Advances In Natural And Applied Sciences

2020 September-December 14(3): pages 89-95 DOI: 10.22587/anas.2020.14.3.12 Research Article AENSI Publications

Regional landfill planning for improvement of waste management in ,

Chelsea Langa1, Kengo Nakamura, Noriaki Watanabe, Takeshi Komai2

1Graduate School of Environmental Studies, Tohoku University, Sendai City, Japan 2Graduate School of Environmental Studies, Tohoku University, Sendai City, Japan

Correspondence Author: Chelsea Langa, Graduate School of Environmental Studies, Tohoku University, Sendai City, Japan E-mail: [email protected]

Received date: 22 August 2020 , Accepted date: 25 September 2020

Copyright: © 2020 Chelsea Langa. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Abstract

This study consisted of selecting potential landfill sites in where population increased from about 1 million to 2 million from 1997 to 2017. This growth resulted in waste increase and space reduction which are conflicting aspects in the selection of landfill sites. Eight criteria representing geophysical and social characteristics were analyzed on the Geographic Information Systems environment, namely soil, geology, slope, land use, road network, river, lakes and special protection units. Suitability indexes of each layer map where individually analyzed and later overlaid on the ArcMap environment. The maps were classified into 3 degrees, unsuitable, moderate and suitable. Analytical Hierarchy Process was used to measure the degree of importance and weights of each criteria.

Finally, results show that 74% of the area is unsuitable, 7 % is moderate and 19 % is suitable. Results indicated that a regional landfill is necessary for the four disctricts to improve their waste management system.

Keywords: Landfill; waste; suitable; GIS; AHP

INTRODUCTION

The waste management system is critical for the treatment and elimination of wastes produced. However, this is a complex system due to increasing quantities of waste produced as a result of population growth and lifestyle changes [1]. The landfill selection is one of the most difficult due to the requirements of space and the consideration of many suitability criteria. It requires the analysis of land use characteristics and feasibility aspects [2]. Moreover, various decision-makers must intervene to ensure the application of technical, environmental and social principles. However, due to the many criteria to analyze, site selection is also considered a multicriteria decision problem [3]. Social acceptance is also important. If there is no social acceptance, the citizens may enter into conflicts with waste planners [2, 4]. Regardless of the challenges in the selection process, landfills are necessary to close the waste management system [2]. Moreover, they are the most cost-effective methods of waste disposal [5]. If properly selected, they prevent negative effects on the environment [6]. Landfills require space. Spatial analysis methods such as Geographic Information Systems (GIS) are effective tools for space planning, either single or in combination with other tools. [2]. GIS has been used in most site selection studies due to advances in the technology, sophisticated layering and overlay procedures [2; 3; 6]. Data representing geophysical and social conditions of the study area is also necessary. This data are the criteria used to evaluate the suitability of a proposed site [4; 5; 7]. It is important to decide the degree of importance of each criterion; however, not all criteria have the same importance. Therefore, combining GIS with the Analytic Hierarchy Process (AHP) is very useful [6; 8]. The AHP is a Advances in Natural and Applied Sciences ISSN-1995-0772 EISSN-1998-1090 Homepage: http://www.aensiweb.com/ANAS/ 90 Citation: Chelsea Langa et al, 2020. Regional landfill planning for improvement of waste management in Maputo, Mozambique Advances in Natural and Applied Sciences., 14(3): 89-95. DOI: 10.22587/anas.2020.14.3.12 measurement tool developed by Saaty, structured in order to break the problem in stages. This tool helps the decision- makers define degrees of importance of the criteria [6; 9]. While this decision as to which criteria is more important to be deliberative, Multi-criteria Decision Methods (MCDM) such as AHP guarantee transparency, structure and formality to the process [8; 9]. The studies that have laid the foundation for the present study are [10], which has used land suitability analysis based solely on groundwater parameters in Turkey. Nas et al., [5] and Sener et al., [7] have applied GIS to identify landfill sites in Turkey as well; however, combined with different MCDA. Josimović and I. Marić [2] focused on the parameters for regional waste landfill planning in Serbia. Eskandari, Homaee and Mahmodi [11] have applied the method for Iran, combining many tools for robustness. Colvero et al., [12] applied new variables such as waste production and population growth prediction to its analysis, not only identify new landfills but to assess existing ones; the study area is located in Brazil.

