Green Supply Chain Management: Conceptual Framework and Models for Analysis

: Sustainability and environmental concerns have been important topics of discussion in recent decades. Green supply chain management assures the effectiveness of public and company policies in greening their operations, increasing the market share, improving the company image and reputation, and increasing proﬁts. The objective of this article is to propose a conceptual framework that considers dimensions, categories, and practices in green supply chain management. After an extensive review of the literature, we identiﬁed models and a set of green dimensions, categories, and practices used for green supply chain management. From the analysis of the ﬁndings, we propose a conceptual framework that is organized into 3 environmental dimensions, 21 categories, and 64 green practices. The framework can contribute to the literature, given that empirical studies mostly select a limited set of dimensions to evaluate supply chain green practices. Finally, this study offers directions for future research.


Introduction
In the past few years, approximately 70% of the leading companies in their sectors have emphasized sustainability in their work agenda. Leading companies' reports reinforce that the success of their sustainability efforts also depends on the collaboration with the supply chain (SC) actors [1,2]. In this context, green supply chain management (GSCM) has contributed to the effective implementation of eco-efficiency [3], renewable energy sources [4], and sustainable actions [5] in the SC, in innovation clusters [6] as well as in symbiotic industrial networks [7]. Green or sustainable supply chain management (SSCM) involves integrating environmental and economic objectives into the management of the operation strategy of the supply chain. Such integration helps reduce the carbon footprint while increasing financial return and profitability [8]. A wider concept is SSCM, which aims to maximize profitability and, at the same time, reduce the environmental impact and improve the social well-being of the various involved stakeholders [9]. Ahi and Searcy [10] identified 22 different definitions for GSCM and 12 for SSCM. In this article, we use the term GSCM, despite recognizing the alternative use of SSCM [11,12].
Bowen et al. [13], p. 176, define GSCM as the "Integration of the company's purchase plans with the environmental activities in SCM, to improve the environmental performance objectives: Summarize recent research retrieving and interpreting similarities, themes, and issues on GSCM and contribute to the conceptual development of the theme and the future formation of a theory [34]. From a methodological perspective, the systematic literature review includes qualitative and quantitative aspects combined to evaluate structural and content standards. Therefore, the methodology used in this study follows the steps below [34]: combined with green operation, green practices, and green performance; − reading and selection of articles: the rough sample was entirely reviewed and a final, refined sample was identified; − complete review of the final sample and description of the structural elements of the articles: bibliometric description of authors, journals, and studies; − content analysis of the retrieved GSCM models for the identification of dimensions and categories of analysis; − evaluation of the content of the articles of the final sample; and − identification of similarities of dimensions and construction of the structure for the conceptual framework.
In the content analysis, we assessed models and classified green practices in GSCM according to dimensions and categories of analysis. Three external experts, two scholars from research institutes with experience in supply chain management and one scholar with previous experience in supply chains as a practitioner in the industry, participated in the analysis. The participation of specialists minimizes interpretation risks and subjectivities [34]. Finally, we constructed and proposed a conceptual framework for the management of green practices in SC.

Descriptive Analysis
Seuring and Müller [34] state that the first publications related to GSCM date from 1994. However, the main publications appear at the beginning of the 21st century and become significant from 2010 [35], the year of the beginning of the analysis. Table 1 shows the keywords employed in the search and the number of the roughly selected articles. Figure 1 represents the time distribution of the roughly selected articles. By the title and the abstracts, we selected a refined, focused sample of 43 articles with the greatest adherence to the purpose of the research. We read in full the entire sample prior to proceeding with the descriptive analysis. The descriptive analysis contributes to the identification of the models, the dimensions, and the categories of analysis of green practices [36]. The descriptive analysis of the sample considered the following issues: Who are the main authors? What are the main journals? What are the main existing models for managing green practices in SC? What are the dimensions and categories identified in the sample? How often are the categories referenced? Table 2 shows the three authors with the highest concentration of articles (individually or jointly) on GSCM and the main authors of the theme. The authors are also among the top 10 authors in the bibliometric review on GSCM published by Fahimnia et al. [35].  By the title and the abstracts, we selected a refined, focused sample of 43 articles with the greatest adherence to the purpose of the research. We read in full the entire sample prior to proceeding with the descriptive analysis. The descriptive analysis contributes to the identification of the models, the dimensions, and the categories of analysis of green practices [36]. The descriptive analysis of the sample considered the following issues: Who are the main authors? What are the main journals? What are the main existing models for managing green practices in SC? What are the dimensions and categories identified in the sample? How often are the categories referenced? Table 2 shows the three authors with the highest concentration of articles (individually or jointly) on GSCM and the main authors of the theme. The authors are also among the top 10 authors in the bibliometric review on GSCM published by Fahimnia et al. [35].

