RDF) materials from non-recycling wastes and the determination of its potential use as an alternative fuel in cement production in Istanbul, Turkey. RDF produced from MSW was analyzed and its effects on cement production process were examined. For this purpose, the produced RDF was mixed with the main fuel (LPG) in ratios of 0%, 5%, 10%, 15% and 20%. Then chemical and mineralogical analyses of the produced clinker were carried out. It is believed that successful results of this study will be a good example for municipalities and cement industries in order to achieve both economic and environmental benefits.     

Sustainable disposal of municipal solid waste: Post bioreactor landfill polishing

Sustainable disposal of municipal solid waste (MSW) requires assurance that contaminant release will be minimized or prevented within a reasonable time frame before the landfill is abandoned so that the risk of contamination release is not passed to future generations. This could be accomplished through waste acceptance criteria such as those established by the European Union (EU) that prohibit land disposal of untreated organic matter. In the EU, mechanical, biological and/or thermal pretreatment of MSW is therefore necessary prior to landfilling which is complicated and costly. In other parts of the world, treatment within highly engineered landfills is under development, known as bioreactor landfills. However, the completed bioreactor landfill still contains material, largely nonbiodegradable carbon and ammonia that may be released to the environment over the long-term. This paper provides a conceptual analysis of an approach to ensure landfill sustainability by the rapid removal of these remaining materials, leachate treatment and recirculation combined with aeration. The analysis in this paper includes a preliminary experimental evaluation using real mature leachate and waste samples, a modeling effort using a simplified mass balance approach and input parameters from real typical bioreactor cases, and a cost estimate for the suggested treatment method.     

Municipal solid waste characteristics and management in Allahabad, India

Increasing population levels, rapid economic growth and rise in community living standard accelerates the generation rate of municipal solid waste (MSW) in Indian cities. Improper management of MSW causes hazards to inhabitants. The objectives of the study are to determine the quantitative and qualitative characteristics of MSW along with basic information and to create GIS maps for Allahabad city. The samples have been randomly collected from various locations and analyzed to determine the characteristics of MSW. A questionnaire survey has been carried out to collect data from inhabitants including MSW quantity, collection frequency, satisfaction level, etc. The Geographic Information System (GIS) has been used to analyze existing maps and data, to digitize the existing sanitary ward boundaries and to enter the data about the wards and disposal sites. The total quantity of MSW has been reported as 500 ton/day, and the average generation rate of MSW has been estimated at 0.39 kg/capita/day. The generated ArcGis maps give efficient information concerning static and dynamic parameters of the municipal solid waste management (MSWM) problem such as the generation rate of MSW in different wards, collection point locations, MSW transport means and their routes, and the number of disposal sites and their attributes.     

Trends and problems of solid waste management in developing countries: a case study in seven Palestinian districts

There is a great interest in solving problems related to municipal solid waste (MSW) management in the Palestinian territory. However, few studies have been done to assess the extent of these problems and suggest the best alternative solutions. This study aims at assessing MSW conditions in the seven major districts in northern West Bank, Palestinian territory. The study focuses on comparing several MSW management elements (such as collection, budget, and disposal) in municipalities, village councils, and refugee camps in the studied districts and the problems faced by these institutions in handling the waste. It also provides information on MSW collection service availability and waste disposal practices in the districts studied. It was found that, although MSW collection service was available for 98% of the residents in the areas surveyed, no proper treatment or landfill procedure was followed for the collected waste in most of these areas. Instead, waste burning in open dumpsites was the most common practice. Moreover, due to inefficient collection of waste disposal fees from the residents, municipalities were forced to sometimes cut the collection service and reduce its labor force, especially in villages. The budget for MSW management was between 2% and 8% of the total budget of the municipalities studied, indicating a low priority for this issue.     

Combining AHP with GIS for landfill site selection: A case study in the Lake Beyşehir catchment area (Konya,Turkey)

Landfills are the most common method for the disposal of municipal solid waste (MSW) in Turkey. However, determining the location of landfill sites is a difficult and complex process because it must combine social, environmental and technical parameters. Additionally, it depends on several criteria and regulations. The main objective of this study was to select of a landfill site for the Lake Bey?ehir catchment area. The Bey?ehir Lake is the largest freshwater lake and drinking water reservoir in Turkey, but there is no controlled landfill site in the region. Therefore, the landfill site should be determined such that the lake is protected. To determine the most suitable landfill site, an analytical hierarchy process (AHP) was combined with a geographic information system (GIS) to examine several criteria, such as geology/hydrogeology, land use, slope, height, aspect and distance from settlements, surface waters, roads, and protected areas (ecologic, scientific or historic). Each criterion was evaluated with the aid of AHP and mapped by GIS. Data were assorted into four suitability classes within the study area, i.e., high, moderate, low and very low suitability areas, which represented 3.24%, 7.55%, 12.70% and 2.81%, of the study area, respectively. Additionally, 73.70% was determined to be completely unsuitable for a landfill site. As a result, two candidate landfill sites are suggested and discussed. The final decision for landfill site selection will require more detailed field studies.     