Background of the study Great Maputo area, located in Maputo province, is a composite of four districts: Maputo, , Boane and Marracuene districts. Altogether they are home to about 3 million inhabitants.

Figure 1: Population growth in Great Maputo area from 1997 to 2017.

The population has doubled from 1997 to 2017 (fig. 1) [13; 14] causing pressure to waste management planners because of growing quantities of waste. More waste is produced and new sites are required for disposal. Meanwhile, two landfills operate in the study area. one located in Maputo district, and the other in Matola district. These landfills are not engineered and lack compliance with sanitary rules and waste management rules [15]. Currently, in Maputo district, 1100 tons of waste are produced per day. About 80% of waste is disposed of Maputo landfill, while the remaining 20% are left in illegal open spaces or remain in the collection bins. As for Matola, Boane and Marracuene districts, there is no accurate data about the waste generation. It is only known that part of their waste is disposed of in Matola’s landfill, while they remain burnt or buried. This lack of data poses limitations for this study [1; 16; 17]. The landfill of Maputo district has reached its full capacity and requires closure. Moreover, illegal dumpsites are increasing inside the cities. Selecting new waste landfills for this area is important but is also difficult because citizens do not accept them due to their effects: bad odours, fires and smokes, rodents, smokes, land depreciation as well as related diseases. Additionally, they can leachate materials through the soil to the groundwater [1; 16; 17; 18; 19]. Therefore, this work aims to select spaces for regional landfills by analyzing land characteristics and selecting spaces that not affect nearby citizens nor compromise environmental standards. This work expects to be a tool for waste management planning that will expand on previous studies about waste management in Mozambique [1, 16; 17]. The new point of the research is the application of land use data to waste management research.

MATERIALS AND METHODS

Study Area 91 Citation: Chelsea Langa et al, 2020. Regional landfill planning for improvement of waste management in Maputo, Mozambique Advances in Natural and Applied Sciences., 14(3): 89-95. DOI: 10.22587/anas.2020.14.3.12

Maputo province is situated in the southern Mozambique between Latitude 25°55's, Longitude 32°34'e, at an Altitude of 39 m, (fig. 2). The surface area is of 26.058 square Km2 [13; 20]. It is divided into four districts and four municipalities. Four districts compose the Great Maputo are – Maputo, Matola, Boane and Marracuene. The population of the province is of 3.000.000 inhabitants, distributed through the 8 districts, however, about 2.000.000 live in the Great Maputo alone [14]. A tropical savanna climate is predominant, with a rainy season from October to March, and a dry season from April to September. The terrain is made of lowlands around 200 m above sea level, sometimes reaching 100 m [20]. The geology of the area consists of quaternary sediments and volcanic rocks in the south [21]. The structure consists of littoral accumulation zone corresponding to beach and tidal deposits; a coastal zone inclined to the sea. Moreover, interior dunes and sand units, coastal dunes and alluvium characterize the area [21]. The area is covered by bushes, grasslands in the interior and wetlands near the sea. Finally, the considerable land uses are agriculture, mainly the mixed crop production, settlement and built area [20].

Data and Elaboration of Selection Process For the preparation of data, the soil characteristics, access ways, surface water and land uses were considered, represented by eight criteria layer maps. These attributes were selected based on their relevance for the soil and water protection. Moreover, for an optimal selection, human land should suffer the least alterations possible. Criteria were based on literature review as well as regulation, namely: land use and cover; road network; river; lake; geology; soil; protection units and slope [2; 4; 5; 6; 7]. The data were obtained at the National Institute of Remote Sensing of Mozambique, uploaded from the Landsat TM 30 m. The databases associated with each criterion were organized, compared with supporting literature and information regarding the study area. This process is crucial for evaluating the accuracy of the attributes in the input layer maps. Because each layer map has its own type of data and unity, they would not be able to be compared with one another nor equally measured. Hence, they were converted to raster files and reclassified into a single scale of evaluation.

Reclassification and Suitability Degrees The reclassification process consisted of creating three distinct classes, ranging from 0 to 2, assigned linearly. Attributes that were following landfill construction received the value of 2, attributes with moderate degrees received the value of 1 and attributes incapable of landfills construction received the degree of 0, forming three classes of suitability. Perfectly unsuitable attributes were masked and removed from posterior analysis such as water bodies, major roads, urban areas, special unit protection areas. Additionally buffer zones were further assigned to these restricted areas to ensure minimum 500 meters’ distance. Carbonates rocks, agricultural activities, industrial areas, wetlands, mangroves, sand dunes and slopes higher than 8% were also considered unsuitable [2; 5; 10; 15; 18].