Models in GSCM
We identified six articles that consider complete and structured models for the evaluation of green practices in SC. We considered models that resemble a tree-like structure [37], that is, a top term supported by constructs that can be appraised by manifest variables or indicators [38].

Srivastava (2007)
The author reviews the literature on GSCM (approximately 1500 volumes, totaling 227 references). The author employed a tree-like structure, namely a top term (GSCM), 3 dimensions, and 14 categories, related to a set of green practices. As an early model, it has a certain amount of imbalance, as only two practices support the first dimension, the green design. Therefore, the author distributes the scope of GSCM into three main categories of analysis: environmental importance, eco-design, and green operations. Table 4 shows the organization of the dimensions and categories proposed by the author.

Seuring and Muller (2008)
The authors review 191 articles published between 1994 and 2007, which supported the proposition of a sustainable theoretical framework and a set of green practices for GSCM [34]. According to the authors, focal companies are responsible for the environmental and social performance of suppliers and distributors, encouraging extension in the adoption of environmentally friendly practices. The authors also mention that the discussion of GSCM goes beyond environmental management and should include economic and social aspects. However, in their sample of articles, environmental concern is the most referenced category, as shown in Table 5. The authors identified three main dimensions for GSCM: pressures, incentives, and barriers; green supplier management; and green product management. Table 6 summarizes the main points that support pressures, barriers, and incentives.  Table 7 considers the main points that support green supplier management. Regarding green product management, the authors include a discussion of firms' ability to make products environmentally friendlier, which includes eco-design and lifecycle analysis, aiming mainly at the reduction of waste and agility in disassembly and disposal.

Zhu, Sarkis, Cordeiro, and Lai (2008)
The authors propose a model that structures green practices into five blocks: internal environmental management, green purchasing, cooperation with clients, eco-design, and investment recovery [29]. The authors identify that the variables have significant correlations with GSCM. Table 8 shows the model that the authors propose with a measurement scale to evaluate the implementation of GSCM practices. The model was tested for its validity and reliability in the Chinese industry.

Testa and Iraldo (2010)
The authors analyze the determinants and motivators of green practice adoption and environmental and organizational performance. The study applied to 4000 organizations from different sectors in seven countries and tested whether GSCM positively influences environmental performance and the reputation of firms. The study classified the determinants into external and internal factors, related respectively to the pressures of the stakeholders and the company's business strategies [40].
Regarding external factors, the authors verify that three institutional mechanisms influence environmental decisions: normative, coercive, and mimetic. Normative pressures occur when clients ask to align firm strategy with customer demands and regulatory pressure. Coercive pressure occurs when stakeholders influence the dissemination of environmental reports. Mimetic pressure results when the development of environmental practices in specific sectors or competitive arenas becomes so significant that it induces their adoption by followers. Regarding internal factors, the three most observed motivations for the adoption of GSCM practices are reputation, which involves environmental performance, lifecycle analysis, green logistics practices, and cooperation with partners; efficiency, which involves the reduction of raw materials and energy; and innovation, typically led by a focal company.

