Green Logistics Instruments: Classification and Ranking

1. Introduction

The functioning of supply chains a set of processes of procurement, production, and distribution of material flows to the final consumer. The classical concept of supply chain management synthesizes the tasks of logistics – minimization of total costs in the chain, operational management – effective inventory and production management, marketing - focus on creating value for the customer [1]. However, the intensive spread of such concepts as Sustainable development, Triple Bottom Line, ESG (Environmental, Social, Governance) all over the world is changing views and approaches to supply chain management. Along with the economic benefits of companies, the policy of people's welfare and environmental protection are an integral part of supply chains management (SCM) nowadays [2]. Companies around the world are implementing green practices in supply chain management, trying to transform supply chains into sustainable supply chains or green supply chains. National governments and company management are implementing various programs and projects to achieve sustainability goals. Green or sustainable supply chain management is one of the most relevant topics in modern research of operations management, logistics, and sustainability [2,3].

The analysis of papers in the field of green or sustainable supply chain management shows an increase in the number of scientific papers devoted to theoretical and practical problems of implementing green practices. The existing approaches can be divided into two groups. The first one is related to the research of supply chains as a single system [4,5,6], the second one is related to the research of individual green operations [7] or elements of supply chains. The latter include, for example, studies of sustainable supply [8,9], sustainable production [10,11], sustainable warehousing [12,13], sustainable transportation [14,15], sustainable consumption [16]. One of the key research questions is the challenges of implementing green solutions and practices in logistics. Such practices encompass the integration of sustainable approaches into forward and reverse logistics operations to promote balanced social, environmental and economic performance [3].

The main objective of our study is to categorize the currently used green solutions and practices in logistics activities to develop a universal system of green logistics instuments. This study makes both theoretical and practical contributions to the field of green logistics and green supply chain management. Firstly, based on the analysis of scientific publications and structural-functional approach, we have identified green solutions and practices and developed a universal system of green logistics methods and instruments. The main idea of the classification is to compare and group different green solutions and practices with the functions of structural (logistics) elements of green supply chains. Second, we developed a methodology to rank green logistics instruments in the supply chain using multi-criteria decision-making (MCDM) techniques. This methodology will help stakeholders make effective decisions to implement green logistics methods and instruments in supply chain elements based on the ranking of instruments.

The rest of the paper is as follows. The next section contains the literature review. The third section describes the methodology for systematization and ranking of green logistics methods and instruments. The fourth section presents a computational case study of the implementation of the proposed methodology. The last section contains the main results and directions for future research.

2. Literature Review

To understand the terminology used in relation to green practices in logistics and to identify the most common keywords, we used a combination of keywords to search for review articles in Scopus: “Practices” AND “Review” AND “Green AND supply AND chains” OR “Green AND Logistics” in their titles, abstracts, or keywords (Figure 1).

The analysis of articles indicated that different terms are used in the research in relation to green practices: Criteria, GSCM practices, Factors, Measures, Green logistics practices, Activities, Initiatives, Drivers, Practices, Green practices, Green activities, Decision, Attributes, Sustainable practices, Solution, Policies, GSCM initiatives, Green logistics activities, Green initiative.

We have analyzed review papers in which the authors have attempted to group and systematize various green solutions and practices as applied to supply chain and logistics activities.

The paper [17] compares green and lean practices on supply chain management performance. The authors grouped 17 practices into two groups and presented their brief characterization of the practices. The 14 solutions are grouped into 4 types of activities: Green office, Inventory control and material handling, Green warehousing and Green transportation [18]. The authors in [19] identified three levels of dimensions and categories for different green activities and operations aimed at improving the efficiency of green logistics. The authors grouped 18 green activities and operations into three categories - Network design, Product & Inventory, Reverse logistics. In the studies [20], the authors grouped 36 activities/practices for all activities in the supply chain such as raw material procurement, inbound logistics, transformation, outbound logistics, marketing, after-sales and appropriate product disposal.