The effect of moisture regimes on the anaerobic degradation of municipal solid waste from Metepec (México)

The State of México, situated in central México, has a population of about 14 million, distributed in approximately 125 counties. Solid waste management represents a serious and ongoing pressure to local authorities. The final disposal site ("El Socavón") does not comply with minimum environmental requirements as no liners or leachate management infrastructure are available. Consequently, leachate composition or the effects of rain water input on municipal solid waste degradation are largely unknown. The aim of this work was to monitor the anaerobic degradation of municipal solid waste (MSW), simulating the water addition due to rainfall, under two different moisture content regimes (70% and 80% humidity). The study was carried out using bioreactors in both laboratory and pilot scales. The variation of organic matter and pH was followed in the solid matrix of the MSW. The leachate produced was used to estimate the field capacity of the MSW and to determine the pH, COD, BOD and heavy metals. Some leachate parameters were found to be within permitted limits, but further research is needed in order to analyze the leachate from lower layers of the disposal site ("El Socavón").     

Pyrolysis technologies for municipal solid waste: A review

Pyrolysis has been examined as an attractive alternative to incineration for municipal solid waste (MSW) disposal that allows energy and resource recovery; however, it has seldom been applied independently with the output of pyrolysis products as end products. This review addresses the state-of-the-art of MSW pyrolysis in regards to its technologies and reactors, products and environmental impacts. In this review, first, the influence of important operating parameters such as final temperature, heating rate (HR) and residence time in the reaction zone on the pyrolysis behaviours and products is reviewed; then the pyrolysis technologies and reactors adopted in literatures and scale-up plants are evaluated. Third, the yields and main properties of the pyrolytic products from individual MSW components, refuse-derived fuel (RDF) made from MSW, and MSW are summarised. In the fourth section, in addition to emissions from pyrolysis processes, such as HCl, SO₂ and NH₃, contaminants in the products, including PCDD/F and heavy metals, are also reviewed, and available measures for improving the environmental impacts of pyrolysis are surveyed. It can be concluded that the single pyrolysis process is an effective waste-to-energy convertor but is not a guaranteed clean solution for MSW disposal. Based on this information, the prospects of applying pyrolysis technologies to dealing with MSW are evaluated and suggested.     

Multi-criteria GIS-based siting of an incineration plant for municipal solid waste

Siting a municipal solid waste (MSW) incineration plant requires a comprehensive evaluation to identify the best available location(s) that can simultaneously meet the requirements of regulations and minimise economic, environmental, health, and social costs. A spatial multi-criteria evaluation methodology is presented to assess land suitability for a plant siting and applied to Santiago Island of Cape Verde. It combines the analytical hierarchy process (AHP) to estimate the selected evaluation criteria weights with Geographic Information Systems (GIS) for spatial data analysis that avoids the subjectivity of the judgements of decision makers in establishing the influences between some criteria or clusters of criteria. An innovative feature of the method lies in incorporating the environmental impact assessment of the plant operation as a criterion in the decision-making process itself rather than as an a posteriori assessment. Moreover, a two-scale approach is considered. At a global scale an initial screening identifies inter-municipal zones satisfying the decisive requirements (socio-economic, technical and environmental issues, with weights respectively, of 48%, 41% and 11%). A detailed suitability ranking inside the previously identified zones is then performed at a local scale in two phases and includes environmental assessment of the plant operation. Those zones are ranked by combining the non-environmental feasibility of Phase 1 (with a weight of 75%) with the environmental assessment of the plant operation impact of Phase 2 (with a weight of 25%). The reliability and robustness of the presented methodology as a decision supporting tool is assessed through a sensitivity analysis. The results proved the system effectiveness in the ranking process.     

Life cycle impact assessment of various waste conversion technologies

Advanced thermal treatment technologies utilizing pyrolysis or gasification, as well as a combined approach, are introduced as sustainable methods to treat wastes in Singapore. Eight different technologies are evaluated: pyrolysis–gasification of MSW; pyrolysis of MSW; thermal cracking gasification of granulated MSW; combined pyrolysis, gasification and oxidation of MSW; steam gasification of wood; circulating fluidized bed (CFB) gasification of organic wastes; gasification of RDF; and the gasification of tyres.Life cycle assessment is carried out to determine the environmental impacts of the various waste conversion systems including global warming potential, acidification potential, terrestrial eutrophication and ozone photochemical formation. The normalization and weighting results, calculated according to Singapore national emission inventories, showed that the two highest impacts are from thermal cracking gasification of granulated MSW and the gasification of RDF; and the least are from the steam gasification of wood and the pyrolysis–gasification of MSW.A simplified life cycle cost comparison showed that the two most costs-effective waste conversion systems are the CFB gasification of organic waste and the combined pyrolysis, gasification and oxidation of MSW. The least favorable – highest environmental impact as well as highest costs – are the thermal cracking gasification of granulated MSW and the gasification of tyres.