Introduction

Conceptually, procurement represents a “multipart process, which includes vendor certification and selection, requisition preparation and approval, order placement, goods receipt, reconciliation and payment of the invoice, and order archiving” [108]. Procurement is a critical organisational function that aims to ensure the quality of purchased materials (or services) and connects supplier capabilities to in-house manufacturing and distribution operations [34]. The procurement function is driven by three distinct criteria: cost, quality, and delivery [42]. Apart from these more conventional requirements, procurement concerns the environmental consequences of supply chain operations and management decisions [79, 113, 124, 132]. Numerous organisations now prioritise environmental stewardship as a business priority, recognising that environmental initiatives have the potential to ensure businesses’ survival and competitive advantage [51]. As a result of the significance of these environmental objectives, interest in green procurement has increased. By adopting this practice [4], businesses can reduce waste and promote recycling and reclamation of purchased materials without impairing performance [81]. Additionally, green procurement can help organisations reduce energy consumption, increase operational efficiencies, and optimise their financial performance [68, 111, 129]. Incorporating environmental standards into procurement processes also requires buyers to consider the environmental impacts of the products and services they procure and conduct an environmental assessment before purchasing [4].

Given the increased focus on environmental sustainability [141], procurement managers are constantly attempting to minimise the environmental impacts of products by selecting those that cause the least damage to the ecology. Additionally, they are motivated to develop strategies for resource conservation [92]. Moreover, as businesses continue to shift toward sustainable environmental operations throughout their organisations and supply chain networks, the supply chain function’s traditional role is being reconsidered [45]. Businesses can now source more sustainable and environmentally friendly materials with the fewest possible adverse environmental and human health effects [2, 21]. Additionally, green procurement is critical for any organisation seeking to improve its environmental performance. In this regard, Carter et al. [22] emphasised that establishing environmental programs and initiatives can increase social sustainability by enabling procurement managers to create value and, importantly, influence the environmental behaviours of businesses and their supply chain partners. Nonetheless, implementing green procurement practices remains challenging due to inadequate tools, knowledge, and training on operationalising green procurement methods [5, 6]. Collaboration with supply chain partners in the external environment is another significant barrier for organisations engaged in green procurement practices, as stakeholders may hold divergent perspectives on what constitutes green procurement.

It is essential to thoroughly evaluate the academic literature on green procurement because of the importance of this topic and the rapid rise in research. There have been a few attempts to synthesise green procurement research. To illustrate, Appolloni et al. [7] systematically reviewed papers published between 1996 and 2013 and proposed future research directions. The review found that most of the literature focused on three key themes: the motivations and drivers for adopting green procurement, the challenges for its adoption, and the impact of green procurement on performance. Similarly, Cheng et al. [23] recently reviewed the literature on green public procurement and analysed articles from 2000 to 2016. The authors discovered that research had been centred on the particular effect of green public procurement adoption and overlooked the efficiency and innovation of environmental policy tools. Beer and Lemmer [14] critically analysed the practices related to supply chain management and green procurement to reduce pollution and greenhouse gas emissions. Finally, Vejaratnam et al. [125] systematically reviewed 29 studies to ascertain the barriers to implementing green government procurement. The results indicate that the primary barrier to green government procurement adoption is a lack of knowledge and awareness, while financial constraints were unimportant. While these reviews provided valuable insights into the green procurement literature, this research stream has not yet been studied utilising the main path analysis (MPA) approach to investigate the knowledge dissemination paths. The MPA has been extensively employed in a range of disciplines, including the Internet of Things [106], restaurant research [97], blockchain technology [136], circular economy [104], and environmental innovation [12].

To close this knowledge gap, this paper will explore the evolution of knowledge in green procurement using main path analysis (MPA) and keyword co-occurrence network. Combining these two techniques enables the identification of hot topics and critical points that have played a significant role in the historical development of green procurement. Analysing various main paths enables an intuitive representation of the knowledge diffusion trajectories and structure in green procurement. Additionally, quantitative approaches can help scholars reduce bias and efficiently collect and effectively evaluate a larger sample of publications. These approaches can aid researchers in better understanding the field’s historical development, comprehending its current state, and identifying future research opportunities.

This review makes several contributions to the literature on green procurement. First, the application of keyword co-occurrence clustering and MPA aims to comprehensively examine the green procurement field, which has been overlooked in the prior literature. Second, this study takes a novel approach by examining the knowledge diffusion paths in green procurement from different standpoints, including local (forward and backward), global, and key-route main paths. As a result, the progress of green procurement knowledge and its converging–diverging cycles can be vividly visualised and explained.

The following is the breakdown of the review. Data collection and methods are discussed in the “Research Design” section. The results of the keyword co-occurrence network are discussed in the “Keyword Co-occurrence Network Analysis” section before moving on to MPA in the “MPA Results” section. The discussion in the “Discussion” section is detailed, and the work is summarised in the “Conclusion” section.

