Sustainable supplier selection criteria classification for Indian iron and steel industry: a fuzzy modified Kano model approach

ABSTRACT

The aim of this work is to provide a systematic approach for sustainability criteria clustering into different useful categories. For this purpose, a methodology has been proposed with the following three steps. (i) A comprehensive set of the sustainability criteria in economic, environmental and social dimension has been extracted from the literature and have been customised for the iron and steel industry. (ii) A fuzzy Kano methodology has been used to classify these sustainability criteria into useful Kano cluster like must-be, one-dimensional, and attractive cluster (iii) further, must-be and attractive criteria derived from the second step were further sub-classified into three categories using Type IV Kano model. All steps have been examined in the iron and steel industry of India and findings indicate that quality and delivery criteria are classified as high must be criteria in the economic realm. Further, environmental and energy management system in the environmental dimension and social responsibility and right of stakeholders criteria in the social dimension are classified as high must be criteria. Prioritising must be and attractive criteria enable decision makers of other industries to select the appropriate criteria to adopt sustainability.

KEYWORDS:

• sustainability
• sustainable supplier selection
• fuzzy Kano model
• clustering
• type IV Kano model
• sustainable Kano cluster

1. Introduction

Growing customer awareness, stringent government laws and pressure from internal and external stakeholders have forced industries to adopt sustainability (Ahmadi, Petrudi, and Wang 2017). Achieving sustainability requires the integration of the Triple Bottom Line (TBL) attributes into their manufacturing process, manufacturing systems, and the entire supply chain. Sustainable supply chain helps industries to remain competitive and also supports industries to remain operational in the future (Büyüközkan and Çifçi. 2011; Azadnia et al. 2012; Tavana, Yazdani, and Caprio 2016). So, nowadays small, medium and large scale industries in India require a holistic view to adopting sustainability into their supply chains. Further, large scale industry such as the iron and steel industry has a significant impact on the TBL as compared to the medium and small industries. Being a large scale industry the extent of influence of this industry on sustainability dimensions is significant and its impact is threefold in economic, environmental and social dimensions: (i) colossal amount of finance is invested and also influence the economic growth of nation (ii) industry should have safe working conditions and provide good health facilities for its employees (iii) industry operations include excavation of minerals, emission of greenhouse gases, and disposal of wastes which impacts the environment. Therefore, achieving sustainability objectives in the iron and steel industry is inevitable.

Suppliers, as upstream supply chain partners play a vital role in the achievement of sustainability objectives of industry and help to achieve sustainability gains (Govindan, Khodaverdi, and Jafarian 2013; Luthra et al. 2017). Therefore, the selection of sustainability criteria for supplier selection in the supply chain is an important strategic decision (Bai and Sarkis 2010; Govindan, Khodaverdi, and Jafarian 2013; Fallahpour et al. 2017; Rao, Goh, and Zheng 2017). Zimmer, Fröhling, and Schultmann (2016) stated that researchers have mainly focussed on evaluation and final selection process as compared to the formulation of selection criteria for supplier selection. Basically, formulation of selection criteria is a fundamental step of the supplier selection process. From the sustainability perspective, decision-makers have to select the essential criteria for sustainable supplier selection in the social, environmental and economic domain. Hence, decision makers have to handle a large number of sustainability criteria for the evaluation of supplier’s performance and thus systematic clustering is required to identify criteria into each sustainability categories. To form the cluster, Kano model has been used by various authors (Wang and Wang 2014; Wang and Fong 2016; Shahin and Mohammadi Shahiverdi 2015; Pai, Yeh, and Tang 2018) in different fields like criteria for airline services, new product development for automobile sector, improving service quality of restaurants and attributes of smart cameras, etc..

In Supply Chain Management (SCM), Ghorbani, Arabzad, and Shahin (2013) have used Fuzzy Kano Model (FKM) to decide the weight of criteria for supplier selection in agricultural machinery manufacturing industry and authors have not used Kano model for criteria clustering. Further, for criteria clustering in SCM, Jain and Singh (2017) have applied FKM to make the Kano criteria cluster considering only economic dimension. However, criteria clustering in social and environmental dimensions have not been reported in the literature. From sustainability perspective consideration of criteria in all dimensions is essential to provide a better holistic view of supplier selection. This urges a need for a methodology to include supplier selection criteria in all sustainability dimensions and further classifies these essential criteria into appropriate categories and subcategories.

The aim of this work is to provide a systematic approach for Indian industries to classify sustainability criteria into appropriate categories and subcategories. For this, a fuzzy modified Kano model-based methodology has been proposed into three steps. In the first step, a comprehensive set of sustainability criteria has been identified from the literature and have been customised for the iron and steel industry. In the second step, a fuzzy Kano methodology has been applied to classify these sustainability criteria into different Kano categories (must-be one-dimensional, attractive and indifferent). Lastly, must-be and attractive sustainability criteria derived from the second step are further sub-classified into three categories using Type IV Kano model proposed by Shahin et al. (2013).

Classification into Kano categories has been accomplished by incorporating Kano philosophy in which the responses of the questionnaire are analysed (Kano et al. 1984). These responses are not always a true picture of the view of respondent and are often accompanied by vagueness and uncertainty (Jain, Singh, and Choudhary 2016; Ghorbani, Arabzad, and Shahin 2013). Therefore, to capture ambiguity and uncertainty in decision-makers, in this work a fuzzy Kano model approach has been adopted.

Subcategorisation of sustainability criteria within a category through Type IV Kano model helps decision makers to identify and focus on sustainability criteria which are most essential for Sustainable Supplier Selection (SSS). This sub-classification of must be and attractive sustainability criteria facilitate decision makers to handle fewer criteria which make sustainable supplier assessment more efficient. In the next section, we are going to review the relevant literature.

2. Literature review

2.1. Kano model

Kano model is a two-dimensional quality model based on the concept of customer quality developed by Professor Noriaki Kano in 1980. This model helps decision makers in knowing the level of satisfaction perceived by the customer when a product/service attribute is present or absent. Having a clear and better understanding of the relation between the level of customer satisfaction and product/service attribute, helps decision makers to improve quality of product/service as per customer requirements resulting in higher customer satisfaction level.

Kano model is a questionnaire-based model and utilises both functional and dysfunctional form of questions for each product/service attribute. Further responses are analysed with the help of 5 X 5, Kano evaluation table which classifies attributes into six Kano categories.

1. Must-be requirements (M): In this category, customer requirements which are essential and are necessarily needed by a customer in a product. As these requirements are taken for granted by customers in a product, hence fulfilment of these requirements will not increase the satisfaction level considerably; however, their non-fulfilment will increase the dissatisfaction level significantly.

2. One-dimensional requirements (O): From the customer’s perspective, fulfilment of these requirements is directly proportional to the customer satisfaction level, i.e. customer satisfaction increases if these requirements are fulfilled. However, nonfulfilment of these requirements results in a decrement of customer satisfaction level.

3. Attractive requirements (A): These requirements are not explicitly defined by customers and fulfilments of these requirements are also not expected by customers. However, upon fulfillment of these criteria, customer satisfaction increases manifolds but nonfulfilment of these requirements doesn’t bring dissatisfaction to customers.