The reviews [5,21] present a list of 58 green supply chain practices that are grouped into 16 aspects of green supply chain management (GSCM): reverse logistics, industrial symbiosis, eco-innovation practices, green information technology and systems, green design, carbon management, supplier environmental collaboration, customer environmental collaboration, ISO 14001 certification, internal management, green purchasing, green manufacturing, green packaging, green logistics, green outsourcing, green warehousing. The authors [4] analyzed the frequency of GSCM practices in the scientific papers. They identified 46 different practices. The five most frequently mentioned are green purchasing/procurement, collaboration/cooperation with customers, internal GSCM practices/environmental management, green/eco-design, investment recovery. Another [22] paper identifies the major research fields in circular supply chain management and calculates the frequency of mentioning 25 alternative solutions in scientific publications. The paper [3] points out two approaches in the existing research: green logistics practices can be considered as a composite construction for improving sustainability, or publications focus on individual practices. As an example, the authors identify 33 green logistics practices: green manufacturing, green marketing, green consumption, green reverse logistics, green transportation, green communication, information sharing, logistics emissions, green warehouse, green packaging, green vehicle technologies, alternative fuels, eco-driving, green transport management, green logistics systems, green modal shift, eco-friendly technologies, environmental standards, green administration and logistics data management, sustainable waste management, eco-friendly transportation, waste reduction, energy-efficient operations, sustainable transport, green ware housing and building, eco-design, green purchasing, reverse logistics, responsive packaging, green monitoring and evaluation, sustainable information sharing, sustainable packaging and distribution, waste management.

In another literature review [23], all articles are categorized into two groups of mitigation actions and adaptation actions and include 7 green actions to improve environmental sustainability in third-party logistics service providers. The paper [24] attempts to identify the determinants (motivations, pressures, and incentives) and modalities (practices conducting greening transportation from shippers and logistics service providers (LSPs)) standpoint. Based on a review of publications, the authors identified 14 green logistics practices and described them. According to the authors, these practices are green modal shifts, green transportation management, green logistics systems, green vehicle technologies, eco-driving, alternative fuels, environmental management systems (EMS), reverse logistics, green administration, green packaging, green warehousing, emission data, cooperation with shippers, choice of partners.

Another literature review [25] explores the relationship between GSCM pressures, practices, and performance. The authors grouped the literature on GSCM practices — eco-design, internal environmental management, waste management, green purchasing aspect, quality, and product recovery. The authors [26] studied the relationship between Green Human Resource Management practices and Green Supply Chain Management practices.

In the systematic review [13], the papers on green practices is grouped into three macro themes: the green warehouse management, the environmental impact of warehouse construction, and the energy saving in warehousing. In the paper [14], the literature on sustainable transportation is classified into 6 decisions — network design, profit sharing, inventory, distribution organization and routing. The study [12] focuses on sustainable inventory management in green supply chains. The authors considered 25 solutions to improve the sustainability of inventory management. The paper [27] considers Industry 4.0 technologies divided by GSC aspects. The authors grouped 10 green practices into 5 aspects — reverse logistic, green design, green manufacturing, carbon emissions management and green warehousing.

In several research studies, the authors do not consider green practices as activities, but as criteria against which to evaluate individual logistics processes to improve the sustainability of the supply chain. For example, when evaluating suppliers (12 practices) [28], green practices and initiatives for sustainable hotel operations (27 attributes of green practices and initiatives for sustainable hotel operations) [29]; to assess green supply chain management (13 criteria and 79 sub-criteria) [30]; to assess the feasibility of implementing Industry 4.0 technologies in sustainable supply chains (17 criteria and 59 attributes) [31].

A review of research on the use of green practices in logistics and supply chain management revealed the following problem.

Multiple views on the content of green solutions and, consequently, insufficient systematic implementation in supply chains.

Different understanding and interpretation of green practices.

Insufficient specificity of green solutions and practices (lack of description in 71% of publications).

Fragmented use of green solutions and practices in relation to elements and functions of supply chains (procurement, production, warehousing, transportation, distribution).

3. Methodology for Systematization and Ranking of Green Logistics Methods and Instruments

The proposed methodology is based on the structural-functional approach to the green supply chain formalization. This approach defined the principles of green logistics methods and instruments systematization. Multi-criteria decision-making methods are used to rank the methods and instruments. MCDM and a system of criteria for evaluating logistics flows, the achievement of which ensures the fulfillment of sustainable supply chain development goals, are applied for ranking.

