Environmental dimension in sustainable supply chain management: Framework and literature review

The purpose of this study is to examine a sample of research works in order to highlight the existing gaps in the literature related to the environmental focus in sustainable supply chain management. Furthermore, the results obtained also provide researchers and practitioners with an integrative framework that helps easily fill lacks according to their area of study.


Introduction
*Until now, the literature discussing sustainable supply chain management (SSCM) has not drawn a specific study for the environmental focus yet, when it comes to the triple bottom line, the environmental dimension is simply acting a fundamental role in dealing with the whole SSCM. Moreover, literature has not claimed that the environmental dimension represents a set of practices and approaches to be implemented and developed to cover all the dimension, lots of researchers investigate the environmental side in SSCM by focusing solely on improving performance Govindan et al., 2019;Gómez-Luciano et al., 2018;Beske et al., 2014), or reducing risk Valinejad and Rahmani, 2018;Foerstl et al., 2010), and sometimes assessing impacts , and suggesting to follow the international standards in terms Seuring et al., 2019;, without making previously a preliminary and specific study for this dimension, that depends on the field of application, also on the studied part of the SC, which delimits the study and determines the crucial externs and interns factor to be considered. For instance, many studies admit that environmental focus is still regarded as for the main focus of the GSCM only Madani and Rasti-Barzoki, 2017), by attributing the word "green" to each part of the SC and linking environmental performance to green performance . In summary, works on SSCM should be aligned with the triple bottom line as integral elements in dealing with an SSC, also to cover all the gaps by promoting more studies and analysis in this sense.

The aim of the research
Based on the review of a significant number of articles, this paper is intended to answer the following research question: What is the environmental focus outlined in the papers dealing with the topic of SSCM and GSCM?
Our research motivation is to focus on the environmental dimension addressed in SSCM. Despite the considerable amount of research work, this topic is not sufficiently evolved Dubey et al., 2018), the objective of this research is to classify the set of research work according to criteria, to be presented as checklists, and to be used in the future as a database for researchers in this field. To meet the objective of this research, a set of research works is pinpointed, analyzed, and classified according to their field of application, the studied part of SC, context, target, and the environmental focus. Indeed, the main contributions of this work is to suggest an integrative framework, by proposing 12 relevant and persistent research gaps by section, as key factors to improve research in SSCM.
The contents of the following sections of this paper: Section 2 represents an overview of the SSCM, and then section 3 describes the research methodology. Section 4 discusses and analyzes the finding of this paper and gives a general framework of the environmental focus in SSCM, lastly, section 5 for the conclusion and some perspectives.

Overview of sustainable supply chain management
Over the last two decades, topics on sustainable supply chain management have been overstated in literature. And this, in light of the recently revealed world events, namely climate change, and technological evolution, in addition, these factors have explicitly contributed to the emphasis on the human factor, depending on economic factors. These three dimensions constitute the main axes of the SSCM. Among companies' relevant factors: Sustainability, hence the importance of considering both environmental and social factors in managing supply chain sustainability .
Many researchers have attempted to define the SSCM from theoretical and technical insights, (Gupta and Palsule-Desai, 2011) define the SSCM as a set of management practices that include: Environmental impact, the entire value chain for each product, product life-cycle. (Ahi and Searcy, 2013) through this paper, a set of definitions of SSCM and GSCM has been analyzed in order to propose a new definition of SSCM: "An SSCM is the creation of a coordinating SC, through the voluntary integration through the 3 dimensions: Economic, environmental, and social, based on key inter-organizational business systems designed for effective and efficient management of the 3 flows, including the 3 activities of procurement, production, and distribution, with the aim to meet stakeholder requirements and improve over the short and long-term: Competitiveness, profitability, and resilience of the organization." This definition takes into account the triple bottom line of economic, environmental, and social considerations. Knowledge management is among the factors that play an interesting role, in the sense of improving performance in SSCM, considering all attributes and the 3 dimensions .
Hence, performance is targeted by lots of researchers as the main purpose in achieving SSCM, some of them relate performance to reverse logistics and product recovery Govindan et al., 2019;Lim et al., 2017), while others combine sustainability performance with SC practices and the relationship between enablers, attributes, and stakeholders (Das, 2018;Foo et al., 2018;Esfahbodi et al., 2017;Diabat et al., 2014). In addition, literature is divided into two specific categories (GSCM and SSCM) that ideally converge towards an ultimate and common goal: To minimize the environmental impact of an SC. Thus, the rest of this paper aims to give an integrative framework of the environmental focus after analyzing the background literature.

