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.     

Integrating multi-criteria evaluation techniques with geographic information systems for landfill site selection: a case study using ordered weighted average

This paper presents a GIS-based multi-criteria decision analysis approach for evaluating the suitability for landfill site selection in the Polog Region, Macedonia. The multi-criteria decision framework considers environmental and economic factors which are standardized by fuzzy membership functions and combined by integration of analytical hierarchy process (AHP) and ordered weighted average (OWA) techniques. The AHP is used for the elicitation of attribute weights while the OWA operator function is used to generate a wide range of decision alternatives for addressing uncertainty associated with interaction between multiple criteria. The usefulness of the approach is illustrated by different OWA scenarios that report landfill suitability on a scale between 0 and 1. The OWA scenarios are intended to quantify the level of risk taking (i.e., optimistic, pessimistic, and neutral) and to facilitate a better understanding of patterns that emerge from decision alternatives involved in the decision making process.     

Integrating multi-criteria decision analysis for a GIS-based hazardous waste landfill sitting in Kurdistan Province, western Iran

The evaluation of a hazardous waste disposal site is a complicated process because it requires data from diverse social and environmental fields. These data often involve processing of a significant amount of spatial information which can be used by GIS as an important tool for land use suitability analysis. This paper presents a multi-criteria decision analysis alongside with a geospatial analysis for the selection of hazardous waste landfill sites in Kurdistan Province, western Iran. The study employs a two-stage analysis to provide a spatial decision support system for hazardous waste management in a typically under developed region. The purpose of GIS was to perform an initial screening process to eliminate unsuitable land followed by utilization of a multi-criteria decision analysis (MCDA) to identify the most suitable sites using the information provided by the regional experts with reference to new chosen criteria. Using 21 exclusionary criteria, as input layers, masked maps were prepared. Creating various intermediate or analysis map layers a final overlay map was obtained representing areas for hazardous waste landfill sites. In order to evaluate different landfill sites produced by the overlaying a landfill suitability index system was developed representing cumulative effects of relative importance (weights) and suitability values of 14 non-exclusionary criteria including several criteria resulting from field observation. Using this suitability index 15 different sites were visited and based on the numerical evaluation provided by MCDA most suitable sites were determined.     

Solid waste facilities location using of analytical network process and data envelopment analysis approaches

Selection of the appropriate site for solid waste facilities is a complex problem and requires an extensive evaluation process, because it is very difficult to develop a selection criterion that can precisely describe the preference of one location over another. Therefore selection of these sites can be viewed as a multiple criteria decision-making or multiple attributes decision-making problem. For this purpose, we propose a technique that can effectively take managerial preferences and subjective data into consideration, along with quantitative factors. The tool proposed here relies on the use of the analytical network process (ANP) and to help integrate managerial evaluations into a more quantitatively based decision tool, data envelopment analysis (DEA) is applied. In this paper, a location selection procedure is presented to construct an undesirable facility applying ANP and DEA approaches in two stages. In the first stage ANP approach is used, results of this stage are inputs for the second stage. In this stage, DEA is applied to select the best location. Finally, to illustrate the proposed framework, at "Results and discussion" section, a total of four undesirable facility locations are evaluated.     

Siting MSW landfills with a spatial multiple criteria analysis methodology

The present work describes a spatial methodology which comprises several methods from different scientific fields such as multiple criteria analysis, geographic information systems, spatial analysis and spatial statistics. The final goal of the methodology is to evaluate the suitability of the study region in order to optimally site a landfill. The initial step is the formation of the multiple criteria problem's hierarchical structure. Then the methodology utilizes spatial analysis processes to create the evaluation criteria, which are mainly based on Greek and EU legislation, but are also based on international practice and practical guidelines. The relative importance weights of the evaluation criteria are estimated using the analytic hierarchy process. With the aid of the simple additive weighting method, the suitability for landfill siting of the study region is finally evaluated. The resulting land suitability is reported on a grading scale of 0-10, which is, respectively, from least to most suitable areas. The last step is a spatial clustering process, which is being performed in order to reveal the most suitable areas, allowing an initial ranking and selection of candidate landfill sites. The application of the presented methodology in the island of Lemnos in the North Aegean Sea (Greece) indicated that 9.3% of the study region is suitable for landfill siting with grading values greater than 9.     

