(587g) A Mixed Integer Programming Model for Municipal Waste Management and Landfill Gas-to-Energy Systems

The interest on the optimal management of municipal solid waste (MSW) has increased considerably due to technological and industrial developments. Several technologies have been developed as an attempt to address the problem of waste disposal from a waste-to-energy perspective. Apart from conventional problems associated to solid waste management (land space usage, high costs of transportation, groundwater pollution, etc.), methane emissions from landfill sites (Landfill Gas; LFG) represent an unresolved major problem. However, despite that environmental issue, landfilling is currently the best alternative for waste management in the developing world.

Mathematical programming approaches have been proposed to address many issues concerning waste management from various perspectives. As an extension to the existing approaches, this paper presents a mixed integer multiperiod approach to optimize a MSW network, considering waste reduction processes and landfilling. An original formulation is proposed to improve the economics of the landfill operation. The model incorporates an optimal LFG-to-energy design, which involves the installation of several harnessing technologies depending upon the annual increasing or decaying of the LFG flow rate. A direct-hauling system and an optimally located off-municipality transfer station are used to optimize the transportation of the MSW to the potential destinations. Actual data from a municipality in Mexico (Celaya, Mexico) has been used to define our case-study. The resulting Mixed-Integer Linear Programming (MILP) model has been solved through the GAMS® modeling environment. Our formulation has been assessed through several scenarios, including different LFG collection efficiencies and a bioreactor landfill operation. The minimum total cost of the MSW management is achieved through the installation of an LFG-to-electricity system and a materials recycling facility.

Keywords: Municipal solid waste management, mathematical programming, Landfill gas-to-energy.