This paper aims to solve a multi-period green supplier selection and order allocation problem with all-unit quantity discounts, in which the availability of suppliers differs from one period to another. The pro-posed approach involves three stages. In the first stage, decision makers use fuzzy TOPSIS (Technique forOrder of Preference by Similarity to Ideal Solution) to assign two preference weights to every potentialsupplier based on the supplier’s performance in two sets of criteria considered separately: traditionaland green. In the second stage, top management uses the analytic hierarchy process to assign an impor-tance weight to each of the two sets of criteria based on the organization’s strategy. The outputs of thefirst and second stages serve as inputs for a single-product bi-objective integer linear programmingmodel with deterministic demand that takes into account all-unit quantity discounts and a varying num-ber of suppliers in each period of the planning horizon. We implement the proposed mathematical modelin MATLAB R2014a software using the weighted comprehensive criterion method and the branch-and-cut algorithm. Statistical analysis helps determine the most suitable ranking approach for suppliers whentheir availability changes in each period. This paper presents a numerical comparison between two set-tings: the first considers all-unit quantity discounts, and the second does not. Moreover, a time studyshows that the proposed bi-objective integer linear programming model has an exponential computationtime.