Research methodology
A literature review framework was addressed in our study, relying on the rigorous approach  which suggests an integrative framework dealing with multi-tier modeling in SSCM, the paper analyzed the relevant literature, and then classified papers, and finally, it gave a description of the research gaps. The targeted output of our research is to fill and identify the knowledge gaps by presenting and cumulating the finding of different research work summarized as a map and a taxonomy that would help researchers and practitioners in the future. The metadata presented in this paper addresses descriptive statistics of popular journals, a field of application, countries that contribute a paper in this field, and the studied part of the SC, etc. A similar process model to Seuring and Gold (2012) is adopted, following the steps presented in Fig. 1.

Material collection
For this study, publications are uniquely selected from the database the web of science since it has adopted by academicians among indexing highquality content . We focused our research on rigorous studies on only the English language and also impact factor journal. For instance, we used as a keyword, key those replies to our research question in the first paragraph. For a period, we delimited our research from (2008)(2009)(2010)(2011)(2012)(2013)(2014)(2015)(2016)(2017)(2018)(2019), papers are selected according to each year, by screening and checking the adherence of the paper to the main topic, 2009 was excluded since no relevant paper, to our research, was found out this year. We used for our citation index the following linked keyword: SSC, SSCM, SCM, by using a combination of Booleans functions (such as: "SCM or SSCM"; "SCM and SSCM"), in both abstract and title from the main source of the type of article: Review article and research articles, and only English language paper are considered, also some relevant conference proceedings were taken into account. Metadata analysis was achieved by analyzing 132 papers derived objectively from the Web of Science database. Obviously, after screening titles and abstract first, then by removing duplicate and checking the full text, from 441 papers, only 132 papers dealing with SSCM were included. The result is presented in Fig. 2 each year.

Descriptive analysis
Papers constituting our research work are initially limited by year of publication. Search comprises those that have been published in 11 years (from 2008 to 2019 (May)) ( Figs. 2 and 3). Thus, most of the papers are published in the sixth recent years about 86%, from 2014, 2018 was notably the highest number of research work (31 papers, of which 25 are used in Appendix A, Table A1 of the sample), noticed that 2019 is treated in the first half, so the number is constantly increasing, which can be explained by the ever-increasing climate change resulting from SC. As the dominated journal "Journal of cleaner production" is number one in publishing article in this domain from our sample (31 papers), followed by the International Journal of Production Economics (13 papers), hereafter, Fig. 4 represents the top 10 journals of our sample. Regarding countries, India (12 papers) is the dominated country of publication of scientific works on SSCM, followed by Germany (11 papers), UK (11 papers), then China (8 papers), and Taiwan (6 papers) (Fig. 5).

Category identification
From 441 papers, we have classified 132 papers, which are relevant to our study, using filters (for each year) according to the keywords, also to related areas. From 132 papers, only 96 papers are selected as the sample of our research, and we used a table to classify them, although the other research works are also taken into consideration in the other sections. The categorical classification is done according to the categories (5 criteria (Fig. 6)) that best describe the purpose of this paper, namely:  Field of application: The field of application is among the indicators that better describe a topic; it's selected in order to fill the lack of research in each area of study, also to highlight the more addressed one.  The studied part of the SC: All the research works in this domain differ by the studied part of the SC, so it would be interesting to outline this criterion as well as to help researchers identifying some relevant papers for their research area.  Context: As for "the context of the paper," four categories are adopted to categorize our sample: "Modeling," "framework," "review," "analysis" N°of works N° of works since it appears that those categories are broadly consistent.  Target: Every research work has a specific target; this category is selected to illustrate the purpose of each paper in terms of the environmental focus.  Environmental focus: As the main purpose of our research, environmental focuses are identified from paper according to their objectives.
Furthermore, a detailed description of the four categories is addressed in the next section, with systematic analysis.

Result and discussion
This section is provided for the selected literature, papers are classified, as mentioned before, according to their field of application, the studied part of the SC, context, target, and the environmental focus in Appendix A, Table A1. A detailed description and analysis of the finding of this paper are addressed below, by classifying and drawing the gaps for each criterion, and then an integrative framework of the environmental focus is proposed.
Gap 1: Researchers must work collaboratively to standardize the environmental impact of the same field of SC, based on environmental analysis. Gap 2: To highlight the environmental impact, it is necessary to work on SSCM in other fields that contribute to environmental degradation (Climate change).

The studied part of the SC
The existing research works are very diversified in terms of the studied part of the SC, and some works deal with the whole part of SC, others focus on some specific parts such: Logistic (Ahmad et al., 2016), procurement , life cycle , decision-making , partnership , locationallocation (Ahmed and Sarkar, 2018), attributes Gap 3: To carry out a specific study (research work) on the sustainability of SC in relation to its suppliers in terms of environmental performance. Gap 4: To understand the relationship between SC practices and sustainability (environmental line). Gap 5: To conduct more research and studies on other parts of the SC in terms of sustainability (environmental line).