3.1. Structural-Functional Approach to the Green Supply Chain Formalization

The structural-functional approach involves the identification of supply chain-based logistics functions and the identification of corresponding abstract logistics elements. The basic logistics functions are proposed to include the following main actions with logistics flows (a) acceleration and movement, (b) deceleration and accumulation, (c) quality change and processing, (d) input into the system, (e) output from the system, and (f) coordination of logistics functions. The relevant logistics elements realizing these basic functions are (a) transport, (b) cumulative, (c) processing, (d) input, (e) output, and (f) control. The basic functions of each logistics element or supply chain element are concretized by a set of so-called supporting functions, i.e. specific actions to change the parameters of logistics flows.

With the help of a combination of abstract logistic elements realizing the corresponding basic and supporting functions, it becomes possible to model any real infrastructural element of the supply chain. It becomes possible to formalize supply chains or logistics systems at any level of detail.

The structural-functional approach is fundamentally different from the generally accepted way of identifying functional areas of logistics, such as transportation, sales, production, supply and warehousing logistics. The disadvantage of the traditional functional approach is the “binding” of logistics functions and operations to infrastructural elements of logistics chains – warehouses, industrial enterprises, supply and sales departments, transportation. This makes it difficult to identify and systematize the methods and instruments of logistics flow management, since the same method or instrument can be implemented in different functional areas of logistics [32].

The model of the green supply chain (GSC) formed using the structural-functional approach is presented in Figure 2. The GSC model is a set of logistics elements linearly ordered along with the material and accompanying financial, information and work (sevice) flow. Achievement of sustainable development goals is ensured as a result of fulfillment by each GSC element of its supporting functions with the help of green logistics methods and instruments Figure 3.

3.2. Classification of Green Logistics Methods and Instruments

The study of scientific literature has allowed us to establish that different terminology is used in relation to solutions to reduce negative environmental impact in logistics. The most common terms are “green practices”, “GSCM practices”, “green factors”, “green measures”, “green activities”, “green initiatives”, “green drivers”, “solution”, etc.

We propose to use the terms “green logistics methods” and “green logistics instruments” as generalized concepts for various green solutions in the field of logistics activities. The main purpose of implementation of green logistics methods and instruments is to identify and eliminate deviations of their parameters that hinder the achievement of Sustainable Development Goals (SDGs).

In the previous paper [33], we proposed a system of green logistics methods and instruments. This system consists of 27 methods and 105 instruments. We have established what specific SDGs are achieved by the realization of each method and instrument. Subsequent studies [32,34,35,36,37,38] allowed us to clarify, adjust and extend the original system by a detailed description of each instrument.

The classification of methods and instruments presented in this study is made using the following classification features:

• Correspondence to the elements of the supply chain to avoid duplication of methods and instruments at different stages of the logistics process, as well as to identify missing and promising methods and instruments.
• Correspondence to supporting functions of supply chain elements. Traditionally, logistics functional areas are focused on cost reduction and quality improvement. Specialization of green logistics methods and instruments by supporting functions is necessary to achieve social and environmental goals additionally.
• Correspondence of instruments to the green logistics methods, i.e., realization of a certain method by a set of instruments.

In addition, the proposed classification is based on the following principles:

• Consideration of green logistics methods and instruments as a unified system for achieving SDGs. The object of management is logistics flows in the supply chain.
• Using the best green practices, eco-programs and projects with the participation of political, social and economic institutions, scientific organizations, international unions and organizations to form and improve the system of green logistics methods and instruments.

Thus, we propose the following concepts:

• Green Logistics Method (GLM) – a set of solutions to achieve the SDGs by realizing the basic and supporting logistics functions of a certain element of the logistics system or supply chain.
• Green Logistics Instruments (GLI) – a specific solution for changing the parameters of logistics flows to implement the corresponding green logistics method.

3.3. Multi-Criteria Ranking of Green Logistics Methods and Instruments

A GLM and GLI system can consist of multiple methods and instruments specialized by logistics elements and functions. Different elements of the supply chain may have different objectives in changing the parameters of logistics flows by GLM and GLI. Therefore, ranking and selection of GLM and GLI is proposed to be done using multi-criteria decision-making (MCDM) techniques.

The methodology for multi-criteria assessment and ranking of GLMs and GLIs consists of the following steps:

Step 1. Design a list of methods and instruments based on the results of analyzing scientific papers in the field of green solutions and practices as applied to supply chains.