4. Indifferent requirements (I): Customer satisfaction level is not influenced by the achievement or non-achievement of these requirements.

5. Reverse requirements (R): Customers do not prefer these attributes in the product and absence of these attributes increases customer’s satisfaction level.

6. Questionable requirements (Q): requirements with this rating designate that either the question was not phrased correctly, or the customer misinterpreted the question, or an illogical response was given.

Authors and researchers have applied Kano model in their work for classification of identified criteria or attributes into different Kano categories and results are mainly employed for new product development, selection of projects or finalisation of marketing strategies (Lee, Sheu, and Tsou 2008; Jain and Singh 2017). However, the scope of application of the Kano model is not limited to these areas only and Kano model has been applied in various domains such as service sector, automobile industry, supply chain management, airlines service improvement, e-health awareness, students satisfaction enhancement, project management, leadership style selection. (Salehzadeh et al. 2015; Löfgren and Witell 2008; Wang and Ji 2010; Mikulić 2007; Rashid 2010; Witell, Löfgren, and Dahlgaard 2013; Shahin et al. 2013).

Kano model has been integrated with other methods such as Quality Function Deployment (QFD),Taguchi method, Kansei engineering and various Multi-Criteria Decision Making (MCDM) techniques for determining the relative weights of the criteria (Avikal, Jain, and Mishra 2014; Llinares and Page 2011; Chaudha et al. 2011; Ghorbani, Mohammad Arabzad, and Shahin 2013).

In literature Kano model has been integrated with other methods for supplier selection. Ghorbani, Mohammad Arabzad, and Shahin (2013) proposed a Fuzzy Kano model based two-phase supplier selection process. Author has considered only economic criteria for the selection of suppliers. Jain and Singh (2017) proposed a fuzzy Kano model approach for supplier selection by identification of must be criteria in economic dimension. Jain, Singh, and Choudhary (2016) have developed a methodology for supplier selection based on attractive criteria in the economic dimension. In the proposed methodologies researchers have considered only economic criteria and social and environmental criteria have not been considered.

Although Kano model has been widely accepted by practitioners and researchers, the Kano model has certain shortcomings. First one is the compulsion for the respondent to mark only a single response each for a functional and dysfunctional form of question and secondly the Kano model does not capture the ambiguity and uncertainty in responses.

2.2. Fuzzy Kano model

Manski (1990) reported that human mentality and behaviour is accompanied by uncertainty and a traditional questionnaire are always over-interpreted. Further, Huang and Wu (1992) reported that customers cannot respond to their responses in a single answer. To overcome this uncertainty and vagueness in response from a respondent, Lee and Huang (2009) proposed a fuzzy Kano model. Unlike Traditional Kano model (TKQ), Fuzzy Kano model (FKQ) allowed the respondent to register multiple responses for a single question (Shahin, Barati, and Geramian 2017). A sample of TKQ and FKQ questionnaire has been exhibited in Table 1 and it is elicited that in TKQ respondent has the possibility of choosing a single response. However, FKQ incorporates fuzzy logic in the Kano model and provides the flexibility to the respondent of marking multiple responses for each question (Lee and Huang 2009). The response of functional and dysfunctional form of questions is summarized in two matrixes, M_P and M_N respectively.

${\mathrm{M}}_{\mathrm{P}}=\left\{0.4,0.6,0,0,0\right\}$

${\mathrm{M}}_{\mathrm{N}}=\left\{0,0,0.2,0.2,0.6\right\}$

Table 1. Traditional Kano model questionnaire (single and crisp response) vs. Fuzzy Kano model (multiple response).

		Like	Must Be	Neutral	Live with	Dislike
Functional form of question	Traditional Kano model	✓
	Fuzzy Kano model	40%	60%
Dysfunctional form of question	Traditional Kano model				✓
	Fuzzy Kano model			20%	20%	60%

As per Kano methodology requirement, M_P vector is transposed and is being multiplied with M_N row vector to get a 5 × 5 matrix which can be compared with Kano evaluation table for further analysis. The details could be seen in the work of (Ghorbani, Mohammad Arabzad, and Shahin 2013). Multiplication of M_P and M_N results into the formulation of matrix S as shown in Equation (1).

(1) $\mathrm{S}=\left[\begin{array}{ccccc}0& 0& 0.08& 0.08& 0.24\\ 0& 0& 0.12& 0.12& 0.36\\ 0& 0& 0& 0& 0\\ 0& 0& 0& 0& 0\\ 0& 0& 0& 0& 0\end{array}\right]$(1)

Elements of Matrix S are then compared to elements of Kano evaluation table for determination of the degree of membership of each criterion for different quality attributes. Elements of traditional Kano evaluation table has been exhibited in Table 2. After comparison with Kano evaluation table, membership degree for each quality attribute are summed and fuzzy set T is established as shown in Equation (2).

(2) $\mathrm{T}=\left\{\frac{0.36}{\mathrm{M}},\frac{0.24}{\mathrm{O}},\frac{0.16}{\mathrm{A}},\frac{0.24}{\mathrm{I}},\frac{0}{\mathrm{R}}\frac{0}{\mathrm{Q}}\right\}$(2)

Table 2. Modified Kano evaluation table.

	Dysfunctional form of question
	I like this feature omitted		I need this feature omitted		I am neutral about this feature		I can live with omitting this feature		I dislike omitting this feature
Functional form of question	Traditional Kano table	Type IV Table	Traditional Kano table	Type IV Table	Traditional Kano table	Type IV Table	Traditional Kano table	Type IV Table	Traditional Kano table	Type IV table
I like this feature included	Q	Q	A	A3	A	A2	A	A1	O	O
I need this feature included	R	RA3	I	Q	I	I	I	I	M	Ma
I am neutral about this feature	R	RA2	I	I	I	I	I	I	M	Mb
I can live with including this feature	R	RA1	I	I	I	I	I	Q	M	Mc
I dislike including this feature	R	R0	R	R	R	R	R	R	Q	Q

2.3. Type IV Kano model

Shahin et al. (2013) performed a critical review of the literature on Kano models and classified Kano models into three types on the basis of starting points and slopes of curves in Kano diagram. The author highlighted the shortcomings of previous types and proposed a new modified Type IV Kano model based on the life cycle concept of Kano categories. The new model has starting points of the curves very near to horizontal axis and within the indifferent area (Figure 1). Type IV Kano model further subcategorised, must be criteria into less must be (M_a), must be (M_b) and high must be (M_c) criteria and similarly, attractive category criteria are subdivided in to less attractive (A₁), attractive (A₂) and highly attractive (A₃) criteria. Kano evaluation table adopted for precise subcategorisation has been illustrated in Table 2. Further, in the next section sustainability criteria in the economic, social and environmental domain has been discussed.

Figure 1. Modified Kano model Shahin et al. (2013).

3. Sustainability criteria

Sustainable Development concept got its first real worldwide acknowledgement in 1972 at the UN Conference on the Human Environment held in Stockholm. Further, the 1987 Brundtland Commission report was submitted which emphasised the linking of economic development and environmental protection. 1992 Rio Declaration on Environment and Development, codified the principle of sustainable development and adopted ‘Agenda 21’, which ‘recognized each nation’s right to pursue social and economic progress and assigned to States the responsibility of adopting a model of sustainable development.’(Summit 1992).

