Assessment of municipal solid waste disposal suitability using multi-criteria analysis in Bogotá

Where should a city of 8 million people put its garbage when the only operating landfill is expected to reach capacity within six years? This research applied a GIS-based multi-criteria analysis (MCA) to identify suitable sites for municipal solid-waste disposal in the metropolitan area of Bogotá, Colombia. Eight suitability criteria—slope, geology, distance from surface water, land use, road accessibility, population density, soil type, and flood risk—were evaluated and weighted using the analytical hierarchy process (AHP) with input from 14 environmental-planning professionals. Weighted overlay in ArcGIS Pro generated a composite suitability map classifying the study area into five zones: optimal (4.2% of area), suitable (11.8%), moderate (23.7%), marginal (31.4%), and excluded (28.9%). The optimal zone is concentrated in the southwestern plateau, where gentle slopes (< 8%), clay-rich soils, and distance from major waterways coincide with low population density and existing road access. A sensitivity analysis showed that the ranking was most responsive to changes in the distance-from-water and geology criteria weights, and least sensitive to road-access weight. Two candidate sites within the optimal zone, each exceeding 80 hectares, are recommended for detailed environmental-impact assessment. These findings provide Bogotá's Unidad Administrativa Especial de Servicios Públicos with a spatially explicit, stakeholder-informed framework for landfill-siting decisions.

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Weight: Distance from water vs Geology vs Flood risk vs Slope vs Population densityClose ×

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Introduction

Every day, Bogotá generates roughly 6,300 tonnes of municipal solid waste-enough to fill 630 dump trucks lined bumper to bumper along a 5 km stretch of the Autopista Norte [1] . Most of this waste ends up at the Doña Juana landfill, the city's sole operating disposal facility since 1988. Originally designed for a 20-year lifespan, Doña Juana has been expanded four times and is now projected to reach capacity by 2028 [2] . The search for a replacement site has been underway for over a decade but has stalled repeatedly because of community opposition, environmental concerns, and the inherent difficulty of finding a large tract of land that is geologically suitable, hydrologically safe, and socially acceptable in a metropolitan area ringed by mountains and protected watersheds [3] . GIS-based multi-criteria analysis offers a structured approach to this kind of complex spatial decision. By combining multiple suitability criteria each mapped as a spatial layer and weighted according to expert judgment-into a single composite score, MCA reduces the subjective element in site selection while making the trade-offs transparent and reproducible [4] . The analytical hierarchy process (AHP), developed by Saaty [5] , is the most widely used method for deriving criterion weights in environmental-siting applications and has been applied to landfill siting in over 50 published case studies worldwide [6] . Bogotá's situation is complicated by several features: the city sits at 2,640 m elevation on the Bogotá Savanna, a high-altitude plateau surrounded by the Eastern Cordillera of the Andes; groundwater resources in the savanna are heavily exploited for both municipal and agricultural supply; and the Bogotá River, which drains the entire metropolitan area, is already one of the most polluted waterways in Colombia [7] . Any new disposal site must avoid exacerbating these pressures. This research aimed to (1) develop a GIS-based suitability model for landfill siting in the Bogotá metropolitan area, (2) apply AHP weighting informed by local expert judgment, and (3) identify candidate sites within the highest-suitability zone for further evaluation.

Analysis was conducted at the Varanasi School of Natural Sciences, Uttar Pradesh, India [8] .

Scenario Development

Three weighting scenarios were developed to test the sensitivity of site rankings to different policy priorities. Scenario A ('Environment First') doubled the weights for distance-from-water and geology relative to the baseline, reducing weights on road access and population density. Scenario B ('Equity First') doubled the population-density weight to avoid siting near disadvantaged communities. Scenario C ('Cost First') doubled road-access and slope weights to minimize infrastructure investment. Under all three scenarios, the southwestern plateau retained its optimal classification, though Scenario B shifted the second-ranked zone from the northeast to the southeast to avoid proximity to low-income settlements. This robustness confirms that the southwestern plateau is a dominant solution rather than an artifact of a particular weighting scheme [9] .

Economic and Sustainability Assessment

A preliminary cost comparison was conducted for the two candidate sites (Site SW-1 and Site SW-2, each approximately 85-92 hectares). Estimated construction costs for a lined sanitary landfill with leachate-collection and gas-recovery systems ranged from USD 18.4 million (SW-2, flatter terrain) to USD 22.7 million (SW-1, requires more earthwork). Annual operating costs were estimated at USD 6.8-7.4 million based on per-tonne costs from comparable Colombian facilities. The benefit-cost ratio over a 25-year design life, including avoided transport costs relative to more distant alternatives, was 1.42 for SW-2 and 1.31 for SW-1. Both ratios exceed 1.0, confirming economic viability. A lifecycle greenhouse-gas assessment estimated that landfill-gas capture at either site could offset 34,000-41,000 tonnes of CO₂-equivalent per year, generating potential carbon-credit revenue under Colombia's national carbon tax framework [10] .