Figure 2: The study area. Great Maputo area 92 Citation: Chelsea Langa et al, 2020. Regional landfill planning for improvement of waste management in Maputo, Mozambique Advances in Natural and Applied Sciences., 14(3): 89-95. DOI: 10.22587/anas.2020.14.3.12

Attributes with a moderate degree were clayey alluvium soils, terrains and undifferentiated deposits, areas located between 500 and 1500 meters away from water bodies and main roads, areas located between 500 and 3500 m away from protection units [22; 23]. Preferred attributes were those with slope between 3% and 8%, bushes, grasslands, clayey soils, basic rocks, acidic and intermediate rocks, areas located more than 1500 m far from water bodies, areas located more than 3500 far from protection areas [2; 5; 10; 15]. All these steps were grouped into the preliminary screening process, applied in previous researches [6].

Pairwise comparisons of criteria based on the analytical hierarchy process Pairwise comparisons require that the decision-maker defines the problem and the type of knowledge necessary, moreover, alternatives must be organized into a hierarchy [9]. Therefore, to select the best areas, a clear set of negative effects caused by landfills was analyzed. Based on their high potential of landfills to damage soil and groundwater through leachates [9; 18] the alternatives were defined: soil protection, water protection as well as land uses preservation. Pairwise comparisons were made (table 1) and the consistency index (CI) calculated in order to evaluate the reliability of the previous calculations, based on the formula below

CI = , Finally, the consistency ratio (CR) was calculated and its result was lower than 0.1 as recommended (table 1) [9]. Based on the alternatives previously set, land use, surface water, soil and geology had higher weights (table 1).

Weighted overlay and final analysis After the calculation of weights, all layer maps were overlaid, and a final suitability map was obtained (fig. 3). To perform the weighted overlay analysis, all input layer maps must make a sum total of 100%, which is the total of each input layer map weight of influence. The next step was to choose the best districts to have a potential regional landfill among the suitable areas identified. An area for landfill should have low value for other uses, however, it should be able to prevent contamination of soils and groundwater. Which means that, in addition to the suitability criteria, it is necessary to apply engineering tools to prevent leachate and other negative effects. It must also not cause adverse effects to neighbourhood citizens [7; 15]. Many researchers have selected either one or more sites, while others have opted for optimal areas instead of a precise site [24]. The latter approach was used in this study. The choice a single precise area requires that on-site studies take place to evaluate existing ecology or biodiversity, technical aspects of constructions, existing households and further required analysis [24]. Because these steps were not possible within the scope of this study, selecting a single point was deemed unnecessary. The final selection was made by weighted overlay analysis in which the weights calculated by AHP were used in overlay tool of ArcMap.

RESULTS AND DISCUSSION

In this study, the characteristics of the study area, represented by eight criteria, were analyzed. Construction requirements and regulation were also analyzed to make the criteria conform to environmental and safety standards [2; 5; 7]. Besides, the understanding of the importance of a landfill greatly contributed to the weight each criterion received from the pairwise comparison [9]. AHP is concerned with firstly defining the hierarchy of the alternatives. In this study, the alternatives were the protection of soil, protection of water resources and the preservation of land use.

Land use criteria Landfills may be properly selected based on geophysical criteria, and however, if citizens do not accept them, some indifference to waste issues or even conflicts may arise between them and waste planners, leading to a poor waste management process [25]. This is the result of low awareness from citizens combined with a poor participating system 93 Citation: Chelsea Langa et al, 2020. Regional landfill planning for improvement of waste management in Maputo, Mozambique Advances in Natural and Applied Sciences., 14(3): 89-95. DOI: 10.22587/anas.2020.14.3.12 from waste planners. From that place, this criterion received high importance for the study. Most areas of Boane, Matola and Marracuene districts practice agriculture activities on different levels [13; 14] reason why soil was considered an instrument of work and a priority to secure. The loss of soil quality for agriculture, motivated by pollution from waste materials may result in damages in agriculture activities. All agricultural uses and urban areas were considered unsuitable for protecting not only the soils but also the citizen’s health and safety.

Water resources Rivers and groundwaters are the sources of drinking water and irrigation for agriculture. More than 60% of the citizens in the Great Maputo are supplied by groundwater, especially in areas where the pipe system cannot reach, such as parts of Boane and [18].

