Landfill Gas Emissions and Air Quality Impacts in a Semi-Arid Urban Environment: The Case of Marrakech, Morocco

Greenhouse gases and air pollutants are continuously released from municipal solid waste landfills, particularly in rapidly growing urban areas where waste generation remains high. The Mnabha landfill is the main disposal site serving Marrakech, Morocco, yet the magnitude of its emissions and their atmospheric behavior remain insufficiently documented.

This study estimates methane (CH₄), carbon dioxide (CO₂), and non-methane volatile organic compound (NMVOC) emissions from the landfill and examines their atmospheric transport under local climatic conditions. Landfill gas generation was simulated using the LandGEM model, while a WRF–AERMOD modeling framework was developed to assess pollutant dispersion by incorporating regional meteorology, topography, and site-specific environmental characteristics.

The results suggest that landfill gas production is likely to reach its highest levels during the early 2040s. Methane, carbon dioxide, and NMVOC emissions are expected to peak near the end of the active filling period before gradually declining as waste degradation progresses. Dispersion modeling indicates a predominant northeast–southwest transport pathway, driven by the prevailing wind regime and the open terrain of the Haouz Plain. Elevated concentrations appear to remain concentrated within a few kilometers of the landfill, whereas lower and more diluted levels may extend over broader downwind areas.

Although modeled ground-level concentrations remain well below commonly referenced health-based thresholds, the continued release of methane and reactive organic compounds may still contribute to long-term climate forcing and regional air quality degradation. Sensitivity analysis identified the methane generation rate constant (k) and the methane generation potential (L₀) as the most influential parameters affecting predicted emissions. These findings highlight the importance of continuous monitoring, improved gas recovery systems, and site-specific emission assessments to support sustainable landfill management in semi-arid environments.