Materials and Methods

Materials and Methods

Materials

The research covered a 2,400 km² area encompassing the Capital District of Bogotá and portions of the adjacent municipalities of Soacha, Mosquera, Funza, and Sibaté. Spatial data layers included a 12.5 m ALOS PALSAR DEM for slope and flood-risk mapping, a 1:100,000 geological map from the Colombian Geological Service, a land-use map from the Bogotá District Planning Department (2021), road and hydrological network shapefiles from the Geographic Institute Agustín Codazzi (IGAC), and population-density grids from the 2018 National Census. Soil-type data were extracted from the IGAC 1:100,000 agrological survey. AHP weights were derived from pairwise comparisons by 14 professionals (engineers, planners, geologists) recruited from Bogotá's environmental agencies and universities. All GIS work was performed at the Department of Environmental Studies, Varanasi School of Natural Sciences, India [11] .

Methods: Each criterion was reclassified to a 1-5 suitability scale (1 = least suitable, 5 = most suitable) based on Colombian regulatory standards and international guidelines [12] . Exclusion zones (national parks, wetlands, airports, fault lines, 200 m buffer around surface water) were masked from the analysis. AHP pairwise-comparison matrices were checked for consistency (CR < 0.10 in all cases). The weighted linear combination was applied in ArcGIS Pro 3.1: S = Σ(wi × ci), where S is the composite suitability score, wi is the AHP-derived weight, and ci is the reclassified criterion score. The output was classified into five zones by natural-breaks classification. Sensitivity analysis varied each criterion weight by ±25% while holding others constant [13] . Zone A (Optimal) scores above 75 on all three dimensions, while Zone E (Excluded) falls below 25 everywhere. The gap between environmental and economic scores narrows from Zone A to Zone D, reflecting the trade-off between environmental safety and infrastructure cost in more remote locations.

Results

Results

Discussion

The concentration of optimal suitability in the southwestern plateau aligns with the findings of Rodríguez et al. [14] , who identified the same general area as favourable in an earlier, less detailed MCA study. But the present analysis adds three advantages: a finer spatial resolution (12.5 m DEM versus 90 m), a larger expert panel (14 versus 5), and the inclusion of flood risk as a separate criterion-an important addition given the catastrophic 1997 Doña Juana slope failure, which was triggered in part by saturated conditions on a floodplain margin [2] .

The sensitivity analysis showed that the optimal-zone ranking is robust to ±25% changes in any single criterion weight, but that simultaneous reduction of both distancefrom-water and geology weights can shift the optimal zone northward toward more geologically mixed terrain. This finding cautions against downplaying hydrogeological criteria under cost-reduction pressure [15] . Community acceptance, which was not modeled spatially here, remains the most significant non-technical barrier. Public engagement during the environmental-impact assessment stage should begin early and should incorporate benefitsharing mechanisms-such as local employment and community-improvement funds-to reduce opposition [3] .

Conclusion

GIS-based multi-criteria analysis identified 4.2% of the Bogotá metropolitan area as optimally suitable for new municipal solid-waste disposal, concentrated on the southwestern plateau where gentle slopes, clay soils, and distance from surface water coincide. Two candidate sites of 85-92 hectares each are recommended for detailed environmental-impact assessment. The AHP-derived weighting placed the highest priority on water-resource protection, and sensitivity analysis confirmed the robustness of the optimal zone under alternative weighting scenarios. For Bogotá, the practical message is clear: viable sites exist, and they can be identified through a transparent, reproducible, and stakeholder-informed process. But the window for action is narrowing as Doña Juana approaches capacity. Moving the two candidate sites from this desktop analysis to on-the-ground geotechnical investigation should be a near-term priority.

Acknowledgement

Acknowledgements Funding SourcesSupported by departmental research grants for environmental-planning research. Institutional SupportThe authors acknowledge the Department of Environmental Studies, Varanasi School of Natural Sciences, Uttar Pradesh, India. Contributions Not Qualifying for AuthorshipEnvironmental professionals in Bogotá participated in the AHP weighting exercise.

Figures and tables from the paper

Criterion	Weight	Rank	CR	Direction
Distance from water	0.214	1	0.047	Farther = better
Geology	0.187	2		Clay = better
Flood risk	0.158	3		Lower = better
Slope	0.134	4		Flatter = better
Population density	0.112	5		Lower = better
Soil type	0.082	6		Clay = better
Road access	0.064	7		Closer = better
Land use	0.049	8		Barren = better

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AHP Criterion Weights and Consistency Check

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Multi-criteria suitability scores for eight evaluation criteria applied to the Bogotá metropolitan area

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Composite environmental, social, and economic scores across five suitability zones.

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