Fundamental processes and implications during in situ aeration of old landfills

Results of investigations from many old landfills in Germany and Europe indicate that significant emissions occur under conventional landfill operating conditions (i.e., anaerobic conditions). Significant emissions via the gas phase are predicted to last at least three decades after landfill closure, while leachate emissions are predicted to continue for many decades, potentially even lasting for centuries. When considering the specific type and quality, and quite often lack of, protection barriers associated with old landfills, these leachate and gas emissions may result in a significant negative impact on the environment. However, complete sealing of the landfill only temporarily reduces emissions because dry-conservation of the biodegradable waste fraction results, thus not allowing any severe reduction in the emission and hazardous potential of the landfill to occur. If noticeable damage of the surface capping system occurred in these landfills, infiltrating water would restart the interrupted emission formation. In contrast, aerobic in situ stabilization by means of low pressure aeration attempts to stabilize and modify the inventory of organic matter inside the landfill, acting to reduce the emission potential in a more sustainable manner. By enabling faster and more extensive aerobic degradation processes in the landfill (compared with anaerobic processes), the organics (e.g., hydrocarbons) are degraded significantly faster, resulting in an increased carbon discharge via the gas phase, as well as reduced leachate concentrations. Because carbon dioxide (CO(2)) is the main compound in the extracted off-gas (instead of methane (CH(4)), which dominated under anaerobic landfill conditions), the negative impact of diffuse LFG emissions towards an increased global warming effect may be significantly lowered. With respect to leachate quality, a reduction of organic compounds as well as ammonia-nitrogen can be expected. In addition to these positive ecological effects, aerobic in situ stabilization is associated with significant cost savings potential due to both quantitative and qualitative reductions in the aftercare period. This paper describes the fundamental processes and implications of in situ landfill aeration. Additionally, possible criteria for defining an endpoint of the active aeration process are presented and discussed.     

Environmental diagnosis methodology for municipal waste landfills

A large number of countries are involved in a process of transformation with regard to the management of municipal solid waste. This process is a consequence of environmental requirements that occasionally materialise in legislation, such as the European Council Directive 31/99/EC on waste release in the European Union. In some cases, the remediation of old landfills can be carried out in compliance with environmental requirements; in other cases, it is necessary to proceed with the closure of the landfill and to assimilate it into its own environment. In both cases, it is necessary to undertake a diagnosis and characterisation of the impacted areas in order to develop an adequate action plan. This study presents a new methodology by which environmental diagnosis of landfill sites may be carried out. The methodology involves the formulation of a series of environmental indeces which provide information concerning the potential environmental problems of the landfills and the particular impact on different environmental elements, as well as information related to location, design and operation. On the basis of these results, it would be possible to draw up action plans for the remediation or closure of the landfill site. By applying the methodology to several landfills in a specific area, it would be possible to prioritize the order of actions required.     

Findings from long-term monitoring studies at MSW landfill facilities with leachate recirculation

This paper presents findings from long-term monitoring studies performed at full-scale municipal solid waste landfill facilities with leachate recirculation. Data from two facilities at a landfill site in Delaware, USA were evaluated as part of this study: (1) Area A/B landfill cells; and (2) two test cells (one with leachate recirculation and one control cell). Data from Area A/B were compared with proposed waste stability criteria for leachate quality, landfill gas production, and landfill settlement. Data from the test cells were directly compared with each other. Overall, the trends at Area A/B pointed to the positive effects (i.e., more rapid waste degradation) that may be realized through increasing moisture availability in a landfill relative to the reported behavior of more traditionally operated (i.e., drier) landfills. Some significant behavioral differences between the two test cells were evident, including dissimilarities in total landfill gas production quantity and the extent of waste degradation observed in recovered time capsules. Differences in leachate quality were not as dramatic as anticipated, probably because the efficiency of the leachate recirculation system at distributing leachate throughout the waste body in the recirculation cell was low.     

The potential for aeration of MSW landfills to accelerate completion

Landfilling is a popular waste disposal method, but, as it is practised currently, it is fundamentally unsustainable. The low short-term financial costs belie the potential long-term environmental costs, and traditional landfill sites require long-term management in order to mitigate any possible environmental damage. Old landfill sites might require aftercare for decades or even centuries, and in some cases remediation may be necessary. Biological stabilisation of a landfill is the key issue; completion criteria provide a yardstick by which the success of any new technology may be measured. In order for a site to achieve completion it must pose no risk to human health or the environment, meaning that attenuation of any emissions from the site must occur within the local environment without causing harm. Remediation of old landfill sites by aerating the waste has been undertaken in Germany, the United States, Italy and The Netherlands, with considerable success. At a pilot scale, aeration has also been used in newly emplaced waste to accelerate stabilisation. This paper reviews the use of aerobic landfill worldwide, and assesses the ways in which the use of aerobic landfill techniques can decrease the risks associated with current landfill practices, making landfill a more sustainable waste disposal option. It focuses on assessing ways to utilise aeration to enhance stabilisation. The results demonstrated that aeration of old landfill sites may be an efficient and cost-effective method of remediation and allow the date of completion to be brought forward by decades. Similarly, aeration of newly emplaced waste can be effective in enhancing degradation, assisting with completion and reducing environmental risks. However, further research is required to establish what procedure for adding air to a landfill would be most suitable for the UK and to investigate new risks that may arise, such as the possible emission of non-methane organic compounds.     