Azevedo, Carvalho, and Cruz Machado (2011)
The authors identify the relations between green practices and SC performance. The study applied to five Portuguese automotive supply chains. The authors retrieve from the literature a set of green practices analyzed at three levels: upstream of the focal company, developed by and depending exclusively on the focal company, and downstream of the focal company [23]. Table 9 transcends the evaluation of practices at the focal company level but also considers suppliers and consumers. 3.2.6. Sellitto (2018) Sellitto [37] unified previous research. Sellitto et al. [8] propose a green practice management model applied to the Brazilian automotive chain. The study tested and refined a model to evaluate the effectiveness of GSCM implementation. Sellitto and Hermann [28] improved the model by adding a fuzzy-based decision method and implemented it in the agro-food industry. Based on those studies, the application was extended to other industries [37]. The model adopts a tree-like structure, formed by an overall concept (GSCM), supported by three constructs (Strategy, Innovation, Operation), that are also supported by 16 green practices. Table 10 shows the model.

Summary of GSCM Models
To synthesize the analysis, it is necessary to integrate the retrieved categories and concepts into a single model as simply as possible. To do so, it is important to summarize the main results retrieved from the studies and to propose a model. From a paired analysis of the dimensions and categories exposed by the models, we found similarities in the category levels and dimensions. Table 11 summarizes the objectives and main results identified in the models. Figure 2 summarizes the dimensions and categories observed in the retrieved models. Table 11. Selected studies related to GSCM.

Reference
Objective/Results [39] The article presents a comprehensive and integrated view of published literature in GSCM to facilitate study, practice, and research. The study proposes a structure based on three dimensions: the importance of GSCM, eco-design, and operations. [34] The article offers a review of the literature on GSCM considering 191 articles published between 1994 and 2007. The article also offers a conceptual framework to summarize the research in the field, comprising three parts: economic, environmental, and social dimensions. [29] The study evaluated the implementation of GSCM practices among manufacturers. The authors consider environmental management and cooperation in the strategic dimension, green purchases in the operations dimension, and eco-design in the innovation dimension. [40] The authors surveyed 4000 manufacturing companies to evaluate the determinants and motivations for GSCM implementation. They identified external and internal determinants. Strategic, innovative, and operational factors drive internal determinants. The study found that GSCM contributes to improving environmental performance. [23] The research identifies the influences of green practices in SC performance. The study was applied in the Portuguese automotive supply chain considering a set of practices and impacts at different levels of the SC. [37] The article tested and refined a model to evaluate the effectiveness of GSCM implementation in industrial SCs. The study assessed or estimated the effectiveness of green practices in SCs.
A considerable part of the categories is related to one or more authors. For example, eco-design is discussed by [23,29,34,37], Refs. [37,40] present three dimensions, while [39] introduces the operations dimension. The other authors did not introduce dimensions.

Identification of the Key GSCM Categories
The dimensions and categories mapped from the revised conceptual models helped to identify 21 categories and 3 dimensions. Table 12 relates articles to categories, analyzing the frequency of appearance. Eco-design, green purchase, and customer cooperation appear, respectively, in 84%, 56%, and 49% of the articles. A considerable part of the categories is related to one or more authors. For example, eco-design is discussed by [23,29,34,37], [37,40] present three dimensions, while [39] introduces the operations dimension. The other authors did not introduce dimensions.

Conceptual Framework and Green Practices
The information provided by the articles helped to define the framework categories. Subsequently, invited specialists reviewed the main concepts underlying the categories and aggregated similar ones (e.g., green design and eco-innovation were jointly framed as eco-design). The systematic review of the literature provided information and data, but the specialists' review guided and grounded the construction of the conceptual framework. Categories were organized considering their relationship with the dimensions and their relations and interactions within the SC (upstream, internal activities in the focal company, and upstream level). The specialists, together with the researchers, also classified 64 green practices retrieved from the literature in accordance with the categories.
Some of the categories can influence more than one sector of a typical SC. To deal with and illustrate this characteristic, the SC structure was separated into upstream (incoming materials and services), internal supply chain (the focal company and some small companies whose strategy is controlled by the focal company), and downstream (distribution and delivery materials and services) [23]. For example, the environmental strategy involves the three phases of the SC, supplier cooperation involves the first two, while customer cooperation involves the last two. Figure 3 shows the final conceptual framework, formed by 21 categories, 3 dimensions, and 64 green practices.

