# E-Waste Reverse Supply Chain: A Review and Future Perspectives
## 4 E-Waste Reverse Supply Chains
### Research on E-Waste Reverse Supply Chain Network Design Models  
RSC network design problems have attracted the most attention from companies and experts since it is one of the vital and challenging issues in the RSC environment [86]. The design of RSC network is great potential as an effective strategy to achieve the goals of companies [87]. RSC network design is strategic planning which is of key importance for the final ability of product recovery activities. Hence, the implementation of RSC network design aims to determine a proper network configuration for the flows of returned products [88]. The reverse chain of the used product normally comes from several locations and is incorporated at a few locations or even one destination. General RSC network structure, the proper physical locations, the number of necessary tiers, the number of centres needed, their maximum capacities, and transportation between nodes in the network need to be decided to transfer returned products from consumers to treatment facilities and to potential markets [89]. Several studies on the design of RSC network have been conducted for various sectors, such as sand [90], paper [89; 91; 92], plastic [93], vehicles [86; 94], carpet recycling [95], electronic waste [36; 96; 97]. There are two main types of objective function (i.e., cost minimization and profit maximization) considered in RSC models. Most studies investigated cost minimization as an objective function [36; 90; 91; 96; 98; 99; 100; 101; 102; 103; 104; 105] while a few research investigated profit maximization in their studies [89; 97; 106]. According to [PERSON] and [PERSON] [107], there are at least three key parties in any RSC network. The first one is collection facilities where customers can return their used products while the second party should be recovery centres including recycling and remanufacturing centres to process these used products. The last one is demand markets where can sell recovery materials. Based on the different types of returned products and various network designs, there are some other parties that participate in RSC networks, such as disassembly and disposal centres. In the literature of e-waste RSC modelling (as seen in Table 6), mixed integer linear programming (MILP) formulation is one of the common tools used [108; 109]. One of the early research was conducted by [PERSON] et al. [110] which aims to determine the way the used products being processed as well as minimize the total costs of the RSC network design using MILP. The model conducted a real case of a copier industry (especially HV02-machine) in Venlo in the Netherlands to demonstrate the usefulness of the model. Two candidate locations namely in Venlo (The Netherlands) and in Prague (Czech Republic) were examined. The study showed that there is a slight difference in costs incurred so the building of recovery operations in Prague should be selected from the view of the company. Two years later, [PERSON] [111] also optimized the design of RSC network for electrical devices and computers in Taiwan by utilizing MILP model. The overall costs considered in the model include shipping, operating, fixed, and disposal costs and the revenue from recovery materials. The quantity and the locations of storage areas, disassembly and recycling facilities were identified based on different take-back rates. The research found that the expansion of disassembly facilities for computers is not necessary whereas there is a need for a new disassembly facility for electronic devices as the returned rate increases by 20%. Similarity, [PERSON] and [PERSON] [112] proposed a recycling network design model for e-waste which aims to minimize the total cost of the recycling model under the capacity constraints. The study suggested that at pre-processing facilities, waste compression should be implemented since it is crucial for the whole recycling system. In addition, the uncertainty of the quality and quantity of used products should be considered in future research.