Context
Topics on SSCM are addressed in a varied way regarding the target of research work, also depending on the studied part of the SC. After analyzing the sample table, it is noticed that most of the work tends to model (58 papers), whether to optimize or evaluate or to identify a part or all of the SC, followed by the analysis context (53 papers), as there are some papers that combine two or three or even four contexts in the same paper. Particularly a set of papers cure the method of the survey to analyze the SSCM of a number of enterprises or a given sample, and in some case giving a framework to the SSCM. Table 1 summarizes all the papers of the sample according to their context. Transportation/transport Network Gap 6: To carry out a complete work that covers the four contexts (review, modeling, analysis, and then framework) in SSCM.
Gap 7: To make a difference between papers treating SSC or GSC: Management and modeling.

Target
SSCM include a wide range of area of study, based on the sample the object of the majority of paper is to study risk management in SSCM Rostamzadeh et al., 2018;Foerstl et al., 2010) factors influence SSCM(development, implementation, evaluation, integration), sustainability of SCM via suppliers, sustainability in SCM through different part, and SSCM performance/effectiveness Govindan et al., 2019;Tseng et al., 2019;Das, 2018;Gómez-Luciano et al., 2018;Dubey et al., 2018;Genovese et al., 2017) in other terms, there are some works that focus their study on: SSCM (policies, strategies, decision making, practices, innovation), while others in relating SSCM to different factors such: Customer awareness ; design Tseng et al., 2018) planning Reefke and Sundaram, 2017), enablers , stakeholders (Gold and Schleper, 2017;Esfahbodi et al., 2017), governance Esfahbodi et al., 2017;Govindan et al., 2016), and others tried through their research works to highlight the topic on leanness and greenness: Relation between SSCM and lean /GSCM, Green marketing  green HR

management etc.
Gap 8: To promote more research that gathers jointly the 3 dimensions, namely: Lean, green, sustainable, of the SCM. Gap 9: To explore the recent works in order to reach another relevant target in SSCM.

Environmental focus
The purpose of this paper is to highlight the environmental focus in SSCM; through the set of the identified papers, we tried to visualize the environmental part of the triple bottom line of the SSCM. The most common terms used in research work are Environmental: Criteria, dimension, orientation, factors, aspect, impacts, risk, assessment, performance, and sustainability. Furthermore, in terms of performance, it's noticed that works are divided into two categories: Environmental performance, and green performance, perhaps this difference is one of the reasons that have created the famous term "green supply chain"? We derived a set of environmental focus, as shown in Fig. 9 that classifies them into two main categories risk/issues, and performance:

Framework
The literature analysis shows a panoply of diverse way to discuss or treat topics of SSCM, the established framework is the first to be proposed in the literature in terms of criteria, gaps and barriers that tackle both GSCM and SSCM, also it's useful for future research works as key insights and literature background in this field. This framework presents the set of gaps in each section, and the related barriers, as shown below in Fig. 10.
The environmental focus is related to dispersed and non-similar paper targets, each research work focuses on a particular target, by selecting one or two contexts regarding the feasibility of the used tools or methods, independence to the studied part of the supply chain that is imposed by internal and external constraints, it is also limited by the field of application. The field of application derives from the environmental focus and may also depend on the information sharing, because, as discussed in section 4 and filled in gap 2, not all areas of application are covered in the literature in terms of environmental focus. The set of gaps is presented in Table 2, according to some references of the sample.

12
 To study and link environmental focus in GSCM and SSCM research works.

Conclusion
SSCM from a literal point of view is carried out in different ways, depending on the background or expectations of each researcher. Since it is a current subject linking two different concepts, namely SCM and sustainability, which were previously treated separately. In other words, the notion of sustainability is implemented as an essential criterion for an optimal SCM. Sustainability is, as known, involves together in the three dimensions: Economic, environmental, and social, except that practitioners of SCM always tend to give priority to the economic level. This dilemma recently has begun to reveal the importance of considering the triple bottom line, particularly the environmental dimension.
Hence, the environmental component is included in the SCM from several points of view; whether to improve the performance of the SC, minimize or optimize environmental impact, greening the SC, and even by following regulatory standards. The contribution of this paper highlights the environmental focus from a sample of different research works dealing with the SSCM. First of all, this study classified papers of the sample according to some criteria, such the field of application, targets; then in the basis of sample analysis, an integrative framework is suggested by proposing 12 relevant and persistent research gaps by section, as key factors to improve research in SSCM. This study mainly contributes to enhancing the environmental lack of SSCM in literature, which may help researchers and practitioners in the future.

Limitations
Despite the number of papers analyzed in this article, it is still not covering all the literature on this topic. So it turns necessary to state the limitations of this study as follows, to further enrich, and push forward research in terms of results:  To do the same work on the others database (e.g., SCOPUS);  To compare with more paper review and make an analysis;  To involve changes in keywords in order to cover all the existing literature, (e.g., Combining "green" with "sustainable");  To add another criterion in the papers' categorization.
Appendix A: The set of research works sample