Waste production is inevitable in any society and consequently waste management is one of the main roles of any municipality. Therefore, it is necessary to evaluate different waste management scenarios. According to the amount and composition of the generated waste, considering environmental, economic and technical issues, several options are existed. Life Cycle Assessment (LCA) as a decision support tool has been used in several cases to select the most appropriate option. In this paper, production of greenhouse gases (CO2-CH4) in different waste management options in Mahdasht city (Iran) has been studied using IWM software and LCA application. Two scenarios has been defined, the first includes direct and complete transferring of waste to the landfill, and the second includes transferring of 76% of total waste to the landfill and recycling 20% and composting 4%. The questionnaires were fulfilled by the staffs and field surveying. The life cycle inventory cataloging was done using the IWM-1model according to environmental point of  view. The amount of produced greenhouse gases in the first scenario is about 9,218 tons and in the second scenario is about 6,801 tons. Results indicate that implementing recycling and composting operation can lead to the 26% reduction in greenhouse gas emissions and energy consumption reduction of a waste management system.