Sustainability is a synthesis of economic, environmental and social development, a triple-bottom-line approach (Galankashi, Helmi, and Hashemzahi 2016; Seuring and Muller 2008). Government laws and improved stakeholders awareness about sustainable development have led industries to enhance sustainability achievement initiatives in their supply chains (Bai and Sarkis 2010; Jauhar and Pant 2017). Suppliers being an important supply chain partner of industry not only contribute significantly but can also play a major role in sustainability attainment for an organisation (Vinodh, Jayakrishna, and Girubha 2013; Kannan 2018). Hence, sustainable supplier selection process becomes a strategic decision for management and integration of economic, social and environmental criteria in the selection process is necessary. With this objective in consideration, identification of sustainable supplier selection criteria has been done for an iron and steel industry.

3.1. Economic criteria

In literature, it is evident that pioneer work in determining supplier selection criteria was done by Dickson (1966). The author reported 23 criteria along with their priority levels and this work has provided a base for many further types of research. Further, Weber (1991) provided a comprehensive view of criteria that were considered vital by purchasing personnel’s and academicians while selecting suppliers. The author reported that apart from Dickson criteria Just in Time (JIT) criterion has achieved considerable importance in the supplier selection process. Wilson (1994) conducted a research on selection criteria and reported that price criterion has become less important as stated in earlier studies.

Due to globalised markets and competitive market scenario, quality and service consideration criteria has gained importance and dominates price and delivery criteria. Verma and Pullman (1998) contradicted the fact that quality is the most important criterion for supplier selection and showed in their research work that cost and delivery performance are still the basis for selected suppliers. Cheraghi, Dadashzadeh, and Subramanian (2011) reviewed literature pertaining to selection criteria and presented Critical Success Factors (CSF) for supplier selection. The author reported a significant change in relative importance of traditional criteria (quality, delivery, price, service) and the emergence of nontraditional criteria such as non-traditional such as just-in-time (JIT) communication, process improvement, and supply chain management. Increased competition and globalisation of market aided by e-commerce were found to be the main reason for this change in relative importance.

Thiruchelvam and Tookey (2011) considered supplier selection as Multi-Criteria Decision Making Problem (MCDM) involving qualitative and quantitative criteria with tangible and intangible characteristics. These criteria are often conflicting in nature and a trade-off has to been made between them. Authors identified reliability, flexibility, environmental responsibility, process improvement practices as prevailing criteria for improving customer satisfaction. The time frame for a literature review of economic criteria has been taken as 10 years, i.e. from 2007 to 2017 except for the work of Dickson (1966).

From the literature review, initially, 34 criteria were identified. However, with the discussion with decision-makers, two criteria were identified to be of low significance, hence they were not considered and finally 32 economic criteria were identified (Table 3). During literature review, it has been elicited that different authors have considered same criteria with different notations such as “Quality “ criterion has been considered by authors as, ‘Quality Performance’, ‘Quality control’, Quality assurance’, ‘Quality management’, ‘Quality certification’. In this work, all criteria associated with Quality have been concatenated under criterion ‘Quality’. Further criteria such as ‘Financial health’, ’Financial performance’, ‘Financial stability’, ‘Financial strength’ has been clubbed under criterion ‘Financial position’. Similarly, ‘Cost’ and ‘Purchasing price’ has been covered by criteria’ Net price’ and ‘Services’, ‘After sales services’ has been enclosed under ‘ Repair Services’.

Table 3. Economic criteria for sustainable supplier evaluation.

Economic criteria	Supplier’s activity/action expected by industry for the achievement of the criterion	Beneficial/Non-Beneficial
Quality (E1)	The supplier should supply goods of high-quality meeting the quality requirements of the industry.	Beneficial
Delivery (E2)	Suppliers should deliver the right quantity of goods in the shortest possible time.	Non-Beneficial
Performance history (E3)	The supplier should have good past performance history in earlier contracts full filled.	Beneficial
Warranties and claim policies (E4)	The supplier should provide products to the industry with well-defined and valid Warranties and claim policies.	Beneficial
Production facilities (E5)	Suppliers are expected to have a modern production facility to full fill the contract.	Beneficial
Net price (E6)	The supplier should supply the raw material at a most competitive price.	Non-Beneficial
Technical capability (E7)	The supplier should have the ability to acquire modern technologies and technical resources for research and development practices and processes.	Beneficial
Financial position (E8)	The supplier should have a strong financial position and there should not be any interruption in supplies due to bankruptcy.	Beneficial
Procedural Compliance (E9)	The supplier for the industry should have an understanding of the compliance of the industry and should work accordingly.	Beneficial
Communication system (E10)	The supplier should have an open and transparent means of communication-basedon modern means.	Beneficial
Reputation and position in the industry (E11)	Suppliers should have a good reputation and should have good customer feedback, good and reliable business references.	Beneficial
Desire to do business (E12)	suppliers should have a strong and positive desire for business with industry.	Beneficial
Management and organization (E13)	The supplier should have a good understanding with management and should try to have a long-term relationship with industry.	Beneficial
Operating controls (E14)	The supplier should have clear operational Controls for controlling and managing the activities, processes, products, and services associated.	Beneficial
Repair services (E15)	The supplier should provide the repair services for product supplied in shortest possible time.	Beneficial
Attitude (E16)	Suppliers having the positive attitude can have a better and long-term relationship with the industry.	Beneficial
Flexibility (E17)	Suppliers should possess the flexibility to respond to short-term changes in demand and supply situations, external disruptions together with the adaptability in the new environment.	Beneficial
Geographical location (E18)	Suppliers should have a geographical location nearby the industry for fast delivery of the raw materials.	Non-Beneficial
Amount of past business (E19)	Suppliers with a large amount of past business are preferred as industry considers them to have a better reputation.	Beneficial
Training aid (E20)	Suppliers should have modern training aids.	Beneficial
Reciprocal arrangement (E21)	Suppliers should have reciprocal and contingency framework to have un irrupted supply of raw materials.	Beneficial
Reliability (E22)	Industries consider a supplier to be reliable when the supplier demonstrates the ability to meet performance expectations as set up by the industry. Hence reliable suppliers are preferred by industry.	Beneficial
Impression (E23)	Suppliers should have a positive impression on the industry.	Beneficial
Packaging ability (E24)	Suppliers should have good packaging ability while delivering the raw materials.	Beneficial
Professionalism (E25)	The supplier should have the expected level of competence and skill required for the work. The supplier is expected to conduct all the activities in a respectful, reliable and in a consistent manner which will preserve and strengthen the relationship with industry.	Beneficial
Process Improvement (E26)	Suppliers should have the ability to modify the manufacturing process needed in the future.	Beneficial
Product Development (E27)	The supplier should have the capability to contribute in the development of a new product along with the industry.	Beneficial
JIT (Just in Time) (E28)	The supplier should have the ability to work with JIT to reduce waste and inventory cost.	Non-Beneficial
Commitment (E29)	The committed supplier believes in the relationship with the industry and works to ensure that the relationship endures indefinitely hence suppliers should be committed for contract fulfillment.	Beneficial
Integrity (E30)	Suppliers should be honest and should show a high level of ethical behavior in business.	Beneficial
Long-Term Relationship (E31)	Suppliers should work with industry to have a long-term relationship with industry.	Beneficial
Political Situation (E32)	Suppliers should have the least political influence in the contract.	Beneficial

Further, discussion with decision makers team was done and industry expectations from the supplier for the achievement of each criterion were established along with the classification of criteria as beneficial or nonbeneficial. Criterion whose larger value is expected by industry has been classified as beneficial and criterion whose lesser value is preferred has been classified as a non-beneficial criterion.

