# E-Waste Reverse Supply Chain: A Review and Future Perspectives
## 1 Introduction  
Companies are currently challenged in globally competitive markets due to resource scarcity, environmental regulations, and economic pressure [1]. In addition, customers are becoming more demanding in terms of environmental and social issues [2]. Further, firms should take into account environmental regulations from governments to take responsibility for their end-of-life products. Some environmental regulations have been introduced such as the Waste Electrical and Electronic Equipment (WEEE) Directive, and the Restriction of Use of Certain Hazardous Substances Directive (RoHS) [3]. RoHS was introduced in the European Union and aims to restrict the use of specific hazardous materials found in electrical and electronic products, while the WEEE Directive focuses on reducing the disposal of waste and contributes to the efficient use of resources by re-using, recycling, and refurbishing [3]. These vital challenges are forcing companies to pay attention to reverse supply chain (RSC) management. RSCs or reverse logistics are terms used interchangeably in some literature [4]. An RSC consists of various activities to reuse or recycle a used product from a consumer or dispose of it properly. RSCs can be considered as one of the most vital ways to implement circular economy practices at an inter-organisational level [5]. An RSC is also part of a closed-loop supply chain which is the combination of forward and reverse flows of products and information in the supply chain that circulates an on-going flow of products. With the significant amount of upgrading of electronic devices, electronic waste (e-waste) is one of the fastest-growing types of waste. For example, 80% of mobile phones have been upgraded every two years, which leads to a large number of discard products [6]. E-waste RSC systems require a unique system from general RSC systems due to e-waste containing some special characteristics and features, such as a short product lifecycle, and the large amount of precious and hazardous materials involved [7]. The complicated processes of RSC for e-waste comes from the disposal of e-waste. It is a dynamic system with a high level of uncertainties in quantity, quality, and time of returned products [8]. Firstly, there are three main sources of e-waste generation, including households, industries, and institutional sources (i.e., schools, hospitals, and governmental agencies) [7]. Secondly, e-waste collection is derived from municipality collection points, electronic industries, retailers, and informal and formal recycling sectors. Informal recycling activities are common in developing countries, such as India and South Africa, where recycling methods are rudimentary, and a significant proportion of e-waste components end up in uncontrolled landfills. To mitigate the amount of product disposal, industries have been carrying out 6R concepts (namely, Reduce, Reuse, Recycle, Recover, Redesign, and Remanufacture) to improve recovery implementation and minimize non-value added activities within end-of-life (EoL) management [9]. Companies gain many benefits by implementing product EoL treatment, such as financial benefits to companies, product usage, increasing market share, improved public reputation, and competitive advantage. The amount of published research in the field of reverse supply chains focusing on electronic waste is significantly increasing. However, the number of review papers on e-waste RSCs is still limited. To fill the research gap, this research aims to provide a comprehensive picture of the area by reviewing the literature and classifying it into four key research types: factors of implementation, performance evaluation and decision making, foresting product returns, and network design. After reviewing the published articles, research gaps and the potential works were then identified and suggested for future researchers. The rest of the paper is organized as follows.