Conceptual Framework and Green Practices
The information provided by the articles helped to define the framework categories. Subsequently, invited specialists reviewed the main concepts underlying the categories and aggregated similar ones (e.g., green design and eco-innovation were jointly framed as eco-design). The systematic review of the literature provided information and data, but the specialists' review guided and grounded the construction of the conceptual framework. Categories were organized considering their relationship with the dimensions and their relations and interactions within the SC (upstream, internal activities in the focal company, and upstream level). The specialists, together with the researchers, also classified 64 green practices retrieved from the literature in accordance with the categories.
Some of the categories can influence more than one sector of a typical SC. To deal with and illustrate this characteristic, the SC structure was separated into upstream (incoming materials and services), internal supply chain (the focal company and some small companies whose strategy is controlled by the focal company), and downstream (distribution and delivery materials and services) [23]. For example, the environmental strategy involves the three phases of the SC, supplier cooperation involves the first two, while customer cooperation involves the last two. Figure 3 shows the final conceptual framework, formed by 21 categories, 3 dimensions, and 64 green practices.

Green Practices within the Categories of the Strategic Dimension
The strategic dimension includes 6 categories and 18 documented practices. Table 13 shows the practices allocated in the categories of the dimension and suitable references that provide empirical evidence of the application. . Compliance with quality standards; . Process design to avoid waste; . Lean principles to avoid overuse; Eco Design . Definition of components and raw materials ; . Definition of product components; . Product characteristics; . Energy use; . W a ste; Green Product . Design of products to avoid or reduce the use of hazardous products and/or their manufacturing process; . Design of products for reuse, recycling, recovery of material and component parts; . Design for resource efficiency; Organizational . Commitment of senior managers; . Support for mid-level managers and GSCM strategies; . Organizational strategy; . Multifunctional cooperation for environmental preservation; . Number of patents; . ISO 14001 certification; Green Marketing . Updating of company websites on environmental issues; . Adopting resource and energy conservation arguments in marketing; . Attracting customers with green initiatives and eco-services; . Providing customers with environmentally friendly service information; . Spending more budget on green advertising;

Green Practices within the Categories of the Strategic Dimension
The strategic dimension includes 6 categories and 18 documented practices. Table 13 shows the practices allocated in the categories of the dimension and suitable references that provide empirical evidence of the application. Table 13. Green practices in the categories of the strategic dimension.

Green Practices Activities Reference
Environmental plans and goals Environmental plans and objectives of the company that integrate the strategies of the organization and the supply chain. [21,57,63] Environmental risk management Adopting tools to assess, monitor, and mitigate environmental risks. [57,72] Environmental certification-ISO 14001 ISO 14001 supports the reduction of the consumption of raw material and waste and improves the quality of the products/services produced for customers. [20,23,47] Environmental audit program Monitoring national environmental compliance and audit programs. [16,46,47,61] Monitoring Monitoring the environmental performance of suppliers, including the second level. [23,34,46,47] Environmental accidents Developing actions to reduce environmental accidents.
[72] Benchmarking Sharing best practices with other members of the supply chain. [46,47] Support and education Supporting and training actions in the development of technologies that improve environmental performance and operation, and the adoption of environmental certifications. [34,47,54]

Joint ventures
The purchasing company works closely with its suppliers and establishes common teams and long-term joint programs to develop green innovations and solutions. [54,67] Eco-labeling Eco-labeling for the identification of environmentally friendly products. [45,51] Green packaging Actions that facilitate the recycling, reuse, and/or return of packaging. [23,43] Cooperation with suppliers and customers and cleaner production Valuing activities that result in eco-efficient processes. [29,72] Decreased consumption of hazardous and toxic materials Developing practices associated with lower consumption of hazardous and toxic materials. [43,73] Customer cooperation about environmental concerns Actions that value compliance with legislation, eco-efficiency, and the improvement of products and processes. [51]

Flow of information
Interconnected structures and systems that ensure the flow of information among supply chain stakeholders, ensuring competitive priorities related to company operations, quality, and customer satisfaction. [23,34,70] Sale of scrap, excessive inventory, and obsolete equipment Evaluating the processes considering the possibility of the sale, recycling, and/or reuse of scrap, sale of inventory, and obsolete equipment, transforming surplus or idle resources into revenue. [61,63,73]

Green Practices within the Categories of the Innovation Dimension
Green innovation supports environmental sustainability by promoting changes to processes with less environmental impact [40,52]. Product and process innovations are involved in energy saving, pollution prevention, waste recycling, green or corporate product design, and environmental management [20]. Table 14 shows the practices allocated in the categories of the dimension and suitable references that provide empirical evidence of the application.

