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One of the most popular definitions of reverse logistics is stated by The European Working Group on Reverse Logistics (REVLOG) as in the following (De Brito and Dekker 2004): “The process of planning, implementing and controlling backward flows of raw materials, in process inventory, packaging and finished goods, from a manufacturing, distribution or use point, to a point of recovery or point of proper disposal”. As a result of increase in environmental consciousness in the society, issues related to reverse logistics have become more apparent in both academic and industrial environment. Besides that, environmental regulations which impose strict obligations have been enforcing on original equipment manufacturers (OEMs), governmental institutions, logistics service providers, municipalities and customers for decreasing environmental risks to keep sustainability in an expected level. Many regulations have been implemented such as European Union (EU) Directives 2002/96/EC and 2002/95/EC that are two of the most stringent regulations regarding to the waste of electrical and electronic equipment (WEEE) (European Parliament and of the Council, Directive 2002/95/EC 2002). The Directive consists of many regulations that help to increase value creation from WEEE by the help of recovery options such as remanufacturing, recycling, repair, and refurbishing.
In reverse supply chain and reverse logistics, collection costs are one of the significant contributors to the overall costs for end of life product management that should be minimized (Yüksel, 2009). Determination of product return processes and product collection centers are one of the critical and complicated decisions of reverse logistics and reverse supply chains which requires to handle managing planning and controlling activities of backward flows of used products and/or materials. Hence, location selection problem of collection centers has drawn much attention from both academic and business environment (Chou et al., 2008; Kapoor et al., 2008). It directly has impacts on long term profits and performances of organizations (Queiruga et al., 2008). In addition to these, it has a complex nature because it is hard to redeemable, difficult to reverse and implies a high degree of uncertainty (Snyder, 2006, Temur and Yanık, 2017). Decision making procedures in which multiple parameters are taken place can be grouped into two parts: (1) multi-objective problems which include an infinite amount of feasible choices, and (2) multi-attribute problems which include a finite set of choices (Cheng et al., 2002). Location selection for facilities is a multi-criteria decision making study field which is affected by much kind of performance metrics depending on decision makers’ preferences (Yang et al., 1997). Actors in a reverse supply chain may have various and multi-expectations; therefore, selection of the best appropriate location forces researchers to take into account conflicting ideas and perspectives simultaneously. In order to deal with conflicting criteria and complicated nature, resulting from subjective human judgements, of decision making, the fuzzy set theory is utilized in many industrial cases. In a classical set theory, it is thought that an element cannot be in and out of a set simultaneously. However, in the fuzzy set theory a fractional membership can be accepted. There is an extant literature on multi criteria decision making using fuzzy sets. Recently Pythagorean Fuzzy Sets are widely employed in calculating uncertainty. Although the literature presented a large number of valuable studies, according to the authors there is no study conducted on collection center location selection problem employing an integrated fuzzy approach (Pythagorean fuzzy AHP-VIKOR) to handle uncertainty and vagueness in such a complex decision considering multifaceted factors. This study contributes to the relevant literature by proposing a hybrid multi criteria decision model that handles linguistic uncertainties. A case study from Turkish e-waste recycling industry is conducted in order to verify the success of the proposed methodology. Depending on a large number of criteria and sub-criteria obtained from the extensive literature review and consulting to the decision makers, experts from academy and industry have evaluated different districts of Istanbul in order to determine the effectiveness of alternative collection locations for e-waste recycling process. In the view of these goals, the rest of paper is organized as follows: Section 2 describes the literature related to location selection in reverse logistics. Section 3 and 4 address an integrated fuzzy methodology composed of Pythagorean fuzzy AHP and VIKOR and a real-life application, respectively. In Section 5, the sensitivity analysis is performed while in Section 6, the study is concluded with the suggestions for future research.