A BI-OBJECTIVE MATHEMATICAL MODEL FOR MUNICIPAL SOLID WASTE LOCATION-ALLOCATION PROBLEM: A CASE STUDY IN TEHRAN

There are different factors, including economic development and population explosion, causing the rapid increase in municipal solid waste generation rates. In today's municipal solid waste management, a considerable amount of financial and human resources is spent on collection and transportation, and little attention has been paid to production, storage in place, recycling, and disposal. As proper collection and transportation are important issues in municipal solid waste system, creation of energy from waste as well as recycling and disposal are also significant, attention must be paid to the optimal usage of dirty gold (i.e. municipal solid wastes) for pollution reduction. Moreover, determining suitable locations for transfer stations and waste disposal facilities is a very complex problem, needing a comprehensive review and evaluation process accounting for the requirements of municipal, environmental, and governmental regulations. In this context, it is vital to develop an effective and efficient approach for designing and planning a waste management system. In order to realize this goal, a three-level network consisting of customers, transfer stations, and disposal facilities (recycling, composting, wasteincinerator, and landfill centers) was considered in the present paper. A bi-objective mixed-integer linear mathematical programming model was presented for location and allocation of municipal solid waste. Model goals were minimizing waste disposal cost and greenhouse gas emission. Other points taken into consideration were a variety of products derived from recycling waste, transferring them to sales areas, and the limitations of number and capacity for transfer stations and waste disposal facilities. Districts 1 to 8 and District 22 of Tehran were selected as a case study for measuring model performance. The results of the case study and sensitivity analysis demonstrated that the optimal solution requires the location of disposal facilities in different districts of Tehran, although these facilities incur considerable costs.