Urban landfill site selection with combined environmental and socio-economic criteria in Naein County and estimation of its possible emitted biogas

The uncontrolled increase in population and the subsequent increase in urbanization have led to an increase in the production of various types of waste in urban areas. Although landfilling is the last choice in municipal solid waste management, it is still a common method for municipal solid waste management in developing countries. Due to natural anaerobic processes, landfilling in landfills causes the production of biogas and leachate, the type and amount of each depend on the volume, humidity, and type of waste. Leachate production in landfills can lead to health hazards, damage to plants, groundwater pollution, and the release of unpleasant odors. The aim of this study was to accurately locate the municipal landfill in Naein County by combining socio-economic and environmental parameters and also estimating the amount of emitted gas to evaluate the potential for energy recycling.

In this study, the AHP model was used to weight the criteria and L Satty quantitative scale was used to grade the priorities. For selecting the best spatial locations for landfills, first the location of municipal landfills in Naein County was chosen using environmental parameters. The potential of the area for the intended uses was evaluated by the WLC method, then using the TOPSIS method, spatial locations were prioritized based on socio-economic parameters and then the best spatial location was selected. Finally, the amount of emitted gas from the landfill in two conditions with and without leachate recycling was also modeled to investigate the potential of the landfill for energy recycling.

The results of this study showed that all the proposed regions for constructing landfills include the pixels with more than 0.8 usefulness in weighted linear composition maps. In the final options prioritization map, nine locations were identified, and the most suitable spatial location with the highest percentage of desirability was determined as the best place for constructing a landfill. The selected spatial location had the closest possible distance to the three most populous cities of the county. This location was located 24 km away from Naein. Also, the capacity of this location was several times more than the need of Naein County in the next 60 years, which is about 85 hectares, and if additional lands are needed, it can be expanded to the northwest. For other towns and villages with relatively large populations that are relatively far from the selected landfill, temporary waste collection sites can also be designated until the waste is eventually transferred to the main landfill site. The selected landfill location was also located 2 km from the main road. The results showed that the total amount of estimated emitted gas in each trench with leachate recirculation was equal to 4204.3 tons and without leachate recirculation was equal to 4448.9 tons. This indicates that if the leachate recirculates system is used, the total amount of gas emitted from the landfill will be about 6% higher than without recirculation. However, considering the amount of annual production waste in Naein and the rate of population growth, it is better to take steps towards the maximum amount of recycling and composting and the least amount of landfill as much as possible.

In this study, the results of combining both types of criteria (environmental and socio-economic) have led to the determination of the most desirable spatial location, which in addition to complying with environmental criteria from an economic point of view had the lowest cost. Also, according to the current population, the population growth rate of Naein County and the annual production of waste, it can be concluded that material recycling and composting production are more economic than energy recycling and biogas production.