It is elicited from Table 3 that only four criteria, Delivery time, Net price, Geographical location, and JIT has been classified as non-beneficial criteria and rest all criteria has been classified as beneficial criteria by decision makers.

3.2. Social criteria

Emphasis on social sustainability in form of poverty eradication, health and hygiene were first given in Conference held in 2002 at Johannesburg (Hens and Nath 2005). McKenzie (2004) defined social sustainability as ‘Social sustainability is a life-enhancing condition within communities and a process within communities that can achieve that condition.’ In some authors opinion, social sustainability is concerned about addressing of social issues like poverty, equity, education, wages, human rights, diversity, etc., for ensuring the long-term well-being of humanity (Mani, Agrawal, and Sharma 2015). Further, Littig and Griessler (2005) suggested three core indicators for the assessment of social sustainability. The first indicator deals with the fulfilment of basic needs to have a better quality of life. The second indicator relates to social justice to provide equal opportunities in domains such as education, employment, gender equity. The third indicator relates to social coherence, solidarity, and tolerant attitudes.

Nevertheless, the Triple Bottom Line (TBL) approach has three pillars of sustainability, the social aspect of sustainability is least addressed by scholars and practitioners (Mani et al. 2016). However, with increasing awareness about social sustainability issues among various stakeholders and also realising the long-term benefits of social sustainability, industries too have initiated efforts for achieving social sustainability in their supply chains (Mani, Agrawal, and Sharma 2015). In some authors opinion, social sustainability can be defined as the management of social resources involving people’s skills, relationships and social values (Sarkis, Helms, and Hervani 2010).

In literature, authors have identified different social sustainability criteria from various perspectives. Tavana, Yazdani, and Caprio (2016) identified four social sustainability criteria and through Quality Function Deployment (QFD) proposed three ways for attainment and assessment of these criteria. Amindoust et al. (2012) proposed a sustainable supplier selection process based on a fuzzy inference system taking into account the rights of employees and stakeholders, health and safety of workers and information disclosure as social criteria. Further, Rao, Goh, and Zheng (2017) proposed local community influence and stakeholders influence as social sustainability criteria. Azadnia et al. (2013) considered risk and social reputation as social criteria for sustainability for supplier selection. Govindan, Khodaverdi, and Jafarian (2013) proposed a fuzzy based multi-criteria approach for evaluating the performance of a supplier based on the TBL approach. In their work authors have employed four social criteria, i.e. employment practices, health and safety, Local communities influence and contractual stakeholders influence. Fallahpour et al. (2017) proposed a questionnaire survey based model for Iranian textile industry in which authors have identified: workers’ rights, health, and safety at work and support activities as social criteria and also considered sub-criteria for hybrid decision model formation. Spangenberg (2004) reported that there are four dimensions of sustainability, i.e. economic, the environmental, the social and the institutional one. The author examined the relationship between social, environmental and institutional sustainability objectives with the economic growth of the industry. Pourjavad and Shahin (2018) have identified Green design, Green purchasing, Green manufacturing and reverse logistics as the criteria for evaluation of the performance of green supply chain management. Baskaran, Nachiappan, and Rahman (2012) studied Indian textile industries for sustainability over six criteria in which social criteria considered are Discrimination, Abuse of human rights, child labour, long working hours and Society/unfair competition.

The timeframe for literature review was taken as 2009 to present and keywords for the literature review were, ‘social sustainability’ and ‘sustainable supplier selection’. Based on the literature review 17 social sustainability criteria have been identified relevant to the iron and steel industry (Table 4). During literature review criteria, ’Interests and rights of employee’ and ‘human rights’ were found to be same and hence were clubbed together. Further criteria, ‘Health and safety’, ‘Commitment to health and safety of employees’ were brought under the criterion ‘health and safety of employees’. Industry expectations from suppliers along with beneficial and non-beneficial classification have been presented in Table 4. Out of 17 identified sustainable social criteria,’ ‘child and bonded labor’ and ‘annual number of accidents’ has been classified as non-beneficial criteria with lesser the better value preferred.

Table 4. Social criteria for sustainable supplier evaluation.

Social criteria	Supplier’s activity/action expected by industry for the achievement of the criterion	Beneficial/Non-Beneficial
Social responsibility (S1)	The extent to which supplier contributes towards the welfare and interest of the society	Beneficial
Ethical issues and legal complaint (S2)	The supplier should do ethical practices and should not be under legal prosecution	Beneficial
Human rights (S3) (Interests and rights of the employee)	The supplier should safeguard the interests and rights of its employees	Beneficial
Rights of stakeholders (S4) (Involvement of stakeholders)	The supplier should provide the moral rights to all its stakeholders.	Beneficial
Health and safety of employees (S5) (Health and safety) (Commitment to health and safety of employees)	The supplier should ensure safe working conditions and provide medical and health facilities	Beneficial
Information disclosure (S6)	Suppliers should have an open disclosure policy regarding the raw materials, emissions, and hazardous material management for its stakeholders.	Beneficial
Respect for the policy (S7)	The supplier should abide by the laws laid down by the government and should respect the policies	Beneficial
Employment practices (S8)	Suppliers should not discriminate between employees on the basis of caste, gender, sex, race, color, national origin or disability.	Beneficial
Local community influence (S9)	The supplier should look after the health, education, service infrastructure, mobility infrastructure, housing, regulatory and public services, supporting educational institutions, cultural properties of the society.	Beneficial
Stakeholders influence (S10) (stakeholder relations)	The supplier at his end should have a procurement standard, consumer’s education, decision influence potential, stakeholder empowerment and stakeholder engagement.	Beneficial
Enterprise Resource Planning (ERP) system (S11)	Availability of ERP system at the supplier’s side which can enhance business performance, and helps in adhering to regulatory compliance.	Beneficial
Human resource capability (S12)	Skills (human, conceptual and managerial) enhancement practices through training and education activities carried out by suppliers for its human resource.	Beneficial
Child and bonded labor (S13)	Suppliers should not employ children for employment or practice bonded labor	Non-Beneficial
Wages (S14)	Suppliers payment of wages should be in accordance with the nature of the job and according to policies of the government	Beneficial
Society (S15)	Philanthropic activities took up by suppliers	Beneficial
Regulatory responsibility (S16)	Suppliers compliance to follow local regulatory laws	Beneficial
Annual number of accidents (S17)	The supplier should provide safe working conditions and should aim for zero accidents.	Non-Beneficial

3.3. Environmental criteria

The rapid modernisation of industries and technological up gradation of manufacturing processes of industries have resulted in increased production rates. Higher production rates resulted in excessive consumption of raw materials, Minerals, and various earth resources thus affecting the environment of the planet. To safeguard the excessive and greedy consumption of resources, the doctrine of sustainable development proves to be most relevant.

