During the past two decades, there has been a growing concern on environmental issues around the world. Firms try to provide better production plans to recycle their used materials to reduce pollution from environment. In fact, lack of management in municipal solid waste for methods of collecting, disposal and processing of them can be significant damage to the environment, This paper presents a mathematical model for pet waste management, which plays essential role on municipal solid waste. The modeling formulation is a nonlinear probable mathematical programming model for chemical recycling the PET waste. In this model, the optimal amount of waste is determined by considering collected operations of reverse logistics and chemical recycling when demand is under uncertainty.