life cycle optimization for waste management system
To reduce carbon intensity by 19% from 2010 to 2015, Tianjin’s waste management system needs an improved management method concerned the tradeoff between cost and greenhouse gas(GHG) emissions reduction. Most previous optimization analyses only focused on environmental impact except GHG emissions and cost respectively, but could not deal with the tradeoff between GHG emissions and cost. The aim of this study is to find a optimal solution for a waste treatment system which favorably balances the tradeoff between cost and GHG emissions reduction. The study takes waste treatment system of Tianjin, China as an example. First, based on the same case, six objective functions( cost minimization, GHG minimization , eco-efficiency minimization, cost maximization, GHG maximization and eco-efficiency maximization) were built and subjected to the same constraints. In addition, each objective function corresponds to one scenario. Second, GHG emissions and cost were derived from the waste flow of each scenario. Third, the range of GHG emissions and cost of the other potential scenarios were drawn, when the waste flow was adjusted by step size according to difference in above six scenarios. This range provides a comparative basis to determine an optimal scenario. The results suggest that 1) The scenarios located in the border between scenario min cost and min GHG created an optimum curve, and scenario min f2 has the smallest eco-efficiency in the curve. 2) Simple pursuit of eco-efficiency minimization using Fractional programming may be unreasonable. 3) Balancing GHG emissions from incineration and landfills benefits Tianjin’s waste treatment system as it reduces GHG emissions and costs.