Ahmadi, Petrudi, and Wang (2017) defined environmental sustainability as ‘as meeting the resource and services needs of current and future generations without compromising the health of the ecosystems that provide them’. Having an understanding of the consequences and knowing the benefits, industries have initiated programs for safeguarding the environment individually or joining hands with suppliers. In literature, attainment of environmental sustainability by selecting sustainable suppliers by adopting sustainable supplier selection process is evident. (Zimmer, Fröhling, and Schultmann 2016) identified four environmental sustainability criteria for a telecom industry. Identified criteria by the author are a Green corporate social image, Eco-design, Environmental management system, End-of-pipe. Shen et al. (2013) advocated the need of giving attention to environmental criteria as a means to evaluate suppliers and proposed Pollution production, Resource consumption Eco-design, Green image, Environmental management system, Commitment of GSCM from managers, Use of environmentally friendly technology, Use of environmentally friendly materials and Staff environmental training as criteria. Lee et al. (2009) proposed a performance evaluation system for green supplier considering Green image, Pollution control, Environment management, Green product Green and Green competencies as the criteria. The author emphasised the need for a selection of the most appropriate supplier based on both the environmental protection issue and the traditional supplier selection factors. Chaharsooghi and Ashrafi (2014) proposed a model based on the extended model of the TBL approach for supplier selection using neofuzzy TOPSIS method. Author has considered Pollution production, Resource consumption, Environmental management system and Eco-design as the criteria. Amindoust et al. (2012) proposed a sustainable supplier selection based on Environmental Management System (EMS) and Environmental competencies as environmental criteria along with economic and social criteria. Luthra et al. (2017) identified EMS, Green Design and Purchasing (GDP), Green manufacturing (GM), Green Management (GRM), Green packaging and Labelling (GL), Waste Management and Pollution Prevention (WM), Environmental Costs (EC), Environment Competencies (ENC) and Green R&D and Innovation (GRD) as relevant criteria for selection of sustainable supplier selection for an automotive industry. Orji and Wei (2015) presented a modelling approach by integrating supplier behaviour information in a fuzzy environment with system dynamics simulation modelling technique. Authors have considered supplier behaviour with respect to environmental competencies (EC) and green design (GD) as environmental sustainability criteria and reported that a higher the investment in sustainability by the different suppliers, exponential will be the increase in total sustainability performance of the suppliers. Kannan (2017) reported 19 critical success factors for the selection of sustainable supplier selection in a textile industry.

Environmental criteria were searched with a time frame from 2009 to 2017 and 17 criteria were identified (Table 5). Criterion ‘Environmental management systems (EMS)’ encapsulated criteria such as ’environmental responsibility’, ‘environment adaptability’, ‘environmental competencies’, ‘environmental code of conduct’, and ‘environmental control certification’. Further, under criterion ‘Green technology’ three sub-criteria, i.e. ‘Green Research and Development’, ‘Green manufacturing’, and ‘Green process planning’ have been covered. In the criteria ‘Hazardous material management ‘, ‘Harmful chemical’, ‘Waste Material management’, ‘Waste Production’ and ‘Solid waste management’ criteria has been considered. Among the 17 sustainability criteria, four criteria have been classified as non-beneficial by decision maker’s team. The identified nonbeneficial criteria are, Greenhouse gas emission, Resource consumption, Noise, and Carbon footprint tax, and these criteria are preferred with lesser values. Further, in the next section, the step of the proposed methodology has been illustrated.

Table 5. Environmental criteria for sustainable supplier evaluation.

Environmental criteria	Supplier’s activity/Action expected by industry for the achievement of the criterion	Beneficial/ Non-Beneficial
Green Image (EN1) (Green corporate social image)	Efforts and activities took up by suppliers to reduce environmental impacts of operational processes,	Beneficial
Eco-design (EN2) (Green design)	Suppliers ability to supply a product which has maximum utilization of sustainable materials	Beneficial
Environmental management system (EMS) (EN3) (Environmental responsibility) (Environment adaptability) (Environmental competencies) (Environmental code of conduct) (Environmental control certification)	Extent of adherence to environmental policies and environmental certification like ISO: 14000	Beneficial
End-of-pipe (EN4)	Product/recovery initiatives by a supplier to collect them at the end of economic or useful life.	Beneficial
Pollution control (EN5) (Pollution production) (Pollution Prevention)	Initiatives taken up by suppliers for controlling of pollution and prevention of contamination of air, water, and soil.	Beneficial
Resource consumption, (EN6)	The extent of resource used by the supplier for producing the product such as raw materials, etc.	Non-Beneficial
Greenhouse emission (EN7) (Greenhouse effect)	The ability of the supplier to control and prevent the generation of greenhouse gases.	Non-Beneficial
Green Packing and Labelling (EN8)	Efforts showed by suppliers to produce a green product and environmentally friendly packing	Beneficial
Green warehousing (EN9)	Activities of the suppliers to cut down the costs and warehousing of materials based on carbon footprints.	Beneficial
Green technology (EN10) (Green R&D) (Green manufacturing) (Green process planning)	The capability of suppliers to use green technology to minimize the impact on natural resources	Beneficial
Green transportation (EN11) (Green logistics)	Supplier’s transportation means should have minimum environmental pollution contribution during contract fulfillment.	Beneficial
Energy management system (EN12) (Energy consumption)	Supplier’s initiatives for reducing energy consumption and the ability to adopt energy efficient methods.	Beneficial
Hazardous material management (EN13) (Harmful chemical) (Waste Material management) (Waste Production) (Solid waste management)	Availability of framework at suppliers ends for management (usage, collection, treatment, and disposal) of hazardous waste.	Beneficial
Recycling/Reuse/Remanufacture (EN14)	Ability of the supplier to rebuild the product with the use of reused and repaired parts.	Beneficial
Noise EN15)	The ability of the supplier to minimize the noise produced during the operational process	Non-Beneficial
Carbon footprint tax (EN16)	Financial penalty imposed over suppliers for emissions of each ton of GHG emitted	Non-Beneficial
Environmental training (EN17)	Training facility and practices carried out by suppliers for awareness of environmental conservation among employees.	Beneficial

4. Research methodology

The proposed methodology is developed for the classification of sustainability criteria into appropriate categories and subcategories. The proposed approach comprises of three phases consisting of seven steps (Figure 2):

Figure 2. Flow chart of the proposed work.

Phase I: Establishment of sustainability criteria in economic, environmental and social dimensions

• Step 1: Decision makers team formation

• Step 2: Identification and finalisation of economic, social and environmental criteria

Phase II: Fuzzy Kano methodology for criteria classification

• Step 3: Establishment of a fuzzy Kano questionnaire and response collection

• Step 4: Analysis of responses

• Step 5: Classification of sustainability criteria in Kano categories

Phase III: Sub classification of Must be and Attractive criteria using Type IV Kano model

• Step 6: Kano questionnaire for sub categorisation

• Step 7: Response collection and analysis

The proposed methodology is implemented as a case study for an Indian iron and steel industry. The detail application of the steps of the research methodology are as:

4.1. Decision makers team formation

Initially, a decision maker’s team comprising of eight personnel representing various departments associated with the supplier selection process is formed. Members of the team were selected from the top and middle management of the iron and steel industry. Team members have been selected from various departments such as materials management, finance, stores management, and quality control. All the team members have significant experience in their work and possess a thorough knowledge of supplier selection process of the industry. All the team members were personally contacted and prior consent of all the decision makers was taken for participating in the work. Details of the decision makers have been presented in Table 6. Team members were responsible for finalisation of sustainability criteria for the industry.