Environmental assessment of solid waste landfilling technologies by means of LCA-modeling

By using life cycle assessment (LCA) modeling, this paper compares the environmental performance of six landfilling technologies (open dump, conventional landfill with flares, conventional landfill with energy recovery, standard bioreactor landfill, flushing bioreactor landfill and semi-aerobic landfill) and assesses the influence of the active operations practiced on these performances. The environmental assessments have been performed by means of the LCA-based tool EASEWASTE, whereby the functional unit utilized for the LCA is "landfilling of 1ton of wet household waste in a 10m deep landfill for 100 years". The assessment criteria include standard categories (global warming, nutrient enrichment, ozone depletion, photo-chemical ozone formation and acidification), toxicity-related categories (human toxicity and ecotoxicity) and impact on spoiled groundwater resources. Results demonstrate that it is crucially important to ensure the highest collection efficiency of landfill gas and leachate since a poor capture compromises the overall environmental performance. Once gas and leachate are collected and treated, the potential impacts in the standard environmental categories and on spoiled groundwater resources significantly decrease, although at the same time specific emissions from gas treatment lead to increased impact potentials in the toxicity-related categories. Gas utilization for energy recovery leads to saved emissions and avoided impact potentials in several environmental categories. Measures should be taken to prevent leachate infiltration to groundwater and it is essential to collect and treat the generated leachate. The bioreactor technologies recirculate the collected leachate to enhance the waste degradation process. This allows the gas collection period to be reduced from 40 to 15 years, although it does not lead to noticeable environmental benefits when considering a 100 years LCA-perspective. In order to more comprehensively understand the influence of the active operations (i.e., leachate recirculation, waste flushing and air injection) on the environmental performance, the time horizon of the assessment has been split into two time periods: years 0-15 and 16-100. Results show that if these operations are combined with gas utilization and leachate treatment, they are able to shorten the time frame that emissions lead to environmental impacts of concern.     

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.     

Landfill modelling in LCA - a contribution based on empirical data

Landfills at various stages of development, depending on their age and location, can be found throughout Europe. The type of facilities goes from uncontrolled dumpsites to highly engineered facilities with leachate and gas management. In addition, some landfills are designed to receive untreated waste, while others can receive incineration residues (MSWI) or residues after mechanical biological treatment (MBT). Dimension, type and duration of the emissions from landfills depend on the quality of the disposed waste, the technical design, and the location of the landfill. Environmental impacts are produced by the leachate (heavy metals, organic loading), emissions into the air (CH(4), hydrocarbons, halogenated hydrocarbons) and from the energy or fuel requirements for the operation of the landfill (SO(2) and NO(x) from the production of electricity from fossil fuels). To include landfilling in an life-cycle assessment (LCA) approach entails several methodological questions (multi-input process, site-specific influence, time dependency). Additionally, no experiences are available with regard to mid-term behaviour (decades) for the relatively new types of landfill (MBT landfill, landfill for residues from MSWI). The present paper focuses on two main issues concerning modelling of landfills in LCA: Firstly, it is an acknowledged fact that emissions from landfills may prevail for a very long time, often thousands of years or longer. The choice of time frame in the LCA of landfilling may therefore clearly affect the results. Secondly, the reliability of results obtained through a life-cycle assessment depends on the availability and quality of Life Cycle Inventory (LCI) data. Therefore the choice of the general approach, using multi-input inventory tool versus empirical results, may also influence the results. In this paper the different approaches concerning time horizon and LCI will be introduced and discussed. In the application of empirical results, the presence of data gaps may limit the inclusion of several impact categories and therefore affect the results obtained by the study. For this reason, every effort has been made to provide high-quality empirical LCI data for landfills in Central Europe.     

Assessment of two thermally treated drill mud wastes for landfill containment applications.

