Application of Fuzzy TOPSIS for Evaluation of Green Supply Chain Management Practices (Case study: Zanjan Sepehr Khodro; Iran)

Despite the immense number of papers on green supply chain practices, proposing the most important practices of green supply chain management (GSCM) is less investigated. Consequently, this study aims to provide an incorporated process to find and rank the most important practices of green supply chain management (GSCM) for an empirical case study of Zanjan Sepehr Khodro (SKZ). Firstly, a systematic literature review is conducted to find the major practices of green supply chain management (GSCM). Next, three practices with their sub-criteria have been selected based on their frequency of application. These practices are then categorized based on the major perspectives of green supply chain management (GSCM). Finally, A Fuzzy TOPSIS methodology is applied to rank the green supply chain management (GSCM) practices and find their importance level in corresponding company. According to the results, the final rankings of practices are green recycling, green purchasing and green warehousing respectively.

re-investigated by [27]. Key indicators of external (Legislation, competitive, supply chain, societal) drivers, green materials coding, Green process management, Internal environmental management and cooperation with customers, green marketing, green market share, green supply chain management pressure (market regulatory competition), pollution treatment cost, ozone depleting chemicals, the degree of green collaboration with suppliers, collaboration between product designers and suppliers to reduce and eliminate product environmental impacts, green supply chain outcomes (environmental, economic, operational, intangible), recycling products processing ability, shipping documentation and reliability of delivery have been applied by [28], [29], [30], [31], [32], [33], [34], [35], [36], [37], [38], [39], [40], [41] and [42] respectively. As well as, the reference [43] invested on practices of pollution control initiatives, use of environment friendly technology, partnership with green organizations and suppliers, environmental certification, positive economic performance, decrease of cost for materials purchasing, decrease of cost for energy consumption, decrease of fee for waste treatment, decrease of fee for waste discharge, negative economic increase of investment, increase of operational cost, materials, operational performance scrap/ waste reduction, quality improvement, delivery improvement and capacity utilization improvement in a comprehensive research. Among all practices that reference [44] investigated, the following practice are more important to grasp GSCM which are; to redefine operation and production processes to ensure internal efficiency that can help to implement GSCM, redesigning and improving the product or service in environmental directives, reduction of hazardous waste, emission, etc., less consumption of e.g. water, electricity, gas and petrol, to install EMS and ISO 14000 series, providing environmental awareness seminars and training for stakeholders, advanced green production technology, to recycle, reuse and remanufacture material, use of cleaner technology such as energy, water and waste, sending in-house auditor to appraise environmental performance of supplier, process design and innovation and enhances R&D functions. GSCM researcher [45] emphasized on practices of providing consumers with information on environmentally friendly products and/or production methods, change to more environment-friendly transportation and taking back packaging between strategic KPIs, while [46] found staff environmental training more important practice than the rest. Recently, reference, [47] distinguished practices of commitment of senior management to GSCM, interfunctional cooperation for environmental improvement, compliance with legal environmental requirements and auditing programs, sale of excess stock or materials, sale of scrap and used materials, sale of used equipment (after buying new equipment).
To categorize above criteria, study refers to the literature. Practices of eco-design also called as design for the environment and green design (C1), design of products for reuse, recycle, recovery of materials, component parts (C2) and design of products to avoid or reduce the use of hazardous products (C3) are considered as sub criteria of green design by [47], [48] and [49] respectively. Eco-design also called as design for the environment and green design, includes activities that aim to minimize environmental impacts of products during their entire life cycle. Green purchasing includes activities that aim to make sure that the purchased items have desirable environmental attributes such as reusability, recyclability, and the absence of hazardous materials. The category of green purchasing includes sub criteria of buying environment-friendly raw materials (C4), choice of suppliers by considering the environmental criteria (C5), supplier environmental management system (EMSs) (C6) and environmental audit of suppliers' internal management (C7) applied by [50], [51], [52] and [53] respectively. As well as, re-manufacturing and lean production (C8), cleaner production (C9), to decrease scrap (C10) and improved capacity utilization (C11) are sub criteria utilized to construct indicators of GSCM in category of green production by researchers [54], [55], [56] and [57] respectively. Green production (C3) or manufacturing aims for continuous improvements of industrial processes and products to reduce or prevent pollution to air, water and land which results in the possibility of minimizing risks to humans and other species. Furthermore, green warehousing is taken into account by GSCM researchers of [58], [59], [60] and [61] which cover sub criteria of sale of excess inventories/ materials (C13), sale of scrap and used materials (C14), sale of excess capital equipment (C15) and environmentally friendly packaging (C16). In addition, among the green initiatives, green transportation received the least importance and just few studies have been executed in this category. In this study, the mentioned category is arranged by sub criteria of environmentally friendly transportation (C17) and environment-friendly distribution (C18) researched by [62] and [63] correspondingly. Finally, green recycling or reverse logistics include activities that aim at taking back products or materials for the purposes of reuse or recycling, remanufacture, repair, refurbishing, or safe disposal of the products and materials. This category includes two criteria of use of alternative sources of energy (C19) and Use of waste of other companies (C20) studied by [64] and [65] respectively.
In the current study, according to the literature, multiplicity of practices and their applications we have applied green practices of green purchasing, green warehousing and green recycling. Each of these practices covers some sub-criteria which are mentioned in literature.