Table 6. Details of decision makers.

Decision maker	Department	Experience in years	Designation
Decision maker 1	Materials management	13	Senior manager
Decision maker 2	Materials management	21	Deputy general manager
Decision maker 3	Materials management	17	Assistant general manager
Decision maker 4	Materials management	9	Manager
Decision maker 5	Materials management	17	Assistant general manager
Decision maker 6	Finance	13	Senior manager
Decision maker 7	Stores management	17	Assistant general manager
Decision maker 8	Quality control	9	Manager

4.2. Identification and finalisation of economic, social and environmental criteria

Based on the literature review and with a discussion with experts from the iron and steel industry, initially, 72 sustainability criteria have been identified. After two rounds of discussion with the decision maker’s team, 66 sustainability criteria were considered for this work which comprised of 32 economic criteria, 17 social and 17 environmental criteria.

4.3. Establishment of fuzzy Kano questionnaire and response collection

Three separate FKQ, one each for economic, social and environmental criteria were established. A total number of questions in FKQ of economic criteria were 64 FKQ for social criteria comprises of 44 questions and FKQ for environmental criteria contained 36 questions. A team of Decision Makers (DM) was presented with these three FKQ. Before filling of questionnaire DM was briefed about the procedure and as an example response for ‘Quality ‘criterion was demonstrated. DM’s marked their responses in form of any numerical value ranging from 0% to 100%. At first, DM’s marked their responses for FKQ based on economic criteria followed by a FKQ based on social criteria and lastly, FKQ based on environmental criteria were filled. All the responses were collected and were checked for valid responses.

4.4. Analysis of responses

Responses to all three FKQ’s were acquired and the functional and dysfunctional form of questions were analysed. The response of all decision makers for Quality criterion has been presented in Table 7.

Table 7. Total level of the quality attribute for decision makers.

Decision makers	M	O	A	I	R	Q
DM 1	0.540	0.360	0.040	0.060	0.000	0.000
DM 2	0.680	0.170	0.030	0.120	0.000	0.000
DM 3	0.585	0.450	0.050	0.065	0.000	0.000
DM 4	0.640	0.160	0.040	0.160	0.000	0.000
DM 5	0.525	0.023	0.075	0.175	0.000	0.000
DM 6	0.488	0.263	0.088	0.163	0.000	0.000
DM 7	0.420	0.280	0.120	0.180	0.000	0.000
DM 8	0.455	0.245	0.105	0.195	0.000	0.000

4.5. Classification of sustainability criteria in Kano categories

Discussion with DM’s was held and a general consent was made for setting the threshold value as 0.3 for analysing the levels of the sustainability criteria. The consensus values are decided according to the rule:

1. Set value as one for all consensus values which are equal or greater than 0.3.

2. Set value as zero for all consensus values which are less than 0.3.

Applying these two rules consensus values are replaced by 1 and 0 depending on the values greater than or less than 0.3 and final values are represented in Table 8. Further, the frequency of Quality criterion has been calculated by summing up responses of all DM’s for each category. From Table 8 it elicits that for Quality criterion, highest frequency is of must be category. The frequency values for a threshold value of 0.3 follows the order M > O > A > I > R which is in accordance with the satisfaction level perceived (Pouliot 1993). Hence, considering the response of all DM’s, the Quality criterion has been assigned to must be Kano category.

Table 8. Classification of common consensus of decision-makers for the quality criterion for threshold value of 0.3.

Decision makers	M	O	A	I	R	Q
DM 1	1	1	0	0	0	0
DM 2	1	0	0	0	0	0
DM 3	1	0	0	0	0	0
DM 4	1	0	0	0	0	0
DM 5	1	0	0	0	0	0
DM 6	1	0	0	0	0	0
DM 7	1	0	0	0	0	0
DM 8	1	0	0	0	0	0
Frequency	8	1	0	0	0	0

Proceeding with the same methodology and applying the rules with a threshold value of 0.3, economic, social and environmental criteria for sustainable supplier selection process were classified into Kano categories.

4.6. Kano questionnaire for subcategorisation

A Kano questionnaire was developed based on the Kano model proposed by Shahin et al. (2013). The proposed model classifies only Must be and Attractive criteria further into subcategories. Hence, considering the sustainability criteria under these two categories a questionnaire was prepared and presented to DM’s team.

4.7. Response collection and analysis

The filled questionnaire was collected from the DM’s and was checked for valid responses. The marked responses were analysed with the help of the Type IV Kano evaluation table. The results of the analysis help in classifying must be sustainability criteria further as less must be (M_a), must-be (M_b) and high must be (M_c). The sustainability criteria under the Attractive category is subcategorised as: less attractive (A₁), attractive (A₂) and highly attractive (A₃). The proposed methodology has been implemented in form of a case study on an iron and steel industry of India, and the corresponding finding are presented in the next section.

5. Case study and findings

India is a developing country with a growing economy in which the iron and steel industry contributes significantly. In 2016, India was the third largest producer of Steel and in the February 2018 country has become the second largest producer of Steel in the world. Indian iron and steel industry has been prime manufacturers of rails, plates, wires, rods, wheel, and axels, etc., catering to the need for national and international customers. Being a large scale industry involved in steel production, the industry carries out many activities like excavation of minerals from mines, emission of greenhouse gases, and disposal of wastes in water and land which impacts all dimensions of sustainability adversely. Therefore, to have efficient and effective sustainable supply chain in the industry, sustainable suppliers need to be evaluated and selected. Thus, there is a need for identification and classification of the sustainability criteria for sustainable supplier selection for iron and steel industry in India. Fuzzy Kano model classifies sustainable supplier selection criteria into different Kano categories on the basis of the satisfaction degree associated with the criteria. Subclassification of sustainability criteria within a Kano category provides a better insight and understanding of the satisfaction level perceived by decision makers in the industry. The results of fuzzy Kano classification of sustainability criteria have been shown in Table 9. Further, the results of the application of Type IV Kano model for subcategorisation of sustainability criteria under must be and the attractive category has been presented in Table 10.

1. Economic criteria: It is elicited from results of fuzzy Kano classification of economic criteria that, Quality and Delivery have been classified under must be category signifying their importance in selecting a sustainable supplier. Iron and steel industry produces products which are being used in heavy structures like bridges and dams and need high-quality products for construction. Net price and technical capability as must be criteria emphasise that industry need their suppliers to supply goods at the most competitive price and should have the adequate technical capability. Examination of economic criteria in the one-dimensional category suggests that industry satisfaction increases with a reliable, flexible supplier having a sound financial position and good performance history having a close geographical location. Supplier’s needs support of suppliers for new product development and hence has been considered as an attractive criterion. Warranty policy of supplier and long-term relationship under attractive criteria category shows industry desire for a long-term relationship with their suppliers for smooth operations. Being a large scale industry it needs a favourable political support provision for training.

Table 9. Classification of sustainability criteria into Kano categories.