Table 1: Pairwise comparison matrix with weights of criteria. LUC - Land use, SOI – Soil, GEO – Geology, SLP – Slope, PU – Protection units, RIV – River, LK – Lake, RN – Road network. λmax = 8.5024; Consistency index (CI) = 0.0717; Consistency ratio (CR) = 0.0509 ˂0.1. Criteria LUC SOI GEO SLP PU RIV LK RN Weight

LUC 1 3 3 7 5 3 3 5 31

SOI 1/3 1 1 5 4 1 1 4 14 GEO 1/3 1/1 1 6 4 1 1 4 14 SLP 1/7 1/5 1/6 1 1/5 1/5 1/5 2 3 PU 1/5 1/4 1/4 5 1 1/3 1/3 4 7 RIV 1/3 1/1 1/1 5 3 1 1 5 14

LK 1/3 1/1 1/1 5 3 1/1 1 5 14 RN 1/5 1/4 1/4 1/2 1/4 1/5 1/5 1 3

The remaining population is supplied by river water from the Umbeluzi river [20]. Groundwater quality studies along with soil and geology data indicate that Maputo area is made of plains of unconsolidated deposits of sand units. In Boane district there is occurrence of acidic rocks located in the interior [20]. Below the predominant sandy soils lie a highly rechargeable, unconfined aquifer [10; 18; 21]. The best setting for landfills are massive lithological units and clays in continuous layers [10]. Therefore, layers of basic, acidic and intermediate rocks were preferred over other types, such as carbonates, that were considered unsuitable. Sandy soils are not propitius for landfill because of the high potential of leachate therefore were considered moderate [10]. Regarding to slopes, if too steep they can cause potential runoff from landfills that can contaminate neighbor areas, however, almost all area has a slope lower than 8% which is not too steep, hence favorable [2].

Suitability Areas All three suitability degrees were identified in the final map (fig. 3) - unsuitable, moderate and suitable. About 74% of the study area is unsuitable for landfills, following, 7 % of the area is moderate and only 19 % is suitable. Suitable areas (fig. 3), in green color are located in the southern, central and western of Boane disctrict while other suitable areas are located in the west of Matola district and Marracuene district. Suitable areas are consistent with acidic and intermediate rocks, basic rocks and land use such as grassland and bushes, therefore safeguarding human uses such as housing and agriculture. Contrary, problematic areas, represented by colour gray, are consistent with extensive agriculture uses and urban areas. The moderate areas were represented by yellow colour and are consistent with barren lands and undifferentiated deposits. Analyzed by districts, Matola had a higher percentage of suitable areas - 42%, Boane district followed with 24%, Marracuene district had only 15% and Maputo city had the lowest suitability with only 6%. As for problematic areas Maputo district had 88%, followed by Marracuene with 79%, Boane district had 94 Citation: Chelsea Langa et al, 2020. Regional landfill planning for improvement of waste management in Maputo, Mozambique Advances in Natural and Applied Sciences., 14(3): 89-95. DOI: 10.22587/anas.2020.14.3.12

66% of problematic areas and the last was Matola district with 58%. Since Matola district had a higher percentage of suitable areas and is located in the central area, it is recommended for a regional landfill. Due to its location, it can be accessed by the other three districts by waste trucks. Therefore this study recommends that Matola district be considered for a regional landfill.

CONCLUSION

In this study, eight criteria were analyzed, representing the geophysical and social characteristics of the study area. The criteria were slope, soil type, land use, geology, distance to protection units, distance to roads, distance to rivers and lakes. These criteria where analyzed reclassified and overlaid leading to the selection of unsuitable, moderate and suitable areas.

Figure 3. Final suitability map showing degrees of suitability and their respective distribution.

All districts presented suitable areas for landfills. If an integrated plan is developed following the waste management goals of the province as a whole, Matola district should be recommended for a regional landfill. Although each of these districts has separate planning, regional planning would be a key point in overcoming the shortage of funding to manage landfills in Maputo province. Maputo district, the most urbanized area, should consider the rapid yet effective solutions to enhance waste management system efficiencies, such as separation on the source and small scale recycling. Meanwhile, the other municipalities would benefit from the installation of composting facilities.

Acknowledgement The authors sincerely thank Junko Hara (National Institute of Advanced Industrial Science and Technology of Japan) for her assistance with the technical analysis.

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