For the selection of the suitable place for the construction of sanitary landfill and biogas plant in the city of Najaf Abad, this study used fuzzy analytic hierarchy process, fuzzy analytic network process, and geographic information system. In this research, factors such as slope, aspect, geology, land use, biomass, and distance from groundwater, electricity network, protected areas, and roads were used as the most important criteria for site selection of biogas plant. The results of weighting and overlaying the maps of different criteria showed that based on the analytic network process, the best place selected for the establishment of biogas reactor was located in the southwest and based on analytic hierarchy process, the best places are located in the south and southwest of the study area. Suggested places, which are the best for the establishment of biogas plant, are located in barren lands of Najaf Abad. Moreover, according to the result, it is found that 10% and 11% of the study area are highly suitable based on fuzzy analytic hierarchy process and analytic network process methods, respectively. The results showed that the usage of fuzzy analytic hierarchy process, fuzzy analytic network process as multi-criteria decision-making methods in combination with geographic information system are suitable for selecting the best place for landfill and biogas plant.