Offshore oil and gas drilling operations generate significant amounts of drill mud waste, some of which is transported onshore for subsequent thermal treatment (i.e. via thermal remediation). This treatment process results in a mineral waste by-product (referred to as thermally treated drill mud waste; TTDMW). Bentonites are originally present in many of the drill mud products and it is hypothesized that TTDMW can be utilized in landfill containment applications (i.e. cover or base liner). The objective of this paper is to examine the feasibility of this application by performing various physical and chemical tests on two TTDMW samples. It is shown that the two TTDMW samples contained relatively small amounts of clay-sized minerals although hydraulic conductivity values are found to be less than 10(-8) m/s. Organic carbon contents of the samples were approximately 2%. Mineralogy characterization of the samples confirmed varying amounts of smectite, however, peak friction angles for a TTDMW sample was greater than 36 degrees. Chemical characterization of the TTDMW samples show potential leaching of barium and small amounts of other heavy metals. Discussion is provided in the paper on suggestions to assist in overcoming regulatory issues associated with utilization of TTDMW in landfill containment applications.     

A decision support system for assessing landfill performance

Designing environmentally sound landfills is a challenging engineering task due to complex interactions of numerous design variables; such as landfill size, waste characteristics, and site hydrogeology. Decision support systems (DSS) can be utilized to handle these complex interactions and to aid in a performance-based landfill design by coupling system simulation models (SSM). The aim of this paper is to present a decision support system developed for a performance-based landfill design. The developed DSS is called Landfill Design Decision Support System – LFDSS. A two-step DSS framework, composed of preliminary design and detailed design phases, is set to effectively couple and run the SSMs and calculation modules. In preliminary design phase, preliminary design alternatives are proposed using general site data. In detailed design phase, proposed design alternatives are further simulated under site-specific data using SSMs for performance evaluation. LFDSS calculates the required landfill volume, performs landfill base contour design, proposes preliminary design alternatives based on general site conditions, evaluates the performance of the proposed designs, calculates the factor of safety values for slope stability analyses, and performs major cost calculations. The DSS evaluates the results of all landfill design alternatives, and determines whether the design satisfies the predefined performance criteria. The DSS ultimately enables comparisons among different landfill designs based on their performances (i.e. leachate head stability, and groundwater contamination), constructional stability and costs. The developed DSS was applied to a real site, and the results demonstrated the strengths of the developed system on designing environmentally sound and feasible landfills.     

An integrated multi criteria approach for landfill siting in a conflicting environmental, economical and socio-cultural area

Landfill site selection is a complicated multi criteria land use planning that should convince all related stakeholders with different insights. This paper addresses an integrating approach for landfill siting based on conflicting opinions among environmental, economical and socio-cultural expertise. In order to gain optimized siting decision, the issue was investigated in different viewpoints. At first step based on opinion sampling and questionnaire results of 35 experts familiar with local situations, the national environmental legislations and international practices, 13 constraints and 15 factors were built in hierarchical structure. Factors divided into three environmental, economical and socio-cultural groups. In the next step, the GIS-database was developed based on the designated criteria. In the third stage, the criteria standardization and criteria weighting were accomplished. The relative importance weights of criteria and subcriteria were estimated, respectively, using analytical hierarchy process and rank ordering methods based on different experts opinions. Thereafter, by using simple additive weighting method, the suitability maps for landfill siting in Marvdasht, Iran, was evaluated in environmental, economical and socio-cultural visions. The importance of each group of criteria in its own vision was assigned to be higher than two other groups. In the fourth stage, the final suitability map was obtained after crossing three resulted maps in different visions and reported in five suitability classes for landfill construction. This map indicated that almost 1224 ha of the study area can be considered as best suitable class for landfill siting considering all visions. In the last stage, a comprehensive field visit was performed to verify the selected site obtained from the proposed model. This field inspection has confirmed the proposed integrating approach for the landfill siting.     

Influence of the geomembrane on time-lapse ERT measurements for leachate injection monitoring

Leachate recirculation is a key process in the operation of municipal waste landfills as bioreactors. To quantify the water content and to evaluate the leachate injection system, in situ methods are required to obtain spatially distributed information, usually electrical resistivity tomography (ERT). However, this method can present false variations in the observations due to several parameters. This study investigates the impact of the geomembrane on ERT measurements. Indeed, the geomembrane tends to be ignored in the inversion process in most previously conducted studies. The presence of the geomembrane can change the boundary conditions of the inversion models, which have classically infinite boundary conditions. Using a numerical modelling approach, the authors demonstrate that a minimum distance is required between the electrode line and the geomembrane to satisfy the good conditions of use of the classical inversion tools. This distance is a function of the electrode line length (i.e. of the unit electrode spacing) used, the array type and the orientation of the electrode line. Moreover, this study shows that if this criterion on the minimum distance is not satisfied, it is possible to significantly improve the inversion process by introducing the complex geometry and the geomembrane location into the inversion tools. These results are finally validated on a field data set gathered on a small municipal solid waste landfill cell where this minimum distance criterion cannot be satisfied.     

