This paper describes the application of PROMETHEE-GAIA methodology in a multiple criteria analysis to rank potential environmental investments in mineral-processing companies. The intent of the paper is to identify best technical facilities on the basis of preferential relations between a set of variants. The method of Total Cost Analysis (TCA) was chosen to define the criteria. The economic and environmental costs, as well as the benefits of these technical facilities, were determined by means of this method. PROMETHEE is one of the methods in the Multi Criteria Analysis (MCA) category. The MCA, as the name implies, deals with the evaluation of a number of variants by several criteria. The technical facility was selected by a comparative analysis involving five influential parameters (Investment Costs, Annual Operating Costs, Operating Income, Administrative Costs and Disposal Fees, Economic and Environmental Benefits). As expected, the analysis resulted in a preferential ranking of these technical facilities.