Step 2. Formation of GLM and GLI system with observance of classification attributes and principles presented in Section 3.2. Grouping GLM by supporting functions of logistics elements. Grouping of GLIs by GLM compliance.

Step 3. Selection of criteria system and formation of a set of multi-criteria models for GLM and GLI ranking.

We propose to use estimates of logistic flow parameters (Figure 4) as a system of criteria. This choice is based on the ultimate influence of instruments on these parameters, as a result of which the achievement of the SDGs is ensured. A detailed description of the selected two-level criteria system is presented in [32,39]. The set of multi-criteria models includes one GLM ranking model for the entire supply chain and six GLI ranking models, one for each logistics element.

Step 4. Formation of an expert group, preparation of questionnaires for GLM and GLI assessment using a system of criteria. The expert group should include representatives of the academic community, as well as businesses in the field of logistics and supply chain management. It is desirable that the experts' qualifications allow them to adequately assess the importance of methods and instrumentss for different elements of the supply chain.

Step 5. Calculation of weights of criteria for evaluation of green logistics methods and instruments. Since impacts on different parameters of logistics flows using GLM and GLI have different impacts on the achievement of SDGs, it is necessary to calculate the weights of criteria for assessing logistics flows. The most common methods for calculating criteria weights in green supply chains are AHP, ANP, BWM, CRITIC, DEMATEL, FUCOM and others [38]. The input data for calculations using these methods are expert estimates of criteria weights. Multiple scales can be used to improve the accuracy of the estimation, for example with fuzzy, rough and gray numbers.

Step 6. Obtaining expert evaluations of alternatives. Assessment can be done using a variety of scales. Formation of initial decision-making matrices for ranking methods (1) and instruments (2) considering the criteria weights. The initial matrices in general form have the following.

$$X_{met}=\begin{array}{c}\begin{array}{l} \\ \end{array}\\ \begin{array}{c}{M}_1\\ M_2\\ ⋮\\ M_m\end{array}\end{array}\begin{array}{c}\begin{array}{cccc}\begin{array}{l}{С}_1\\ w_1\end{array}& \begin{array}{l}{С}_2\\ w_2\end{array}& \begin{array}{l}\cdots \\ \dots \end{array}& \begin{array}{l}{С}_n\\ w_n\end{array}\end{array}\\ \left(\begin{array}{cccc}{x}_{11}& x_{12}& \cdots & x_{1n}\\ x_{21}& x_{22}& \cdots & x_{1n}\\ ⋮& ⋮& ⋮& ⋮\\ x_{m1}& x_{m2}& \cdots & x_{mn}\end{array}\right)\end{array}$$

(1)

$$X_{inst}=\begin{array}{c}\begin{array}{l} \\ \end{array}\\ \begin{array}{c}{I}_1\\ I_2\\ ⋮\\ I_k\end{array}\end{array}\begin{array}{c}\begin{array}{cccc}\begin{array}{l}{С}_1\\ w_1\end{array}& \begin{array}{l}{С}_2\\ w_2\end{array}& \begin{array}{l}\cdots \\ \dots \end{array}& \begin{array}{l}{С}_n\\ w_n\end{array}\end{array}\\ \left(\begin{array}{cccc}{x}_{11}& x_{12}& \cdots & x_{1n}\\ x_{21}& x_{22}& \cdots & x_{1n}\\ ⋮& ⋮& ⋮& ⋮\\ x_{k1}& x_{k2}& \cdots & x_{kn}\end{array}\right)\end{array}$$

(2)

where M = {M₁, M₂ …M_m} – green logistics methods; m – number of methods; I = {I₁, I₂ …I_k} – green logistics instruments; k – number of instruments; C = {C₁, C₂ …C_n} – criteria of logistics flows; n – number of criteria; w = {w₁, w₂ …w_n} – weight of criteria; x_ij or x_gj – respectively the evaluation value of i – method and g – instruments according to j – criterion C.

Step 7. Multi-criteria ranking of green logistics methods and instruments using MCDM. The selection of a specific MCDM is necessary in this step. MCDMs differ in their data aggregation methods and algorithms, accuracy of results, and computational labor intensity. Common methods for ranking green supply chain solutions are SAW, TOPSIS, PROMETHEE, COPRAS, ARAS, WASPAS, EDAS, MABAC, CODAS, MARCOS, etc. [37].