Analysis of land suitability for the siting of inter-municipal landfills in the Cuitzeo Lake Basin, Mexico

This paper presents three spatial decision-support models (Boolean logic, binary evidence and overlapping index of multiple class maps) to perform a land suitability analysis for sanitary landfill siting. The study was carried out in the basin of Lake Cuitzeo, Mexico, with the objective of locating areas that comply with environmental regulations and with the inter-municipality criterion, i.e., that are accessible by at least two municipalities. Biophysical and socio-economic data were processed in a Geographic Information System (GIS). The three models differ in their complexity and restrictiveness. The Boolean logic model is easier to apply and more restrictive than the other two, because it is based on the assessment of single attributes. On the other hand, the binary data and overlapping index methods are relatively more complex because they require attribute weighting. The results showed that 23 of the 28 municipalities included in the basin have at least one area that was classified as highly suitable. The most suitable areas covered from 63.8 to 204.5 km(2) (from 1.5% to 5%), and they are not distributed homogeneously, but clustered around four main sites. The larger and most suitable of these sites is located in the central part of the basin, and it can be accessed by five of the most densely populated municipalities. The proposed approach represents a low-cost alternative to support a common spatial decision-making process in developing countries.     

Siting MSW landfill using weighted linear combination and analytical hierarchy process (AHP) methodology in GIS environment (case study: Karaj)

Selection of landfill site is a complex process and needs many diverse criteria. The purpose of this paper is to evaluate the suitability of the studied site as landfill for MSW in Karaj. Using weighted linear combination (WLC) method and spatial cluster analysis (SCA), suitable sites for allocation of landfill for a 20-year period were identified. For analyzing spatial auto-correlation of the land suitability map layer (LSML), Maron’s I was used. Finally, using the analytical hierarchy process (AHP), the most preferred alternative for the landfill siting was identified. Main advantages of AHP are: relative ease of handling multiple criteria, easy to understand and effective handling of both qualitative and quantitative data.As a result, 6% of the study area is suitable for landfill siting and third alternative was identified as the most preferred for siting MSW landfill by AHP.The ranking of alternatives were obtained only by applying the WLC approach showed different results from the AHP. The WLC should be used only for the identification of alternatives and the AHP is used for prioritization. We suggest the employed procedure for other similar regions.     

Assessment of the potential health risks associated with the dissemination of micro-organisms from a landfill site

In planning for a new sanitary landfill site, the City of Edmonton, Canada considered the potential for dissemination of micro-organisms via aerosols and by gulls that feed on the refuse. The health impacts on the residents and chicken and mushroom farming activities in the vicinity of the proposed location were assessed. Conclusions based on a review of information in the literature and in the City's planning documents were: (1) the densities of airborne microbes generated at the landfill site would be less than those observed at sewage treatment plants which cause very little health risk; (2) chicken and mushroom farming operations generate very high densities of airborne microbes and the small numbers of microbes that might originate from the landfill site would be insignificant; (3) the proximity of the proposed landfill location to an existing landfill site would not likely change the number of gulls in the area; (4) sound agricultural practices (such as preventing wild birds from contacting poultry, or their water supplies, food and new litter) will minimize risk of the spread of pathogens to chickens from gulls.     

Modelling of environmental impacts of solid waste landfilling within the life-cycle analysis program EASEWASTE

A new computer-based life-cycle assessment model (EASEWASTE) has been developed to evaluate resource and environmental consequences of solid waste management systems. This paper describes the landfilling sub-model used in the life-cycle assessment program EASEWASTE, and examines some of the implications of this sub-model. All quantities and concentrations of leachate and landfill gas can be modified by the user in order to bring them in agreement with the actual landfill that is assessed by the model. All emissions, except the generation of landfill gas, are process specific. The landfill gas generation is calculated on the basis of organic matter in the landfilled waste. A landfill assessment example is provided. For this example, the normalised environmental effects of landfill gas on global warming and photochemical smog are much greater than the environmental effects for landfill leachate or for landfill construction. A sensitivity analysis for this example indicates that the overall environmental impact is sensitive to the gas collection efficiency and the use of the gas, but not to the amount of leachate generated, or the amount of soil or liner material used in construction. The landfill model can be used for evaluating different technologies with different liners, gas and leachate collection efficiencies, and to compare the environmental consequences of landfilling with alternative waste treatment options such as incineration or anaerobic digestion.