Fuzzy sets and fuzzy numbers
In many cases, exact data is not adequate to model realistic situations and circumstances in our life, because human precedence is often subjective and uncertain and cannot be assessed with exact numerical values. Fuzzy set theory was developed by [66] to determine the complexity of human perception in order to project data by preparing mathematical effective nesses to solve ambiguity and uncertainties to enable partial set membership than the unstable set membership. Reference [66] were the first researchers to review the decision-making problem applying fuzzy sets, and presented the fuzzy multi criteria decision-making methodology for first time [67]. The study has applied triangular fuzzy numbers to estimate the preferences for its simplexes that let DMs to use it. A triangular fuzzy number is specified by (a, b, c) where a ≤ b ≤ c. The parameters a, b and c are the smallest possible, the most promising and the largest possible value respectively. In case of supposing X a group of items, known as the universe, and its elements are symbolized by x. in addition a fuzzy subset of X denoted by is represented by a membership function of ( ) f x A and is associated with each element x in A and a number between 0 and 1. A fuzzy set is defined by its own membership function as follow and is displayed in Fig. 1. Let A = (a,b,c) and B = (a1,b1,c1) be two triangular fuzzy numbers. Then the basic operations of triangular fuzzy numbers are defined as follows: The distance between fuzzy numbers A, B is calculated as: Assume that a decision group has K decision makers, and the fuzzy rating of each decision maker D k (k = 1,2,. . .,K) can be represented as a positive triangular fuzzy number k R (k = 1,2,. . .,K) with membership function Then the aggregated fuzzy rating can be defined as:

Methodology
TOPSIS is a classical method for solving MCDM problems. It was developed by [69]. The origin of TOPSIS is derived from the concept that the selected alternative needs to have the shortest distance from the positive ideal solution (PIS) and the farthest from the negative ideal solution (NIS) for solving a MCDM problem [64]. TOPSIS has a simple calculation procedure, systematic process and a reasonable logic that submit the rationality of human choice. It covers a wide range of practices (performance criteria) and causes transparent trade-offs between criteria meaning any changes in one criterion can be compensated by other criteria. Pair-wise comparisons, required by technique such as AHP, are avoided [61], [62], [60] and [55]. The TOPSIS method takes into account distances from the PIS and the NIS simultaneously by applying the definition of "relative closeness to ideal solution". Finally, the closest ideal solution to the PIS and farthest to the NIS is obtained. The TOPSIS solution method covers the following steps [65]: Step 1: The normalized fuzzy-decision matrix can be represented as: .
[r ] ij m n R  Where B and C are the sets of benefit and cost criteria, respectively, and , , Step 2: Weighted normalized decision matrix Step 3: The positive-ideal solution (PIS, A*) and negative-ideal solution (NIS, A−) can be calculated as [28]: 2 2 . .
Step 4: The distance of each alternative from PIS and NIS is calculated as: n Step 5: The closeness coefficient (CCi) of each alternative is calculated as: Step 6: At the end of the analysis, the ranking of alternatives is determined by comparing CCi values. Alternative Ai is closer to the FPIS (A*) and farther from FNIS (A−) as CC1 approaches to 1. The ranking order of all alternatives is determined according to the descending order of CC1.