Step 8: Sensitivity analysis of the ranking results. The results obtained using one of the selected MCDMs are compared with those calculated by other multi-criteria methods. The ranked GLMs and GLIs are used by decision makers to align sustainability programs and projects across all elements of the supply chain.

The multi-criteria assessment framework for GLM and GLI is presented in Figure 5. The criteria system (Figure 4) is shown as an example on this framework.

4. Case Study

This section presents an example of ranking green logistics methods and instruments. In the first step, we analyzed 184 research papers on the use of various green solutions and practices in supply chains. The identified green solutions and practices are grouped according to the supporting functions of green supply chain elements. The results of the research analysis are presented in Table 2.

Figure 6, Figure 7, Figure 8, Figure 9, Figure 10 and Figure 11 shows the results of systematization of green logistics methods and instruments separately for each logistic element. The corresponding elements are highlighted in color. A detailed description of each green logistics instrument is given in Table 3, Table 4, Table 5, Table 6, Table 7 and Table 8. The names of the instruments are close to the formulations of traditional logistics support functions and tasks. However, from the perspective of green logistics, they should be considered as methods and instruments for achieving sustainable development goals. These goals are indicated in the figures by the corresponding well-known pictograms [204].

Seven MCDM models are formed to rank green logistics methods and instruments.

1. Supply chain model (27 methods — M1.1-M6.5).

2. Control element model (21 instruments — I1.1.1-I1.5.4).

3. Input element model (14 instruments — I2.1.1-I2.4.5).

4. Processing element model (17 instruments — I3.1.1-I3.5.4).

5. Cumulative element model (17 instruments — I4.1.1-I4.4.4).

6. Transport element model (18 instruments — I5.1.1-I5.4.4).

7. Output element model (18 instruments — I6.1.1-I6.5.4).

A system of 15 logistics flow criteria is used to evaluate green logistics methods and instruments. The weight values of the criteria of logistic flows are taken from [205]. Fuzzy Analytic Hierarchy Process (Fuzzy AHP) is used to evaluate the weight of criteria.

A group of five academic experts in the field of Supply chain management, transport systems, Logistics was formed to perform the assessment. The average length of service of the experts is 25.4 years. The experts evaluated the impact of green logistics methods and instruments on logistics flow criteria on a five-point scale: 1 – very low, 2 — low, 3 — medium, 4 — high, 5 — very high. The results of expert assessments are presented in Table 10.

For ranking green logistics methods and instruments, we used MCDM methods Technique for Order Preference by Similarity area Comparison Ideal Solution (TOPSIS), Multi-Attributive Border Approximation Area Comparison (MABAC) and Measurement of Alternatives and Ranking according to Compromise Solution (MARCOS). These methods are widely used for multi-criteria evaluation of various aspects of sustainable and green supply chains. The main steps of each method can be found in [206,207,208].

Table 11, Table 12, Table 13, Table 14, Table 15, Table 16 and Table 17 and Figure 12, Figure 13, Figure 14, Figure 15, Figure 16, Figure 17 and Figure 18 present the ranking results. Sensitivity assessment of the ranking results was performed based on the calculation of Spearman rank correlation coefficient. The average correlation coefficient was for MCDM model of green logistics methods – 0.984. For MCDM model of green logistics instruments: Control element – 0.982; Input element – 0.947; Processing element – 0.979; Cumulative element – 0.983; Transport element – 0.974; Output element – 0.980. The values of the coefficients show a high correlation, which indicates the reliability of the results obtained.

Additionally, we calculated the value of the Mean Relative Error of the Ranking results (MRER) for each MCDM model using the following formula/

$$MRER={\displaystyle \frac{{\displaystyle \sum _{i=1}^M{\displaystyle \sum _{l=1}^{L-1}\left(\left|R_{il}-R_{il+1}\right|+\left|R_{iL}-R_{i1}\right|\right)}}}{M\times L}},$$

where R_il – rank of the i-th alternative (GLM or GLI), calculated by the l-th method, M – number of alternatives, L – number of ranking methods, L ≥ 3.

The MRER values for GLM were 1.135. The MRER values for GLI: Control element — 1.015; Input element — 0.904; Processing element — 0.901; Cumulative element — 0.745; Transport element — 0.814; Output element — 0.851. The calculated MRER values show the minimum deviation in the ranks obtained in the evaluation by different methods.

