Integrated management of urban and rural wastes with energy recovery and low carbon emissions

Waste management is a major challenge worldwide due to the increasing amount of waste generated, which requires sustainable treatment approaches. In this paper, a mathematical model for the optimal configuration of waste treatment processes is presented that considers municipal solid waste and cattle manure from feedlots. A mixed-integer quadratically constrained formulation is proposed to maximize the net present value of investments, and a multi-objective optimization method through epsilon-restriction is implemented to limit the global warming potential. The model aims to resolve the trade-off between centralized and decentralized networks. The location of the facilities, the ratio of urban to rural waste for each facility, and the waste streams to be transported are also determined by the model. The optimization approach has been evaluated in a real-world scenario in Argentina. For integrated treatment, the results show the potential of anaerobic co-digestion that justifies transporting co-substrates from remote areas. Decentralized designs show that anaerobic digestion is only convenient for large cities and feedlot production sites. Economic and environmental benefits are significantly higher for the integrated alternative. Under optimized conditions, electricity price should be as high as 55.2 USD per MWh to reach the breakeven point from an economic perspective, assuming no revenues from carbon credits.