Green Practices within the Categories of the Operations Dimension
Environmental costs, production, logistics, processes, purchasing, and the reverse logistics process characterize SC green operations. Table 15 shows the practices allocated to the categories of this dimension and suitable references that provide empirical evidence of the application.

Green Practices Activities References
Design of products Design that prevents or minimizes the use of hazardous and toxic products. [34,43,63] Design of products for reuse, recycling, or recovery of material and parts Designing modular products and easy-to-disassemble options that help to repair, recycle, and remanufacture end-of-life returns. [20,31,43,55,63] Design for resource efficiency Designing consumption-reducing products and energy. [4,31,54,63,73] Control structures Developing automated or error-proof control systems for defective parts or products. [6,20] Compliance with quality standards Adopting a standardized set of inspection criteria and quality standards. [20] Process design Designing processes that minimize or eliminate unnecessary movements, waste, and scrap. [5,68] Lean principles Analyzing the processes to identify activities and operations considered unnecessary and that do not add value to the final product. [6,20] Definition of components and raw materials Actions that reduce the consumption of material in production, use of materials that generate less pollution or waste, use of non-toxic materials, and use of recycled or recyclable materials. [31,53] Definition of product components Developing components with materials that can be recycled and derived from renewable sources. [34,53] Product characteristics Simplifying product characteristics, reducing weight and raw material consumption. [40,53] Energy use Using energy-efficient equipment and developing new processes, materials, and technologies. [4,7,40,56] Waste Minimizing waste generated in the production process, reusing waste, and ensuring acceptable limits of hazardous substances (compliance with emission limits). [39,53,69,70] Commitment of senior managers Leadership, commitment, and understanding of managers concerning the importance of GSCM to the organization and the chain. [5,25,42,46,61] Support for mid-level managers Manager education on green practices for the supply chain. [5,42,65] Organizational strategy Implementing GSCM in organizational strategy and integrating corporate policies. [25,34,65] Multifunctional cooperation Developing multifunctional groups with different expertise working in the analysis and evaluation of green practices. [67] Number of patents Research and development capability of innovations, facilitating new patents. [25,66] ISO 14001 certification Companies that implement ISO 14001 are likely to improve their internal environment through their network of suppliers and customers. [20,46,71] Updating of company websites on environmental issues Using websites to disseminate environmental reports and practices. [22,50,67] Adopting resource and energy conservation arguments in marketing Developing tools and technologies to make lifestyles more sustainable and encourage social change. [67,72] Attracting customers with green initiatives and eco-services Developing actions that influence consumers and industrial buyers through advertising that reflects the company's commitment to the environment. [22,67] Providing customers with environmentally friendly service information Developing services and practices that may result in actions that contribute to the environment. [67,72] Spending more budget on green advertising Investment incorporates complementary actions since companies gain a competitive advantage. [22,66] Products with environmental characteristics Alignment of the product development process with the consumer market and environmental issues. [8,53,66] Environmental management tools Developing environmental management tools for the supply chain to subsidize evaluation, monitoring, and the environmental quality of products and the cost of waste among the chain members.