The two most significant green logistics methods are M2.4 Procurement planning, implementation and control (rank #1), M5.3 Transportation management and transportation planning (rank #2). Rank #3 is assigned to two green logistics methods — M1.4 Design and implementation of intelligent transportation system (MABAC, MARCOS assessment) and M3.4 Process flow management (TOPSIS assessment). The three least significant green logistics methods are M4.1 Environmental design of warehouse complexes (rank #27), M4.2 Use of environmentally acceptable handling equipment and vehicles (rank #26). Rank #25 is assigned to three green logistics methods — M1.1 Environmental management (TOPSIS score), M3.5 Human resource management (MARCOS score) and M5.2 Selection of environmentally friendly vehicles (MABAC score).

Ranking the green logistics instruments separately by supply chain elements allowed us to establish the most important instruments (Rank #1): I1.5.2 Electronic data interchange (Control Element), I2.4.1 Minimization of procurement volume (Input Element), I3.4.1 Optimization of process flow parameters (Processing Element), I4.4.4 Unification of batch shipment (Cumulative Element), I5.2.1 Vehicles with the least environmental impact (Transportation Element), I6.3.1 Selection of green distribution channels (Output Element).

Green logistics instruments with the lowest rank: I1.4.1. Data Mining techniques and I1.4.3. Situational management techniques (Control Element), I2.2.1. Selection of environmentally friendly raw materials (Input element), I3.4.3. Production according to eco design requirements (Processing element), I4.4.2. Operational control of inventory management system parameters (Cumulative Element), I5.3.6. Reduction of return empty mileage (Transport Element), I6.1.3. Analysis of the distribution system in terms of environmental impact, and I6.3.4. Location of distribution centers with minimal environmental impact (Output Element).

5. Conclusions

The methodology of classification and ranking of methods and instruments of green logistics in supply chains is presented. The peculiarity of the proposed approach is the consideration of the supply chain as a universal model of six elements (Control, Input, Processing, Cumulative, Transport, and Output) each of which implements all known functional areas of logistics for the promotion and processing of material flow. Each element performs a set of supporting functions peculiar only to it. To improve the sustainability of the supply chain, the performance of supporting functions by elements should be based on the implementation of methods and instruments of green logistics.

Based on the literature review, the classification of currently existing green solutions and practices by supporting functions of supply chain elements is performed. A universal system of green logistics methods and instruments is proposed, and definitions of each instrument are given. This system includes 27 methods and 105 instruments.

The system of criteria for assessing logistics flows is used as criteria for the effectiveness of the implementation of green logistics methods and instruments. The implementation of green logistics instruments has an impact on the criteria of logistics flows and allows achieving the goals of sustainable development of supply chains. To assess the impact of green logistics methods and instruments on the criteria of logistics flows, it is proposed to use multi-criteria decision-making methods.

Ranking green logistics methods and instruments using MCDM methods was performed. Fuzzy AHP was used to estimate the weight of criteria of logistic flows. TOPSIS, MABAC and MARCOS methods were used to rank the methods and instruments. The ranking results by different MCDM showed high convergence — The average Spearman rank correlation coefficient was 0.975, the value of the Mean Relative Error of the Ranking results was 0.909.

The most significant methods of green logistics are “Procurement planning, execution and supply controlling”, “Transport management and transport planning” “Development and implementation of intelligent transport system” and “Technological flows management”. The most significant instruments of green logistics in the supply chain elements are: “Electronic Data Interchange” (Control element), “Minimization of purchasing volume” (Input element), “Optimization of technological flows’ parameters” (Processing element), “Unitization of party shipment” (Cumulative element), “Vehicles with the least impact on the environment” (Transport element), “Selection of environmentally friendly distribution channels” (Output element).

Thus, we proposed considering the developed system of green logistics methods and instruments as a universal framework for the implementation of management decisions to improve supply chain sustainability. The limitation of this study is the small number of experts involved in the evaluation of the ranking of methods and instruments, which does not allow the results to be interpreted for global supply chains. An important direction for future research is to evaluate and rank methods and instruments, considering the constraints on available resources for effective implementation of GLM and GLI in supply chains.