A fuzzy multi criteria approach for green practices selection (calculations and discussions)
This study presents a practical example (Zanjan Sepehr Khodro) for application of fuzzy TOPSIS methodology to select the best green practices based on environmental criteria in a motorcycle manufacturing company. In order to access the mentioned goal, the aim of this study is to propose the fuzzy TOPSIS model for green practices selection and evaluation and to recognize the most important practices for our case study (Zanjan Sepehr Khodro) applying practical example.
Manufacturing operations have a main impact on environmental pollution during different stages of product life cycle, from resource extraction to manufacturing, use, reuse, recycling and disposal. Motorcycle manufacturing companies need to start to develop green practices over the manufacturing process to achieve ecological efficiency. This improvement is essential to access competitive advantages in the company's environmental performance. The proposed approach includes two steps of selection of evaluation criteria and the evaluation and selection of best practices using proposed criteria.
The first step involves the selection of criteria for evaluating the environmental effects of green practices. A comprehensive literature associated with GSCM was applied to select the needed practices. The needed criteria to be considered as base for our study have already been discussed and taken from internal customers (personnel) as follow. These criteria have been taken applying a simple questionnaire. According to the expectations of Sepehr Khodro' personnel, the study have selected 10 criteria to grasp which one of green practices is more important to satisfy the following expectations (criteria). It is worthy to say that Sepehr Khodro company includes different divisions as follow:  Administrative division  Assembly line division  Tire and wheel assembly division  Frame and bracket engraving division  Bracket clinching division  Inventory control division  Layout planning division  Quality control division  Auditory division The study have applied a survey distributed all divisions to figure out which criteria are more important for the company and finally has accessed the following Table1. A survey was directed through the distribution of a questionnaire between three experts of a motorcycle manufacturing company. Three decision makers were selected including an operations manager (DM1), a purchasing manager (DM2), and an environmental manager (DM3). These experts were selected from the company of Zanjan Matin Khodro. The respondents were asked to assign a score to each criterion to determine its importance and also to rank performance of company in three different specifications of green purchasing, green warehousing and green recycling independently. A seven-point Likert scale was used in the questionnaire to provide experts' opinions. The linguistic variable for rating ranged from 1 (very poor) to 7 (very good) and the importance weight of criteria varied from 1 (very low) to 7 (very high) are applied in Table 2 and 3 respectively. An excerpt of the questionnaire for evaluating environmental criteria is indicated in Table 4. (5,7,9) Good (G) (7,9,10) Very good (VG) (9,10,10) Table4. An excerpt of the questionnaire for evaluating environmental criteria Criteria Very low

Medium Medium high
High Very high Presence of hazardous materials Use of environmentally friendly technology Lack of environmentally friendly materials Use of hydraulic energy than the electrical one Commitment of personnel for GSCM Environmentally friendly packaging of purchased components Reusability of brackets, clinches and frames Use of waste of other companies Sale of scrap materials Weldability of scrap frame's subcomponents Table 5 indicates the fuzzy weights information resulted of assessment provided by the three DMs. In addition, rates of each of criteria for green practices of Sepehr Khodro, which are given by DMs, are shown in Tables 6, 7

Conclusion and future direction
The objective of the current study was to provide an comprehensive process to find and rank the most important practices of green supply chain management (GSCM) for an practical case study of Zanjan Sepehr Khodro. Firstly, a systematic literature review was conducted to find the major practices of green supply chain management (GSCM). Next, three practices were selected with their sub-criteria according to their frequency of application. These practices (green purchasing, green warehousing and green recycling) were then categorized based on the major perspectives of green supply chain management (GSCM). Afterward, A Fuzzy TOPSIS was applied to rank the green supply chain management (GSCM) practices and find their significance in associated company. According to the results, green recycling, green purchasing and green warehousing are ranked based on their significance respectively. The results lead motorcycle companies including both manufacturing and assembly to take better policies for their own management. These results help managers to prioritize their orders, as the importance of recycling is determined comparing purchasing and warehousing. Finally, the study proposes to the future researchers to invest on numbers of fuzzy numbers by developing these numbers, which will help to a better analysis of complicated problems with higher practices.