With increased environmental awareness, a large amount of studies on green supplier selection has been promoted in the past decade. However the application of traditional impact assessments methodologies to fragmented and globalized supply chains is slowed down by provision of reliable data. Therefore, a comprehensive basis for Green Supplier Selection Model (GSSM) is proposed in this paper. In particular this paper proposes an index based on Life-Cycle-Assessment (LCA) to assess environmental burden of the whole company manufacturing activities. The resulting Company Environmental Performance Index (CEPI) can be used for sectoral benchmark to assess Company environmental Eco-Efficiency. The general methodology is presented with two strategic aims: the easy implementation of available data in standardized models and the reliable assessment of best performers within different manufacturing chains. Finally an application of such methodology to industrial cluster is discussed.