Kano categories
	Must be	One dimensional	Attractive	Indifferent
Economic criteria	Quality Delivery Production facilities Net Price Technical capability Repair services	Performance history Financial Position Communication system Reputation and position in the industry Flexibility Geographical location Reliability Process improvement	Warranties and claim policies Amount of past business Training Aid Reciprocal arrangement Packaging ability Product development JIT Long term relationship Political situation	Procedural compliance Desire to do business Management and organization Operating controls Attitude Impression Commitment Integrity professionalism
Environmental criteria	Eco-design Environmental management system Pollution control Green technology Energy management system Hazardous material management	Green image Resource consumption Greenhouse emissions Green packing and labelling Recycling/Reuse/Remanufacture	End of pipe Green warehousing Green transportation Carbon footprint tax Environmental training	Noise
Social criteria	Social responsibility Human rights Rights of stakeholders. Health and safety of employees Employment practices Stakeholder influence	Information disclosure Respect for the policy Ethical issues and legal complaints Local community influence Enterprise resource planning system Child and bonded labour Regulatory responsibility Annual number of accidents.	Human resource capability Wages Society

Table 10. Subcategorised sustainability criteria.

Kano categories
	Must be			Attractive criteria
	Less must be (Ma)	Must be (Mb)	High Must be (Mc)	Less attractive (A1)	Attractive (A2)	Highly attractive (A3)
Economic criteria	Production facilities Repair services	Net Price Technical capability	Quality Delivery	Training Aid Political situation	Warranties and claim policies Amount of past business Long term relationship	Product development JIT Reciprocal arrangement Packaging ability
Environmental criteria	Hazardous material management	Eco-design Pollution control Green technology	Environmental management system Energy management system	End of pipe Environmental training	Green warehousing	Carbon footprint tax Green transportation
Social criteria	Employment practices	Stakeholder influence Health and safety of employees	Social responsibility Rights of stakeholders. Human rights	Society	Wages	Human resource capability

Application of Type IV Kano model sub-classifies quality and delivery as high must-be (M_c) criteria. This specifies them as most prioritised criteria for SSS. Net price and Technical capability have been subclassified as must be (M_b) criteria followed by production facilities and repair services as less must be (M_a) sustainability criteria. Product development, JIT, Reciprocal arrangement, and packaging ability have been subclassified as highly attractive criteria (A₃) and their fulfilment will realise the highest satisfaction level for industries. Warranties and claim policies, amount of past business and the long-term relationship has been subclassified as attractive (A₂₎ and training aid and political situation as less attractive criteria (A₁).

1. Environmental criteria: Environmental management system and energy management system have been classified as must be criteria and industry wants its suppliers to focus predominantly on their fulfilment. Adoption of pollution control measures and green technology is an essential criterion for the industry. Industry satisfaction level increases proportionally when its suppliers adopt green product and packaging process, minimise greenhouse gas emissions and adopts recycling process in manufacturing hence these criteria have been identified as one-dimensional criteria by DM’s. Adaptation of green transport facilities by suppliers instead of conventional fossil fuel based transportation systems is difficult and hence is not expected by industry, but if suppliers are able to do will enhance the satisfaction level of industry. Carbon footprint taxation is highly attractive criteria for industry and wants its suppliers to control carbon emission in the environment.

In the environmental dimension, environmental management system and energy management system have been classified as high must be criteria (M_c) which signifies that industry is committed for the conservation of resources. Eco-design and pollution control have been subclassified as must be (M_b) criteria. Classification of carbon footprint tax and green transportation as highly attractive criteria (A₃) indicates that industry encourages its suppliers to adopt non-conventional energy sources.

1. Social criteria: Iron and steel industry employs a large number of human resource and influences the society significantly hence Social responsibility, rights of stakeholders and human rights have been classified as must be criteria. The industry is making efforts for the attainment of sustainability and for this is focusing on child labour policy, aiming for a lesser number of accidents and needs its suppliers also to take necessary measures at their end. Only three criteria out of 17 criteria are in the Attractive category, Human resource capability, Wages, and society. This signifies the fact that the industry considers social criteria fulfilment by its suppliers as an essential trait of the sustainable supplier selection process.

Social responsibility, rights of stakeholders and human rights are subclassified as high must be (M_c) criteria and clearly shows that industry is concerned about the social welfare of human resource. Health and safety and stakeholders influence have been subclassified as must be (M_b). Subclassification of human resource capability as highly attractive (A₃) criteria signifies that industry wants improvement in skill sets of employees for upgrading the quality of their life. Further, Wages has been subclassified as attractive (A₂) criteria and society as less attractive (A₁) criteria.

Results were presented to the DM’s team and discussion was held on the classified criteria under Kano categories. All DM’s were convinced and agreed to the classification. DM’s agreed that Quality is the most important criteria (high must be) for SSS and in industry quality criterion for the supplier is evaluated by three parameters: (i) Percentage of defective items supplied by the supplier. (ii) Capability of handling abnormal quality. (iii) Quality system certificates. Further DM’s shared information about assessment of delivery criterion. They articulated that delivery time and lead time of supplier are assessed under delivery criteria. Further, DM’s shared the fact that Environment management systems and energy management systems are essential criteria and are assessed on supplier certification for ISO 14001:2015 and ISO 50001:2011 respectively. During discussion DM’s informed that social criteria, Human rights and Social responsibility criteria of Must be category are focused upon by industry due to stringent government policies. Further, it was notified that human right criterion is assessed over the arrangements made by the supplier for freedom of speech and the right to collective bargaining for employees at supplier’s organization. However, a comparison of our findings with other relevant literature has been discussed in the next section.

6. Discussion

In this work Quality and Delivery has been identified as high must be, Net price as must be criterion and Production facilities and Repair services as less must be criteria. These findings are in line with the results of Dickson (1966) who reported Quality and Delivery criteria of extreme importance and Production facilities as criteria of considerable importance. Further, Weber (1991) also mentioned Quality, Delivery and Net price as vital criteria for supplier selection. Wilson (1994) and Cheraghi, Dadashzadeh, and Subramanian (2011) also reviewed supplier selection criteria and recognized these criteria as dominant criteria. Zimmer, Fröhling, and Schultmann (2016) reviewed sustainable supplier selection criteria and have reported quality, price and technical capability among the top 10 vital criteria for sustainable supplier selection. Hence, it evident that Quality, price, and delivery has sustained their vitality over the years and are still considered as an important criteria for supplier selection.

Results of this work elicit JIT, Reciprocal arrangements, Product development, and Packaging ability as highly attractive criteria. In past decades (1960–1990), Reciprocal arrangements have been considered as criteria of slight importance however due to advancements in technology this criterion has gained importance. JIT classified under highly attractive category in this work also resemble with the work of Cheraghi, Dadashzadeh, and Subramanian (2011) who reports JIT as a critical success factor for supplier selection. This transformation of JIT as such an important criterion could be owed to the fact that industries need to maintain an optimum level of stock and reduce the burden of inventory to remain competitive. Further, Warranties and claim policies are identified as Attractive criteria in this work and is in compliance with the finding of Kuo, Wang, and Tien (2010) and Guo, Yuan, and Tian (2009) who reported warranties and claim policies as a vital criterion in the supplier selection process. However, Dickson (1966) and Weber, Current, and Benton (1991) have addressed this criterion having an extreme importance. Political situation criterion is under the less attractive category in this work. The stable political situation of supplier’s country will attract industries for doing business and favourable business policies of the supplier countries will help to develop long term relationship between them. However, our findings differ from the findings of Zouggari and Benyoucef (2012) who reports Political situation criterion under risk category. Also, the Training aid criterion falls under the less attractive category in our work which is in contrast with the findings of Cheraghi, Dadashzadeh, and Subramanian (2011) and Thiruchelvam and Tookey (2011). However, in large scale and technology based industries training for managers and employees is considered as vital activity which is supported by the findings of Wu et al. (2016) and Kuo, Hsu, and Li (2015).