Green Practices Activities Reference
Specifications for suppliers Providing project specifications to suppliers that include environmental requirements for purchases. [63,73] Green packaging Requiring suppliers to use environmentally friendly packaging (reusable, degradable, and non-hazardous). [5,49] Supplier selection Using environmental criteria to select suppliers. [66,73] Supplier audits Conducting audits to assess suppliers' internal environmental management. [5] Evaluation of second-level suppliers Assessing the environmental management of second-tier suppliers [5,34,49] Quality of internal service Using standards and criteria to monitor the internal quality of operations and services. [55,66] Cleaner production Developing methods and practical tools that protect human and environmental health to support sustainable development. [39,55,71,73] Inventory management Adopting methods and tools that allow inventory management. [42,44] Internal green production plan Planning the production, manufacturing, and resource allocation modules to apply environmental strategies. [44,66] Warehousing and green building Developing warehouse spaces conducive to environmental activities. [43,61] Packaging and documentation Enabling the use of packaging that can be reused, collecting packaging, and optimizing the return journey of transport structures. [43,53] Product distribution Optimizing the schedule and routing of deliveries of materials and components to the customer. [40,53,55] Remarketing Developing markets for remanufactured products. [20,67]

Returnable packaging
Encouraging the return of packaging for reuse and recycling. [23,24,30,49] Inspection and classification Classifying waste from production and consumption to facilitate subsequent activities. [39,73] List of substances Mapping the list of hazardous, toxic, and noxious substances for monitoring and control purposes. [63] Use of filters Using emission and discharge control filters.
[63] Solid waste Developing actions that support the reduction of solid waste. [23,67]

Carbon management
Developing plans and goals for reducing greenhouse gases.
[69] Water and energy consumption Reducing water and energy consumption in operations. [39,46] Risk prevention systems Employment risk prevention systems and environmental accidents/emergencies. [23,41] Hazardous and toxic materials Decreasing consumption of hazardous/noxious/toxic materials. [23]

Final Remarks, Implications, and Directions for Future Research
This study proposes a comprehensive conceptual framework that bridges the gap related to the need for effective models for GSCM. The conceptual framework considers dimensions, categories, and green practices identified in the literature. The proposed model can contribute to the literature given that empirical studies mostly select a limited number of dimensions to evaluate supply chain green practices.
The study has practical implications, mainly for service and industrial practitioners, managers, scholars, and government policymakers. Practitioners can use the results to implement management programs based on GSCM principles. Each category of analysis may provide guidelines for future implementation of green practices in SC. Practitioners can also use the prescribed model to assess the status of their SC regarding eco-efficiency, energy management, and other emergent issues regarding how manufacturing and service supply chains handle environmental issues. In handling our model of analysis, and supported by multicriteria techniques, managers can prioritize dimensions, constructs, and indicators according to the importance they demonstrate concerning SC strategic objectives. Scholars can use the proposed model for further in-depth studies, such as surveys in regional energy-intensive industries, waste producers, and various generators of carbon footprints.
Finally, governmental policymakers of regional development policies can use the model to stimulate the development of regional initiatives aimed at innovative industries. Public policies developed on the basis of our model may promote equality and development regarding environmental issues, mainly concerning service and manufacturing SC.
Although the article analyzes green practices in SC retrieved from the systematic review of the literature, the study did not consider other elements such as pressure and incentives that influence green practices and their results. Predominantly, green practices in SC will be more or less effective according to the presence or absence of enablers or moderators such as pressure and incentives.
The sample size of articles, 43 articles, is the main limitation of this study. A secondary limitation is the number of dimensions, practices, and categories identified. This number can increase with the social dimension, which will imply using other keywords besides the current "green supply chain management." From the study, we derive future research directions. As quantitative models to GSCM analysis use a limited number of dimensions, further research should introduce new dimensions. Examples of new dimensions are corporate social responsibility and networking operations. The proposed conceptual framework requires empirical studies on the dimensions and categories in GSCM through the implementation of case studies. Another area in which studies are needed is more surveys in entire industries. An example is the agro-food SC, since such an industry has a significant impact on the international economic and environmental scenario [74]. Over time, there have been a limited number of studies evaluating the adoption of green practices in agro-food SC [28,38,74], mainly regarding production [75], warehousing, and transportation [76]. Similar studies could be applied to research on emerging markets [18], e-business [77], e-commerce [78], and renewable energy industries [79].

Data Availability Statement:
No new data were created or analyzed in this study. Data sharing is not applicable to this article.