In environmental dimension, Environmental management system and Energy management system criteria are classified as high must be criteria in this work. This categorization fits with the findings of the Govindan et al. (2015) who reported Environmental management system criterion as primary criteria for selecting environmentally sound suppliers. Further, according to the work of Gurel et al. (2015) and Xia and Xu (2011), energy management system is essential for industries. Pollution control, Eco-design, and Green technology have been identified as must be environmental criteria and hazardous material management as must be and less must be criteria. These findings are in compliance with the reporting’s of Gurel et al. (2015) and Srivastava (2007). In this work Resource consumption and Greenhouse emissions are classified under one-dimensional category and which are among the top 10 preferred environmental criteria as reported by Zimmer, Fröhling, and Schultmann (2016). Many of the environmental criteria classified under must be and attractive category in this work assent with the environmental criteria considered by various authors for sustainable supplier selection (Chaharsooghi and Ashrafi 2014; Kannan 2018; Luthra et al. 2017).

The literature on review and analysis of social factors for sustainable supplier selection is scarce. However, the work of Ahi and Searcy (2015) and Zimmer, Fröhling, and Schultmann (2016) provide the necessary input for analysing the results of this work. Human rights, health, and safety, stakeholders influence along with an annual number of accidents have been classified as must be and one-dimensional criteria in this work. These findings are in compliance with the findings of Zimmer, Fröhling, and Schultmann (2016) who in their work have reported these criteria as the most preferred social criteria. Child and bonded labour criterion identified as one-dimensional criterion in this work is also vital from legislation perspective. However, it is not among the top 10 social sustainability criteria as identified by Zimmer, Fröhling, and Schultmann (2016). Stakeholder influence and Health and safety of employees are established as must be criteria in this work and have been reported by Husgafvel et al. (2015) as a major social sustainability performance indicator. Mani, Agrawal, and Sharma (2015) has performed a comparative analysis of supply chain social sustainability and reported human rights, health and safety, as salient criteria which are classified as must be criteria in this work.

6.1. Managerial implications

The focus of this work is to determine and classify sustainable supplier selection criteria and subclassify the criteria within the category for better prioritization of criteria. Difficulties in traditional Kano model has been overcome by implementing fuzzy version. Fuzzy Kano model facilitates the capturing of vagueness and ambiguity of respondents. Moreover, application of Fuzzy Kano model helps managers to have a clear insight of the responses which helps in better understanding of the requirements of the industry.

The proposed approach can be applied in various industries to help managers and decision makers to determine, classify and subclassify the sustainability criteria for the selection of sustainable suppliers. The classification approach in this work facilitates managers to determine the sustainable supplier selection criteria along with the dominant nature and level of satisfaction perceived on its fulfilment. The subclassification of must be category criteria facilitate DM’s to have a better understanding of sustainability criteria to focus primarily. The results help managers and practitioners to identify and prioritize the sustainability criteria for achieving a higher level of satisfaction in the SSS process which will also help in enhancing the sustainability in their supply chains. Further concluding remarks about work carried in this paper is presented in the next section.

7. Conclusion, limitations and future work

Sustainable suppliers facilitate industry in establishing sustainability in supply chains. Therefore, the selection and classification of sustainability criteria is an important issue for decision makers. Hence, there is a need of methodology which can classify the sustainability criteria into different categories on the basis of their significance and satisfaction perceived by their fulfilment. This research presents a comprehensive set of sustainability criteria for supplier selection and application of fuzzy Kano model for its classification into Kano categories (must be, one-dimensional, etc.). The proposed methodology further classifies the criteria within the category by application of Type IV Kano model. Findings of the methodology elicit that in the economic realm, quality and delivery are the high must be criteria. From the environmental perspective, environmental and energy management system and health and safety, human rights and social responsibility are high must be criteria in the social dimension.

The results of this work are vital for academicians, researchers, and supply chain managers of the iron and steel industry for the attainment of sustainability. The results of the proposed work are of significance as this work provides an insight into the classification and subclassification of sustainability criteria into different Kano categories. This better understanding of sustainability criteria through classification will help managers in selecting sustainable suppliers and thus can have better industrial practices which will help in achieving sustainabilty goals.

One of the main limitations of this work can be considered as the inability to assign quantitative weight to sustainability criteria classified under Kano categories. To overcome this limitation researchers are encouraged to integrate fuzzy Multi-criteria Decision Making (MCDM) methods in this work for weight assignment to criteria. Another limitation is that in this work, only criteria under must-be and attractive category have been focused for subclassification and criteria under one dimensional and other categories are not subclassified.

This work opens new avenues for researchers and academicians for future work. Researchers can develop a multi-phase sustainable supplier selection process by considering criteria from different Kano category at each phase of the selection process. For example ‘must be’ category criteria can be considered for initial screening phase and ‘one-dimensional’ category criteria for the second phase and ‘Attractive’ criteria for the final selection of sustainable suppliers. Further, decision makers from other industries can choose criteria from different Kano category in the economic, social and environmental domain to have a customized set of sustainability criteria for supplier selection. A practical extension of this work is to develop a sustainable supplier selection methodology integrating different fuzzy MCDM techniques and/or Fuzzy Inference Systems (FIS). Further, as future work of the proposed work researchers can formulate a mathematical model for order allocation to selected suppliers.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Notes on contributors

Naveen Jain

Naveen Jain is research scholar at National Institute of Technology, Raipur, India. He has completed his Bachelor of Engineering in Mechanical Engineering from Barkatullah University, Bhopal, India. He also holds Master’s degree in Production Engineering. His research areas are Supply Chain Management and Multi Criteria Decision Making (MCDM). He has published several papers in International and National journals and has presented papers in International Conferences.

A. R. Singh

Dr. A. R. Singh is an Assistant Professor in the Mechanical Engineering Department at National Institute of Technology, Raipur, India. He has completed his Bachelor of Engineering degree in Mechanical engineering from U.P.T.U, University, India. He has Master of Technology degree in CAD-CAM from Motilal Nehru National Institute of Technology, Allahabad, India. He holds a PhD in Mechanical Engineering from Motilal Nehru National Institute of Technology, Allahabad, India. His areas of specialization are operation research, supply chain management, optimization techniques and multi criteria decision making. He has published more than 30 papers in International journals and International/National Conferences. Some of the international journals in which papers are published include – International Journal of Advanced Manufacturing Technology, International journal of multi criteria decision making, Journal of intelligent manufacturing, International Journal of Design Engineering, International journal of manufacturing systems etc.