Research Design

Article Collection

Data quality is a prerequisite for generating interpretable and meaningful results. The Scopus database constitutes one of the most dependable and trustworthy sources, as it contains numerous authoritative journals [27, 86, 87]. Additionally, researchers rely on Scopus because it allows the application of bibliometric analyses across various research domains [33, 38, 122]. As a result, Scopus is this paper’s primary data aggregation platform. The review’s detailed research process is depicted in Fig. 1. Based on the guidance provided by Appolloni et al. [7], the search query used in the current study is composed as follows: TITLE-ABS-KEY (“Green Procurement” OR “Green Purchas*” OR “Sustainable Procurement” OR “Sustainable Purchas*” OR “Ethical Procurement” OR “Environmental Procurement”), where TITLE and ABS and KEY denote the title, abstract, and keywords fields, respectively. The selection of these specific keywords and their combinations was driven by the necessity to encompass the broad and diverse landscape of the green procurement literature. These terms were chosen because they effectively capture the various terminologies used to describe procurement processes to promote environmental sustainability. The use of the asterisk (*) in “Green Purchas*” and “Sustainable Purchas*” was to ensure that all variants of the word, such as purchase and purchasing, were included in the search, thereby enhancing the comprehensiveness of the search process. “Green Procurement” and “Sustainable Procurement” reflect practices incorporating environmental considerations into procurement decision-making. “Ethical Procurement” and “Environmental Procurement” are included to encapsulate procurement practices that integrate broader ethical and environmental concerns. This careful selection and combination of keywords ensured that the search query was broad enough to capture all relevant literature in the field while specific enough to exclude unrelated studies. In this manner, we enhanced methodological clarity and ensured a comprehensive review of the existing literature. The period encompasses all publications before 2022, and the papers were gathered on May 29, 2022. Only English-speaking journal publications were considered for the review. In total, 452 documents from the Scopus platform were identified and downloaded. The present study also utilised the Pajek software for the MPA of green procurement research. Pajek is a versatile software program widely used in network analysis, including social network analysis, network visualisation, and network data manipulation [35]. The software is particularly valuable for analysing large networks, which involves exploring relationships among various publications in the green procurement literature. Using Pajek, we constructed and visualised a comprehensive citation network based on the collected data, thus providing a robust framework for identifying and analysing the primary subjects and evolution within the area of green procurement. The robust analytical capabilities of Pajek were essential in revealing significant citation linkages between publications and identifying key topical themes and influential articles in the field [137]. This, in turn, enhanced our understanding of the information dissemination processes in the green procurement research field.

Fig. 1
figure 1

Research process

Full size image

Methodology

We created a network of phrase co-occurrences to understand green procurement research better. Like co-citation networks, keyword co-occurrence networks map out the links between keywords that appear in the same articles [54, 105]. One way to find active research frontiers in any area of expertise is to analyse a keyword co-occurrence network, as Su and Lee [115] point out. If two terms in the network are regularly found together in the same articles, they are likely to be related. In this paper, we utilise a co-occurrence network analysis of keywords to explain the present conceptual structure of green procurement research and to analyse the most important themes emerging from the keywords. VOSviewer was chosen as the network-generation software due to its compatibility with the BibExcel computer programme [38]. In the keyword co-occurrence network, the size of each node represents the frequency with which that keyword appears in articles, while the breadth of the edges represents the frequency with which any given combination of keywords appears in articles [102]. The most important topics addressed in green procurement studies can be identified by grouping related terms.

Several citation-based analytic approaches were applied in addition to the keyword co-occurrence network analysis, including the main path analysis (MPA). One of the many uses of MPA is to track the evolution of a field’s body of knowledge. These procedures would allow researchers to understand the historical development of a field of study, the dominant theoretical frameworks applied, and the potential future areas of inquiry within an academic domain [120]. The MPA was chosen over other methods for several reasons. Firstly, MPA helps unravel the research landscape’s complexity by identifying the most influential paths through the citation network, which might not be immediately evident through a simple literature review [100]. Secondly, compared to other similar methods, MPA provides an objective, quantitatively rigorous, and replicable approach to tracing the knowledge diffusion process over time, which is an advantage when dealing with large datasets [99, 135], like the one in this study. The method’s systematic nature helps to eliminate any potential bias, thus providing a more accurate representation of the knowledge structure in green procurement [134]. Furthermore, since Hummon and Dereian [53] proposed MPA, it has gained widespread use and is used by many researchers to uncover the most influential studies in various disciplines [70]. Publications on MPA may be roughly divided into two categories: those developing the MPA and those applying it in various settings [69]. Reviews on topics like resource-based theory, data quality, corporate social responsibility, the Internet of Things, social commerce, sustainable technology innovation, halal food, and blockchain technology have all made use of MPA [35, 74, 75, 103, 116, 121, 130, 139]. Such broad application further validates the versatility and usefulness of MPA as a method of analysis in various settings.

A citation network was created to demonstrate how MPA works (see Fig. 2). Consider two publications that each mentions the other. Nodes (like A, B, and C) in a network and “links” connect other nodes (e.g., A-C, A-D). Nodes referenced in other articles are sources but do not cite other works (e.g., A and B). On the other hand, sinks do not have any citations and instead link to other articles (e.g., H and I).

Fig. 2
figure 2

An exemplary citation network weighted with SPC values

Full size image

Main path analysis relies heavily on traversal weight, an example of the many approaches needed to generate unique connection values. Node pair projection count (NPPC), search path node pair (SPNP), and search path link count (SPLC) are all of these [53]. The authors of this research used search path count (SPC) [13], which is the number of times a link is crossed if all potential citation chains are run through from all sources to all sinks in a citation network. Using E-J as an example, the link’s SPC value is 2 since it is traversed by two paths, A-E-J and B-E-J.

The weighted network was constructed by calculating SPCs. Our next step is to map out the main paths. Green procurement literature was examined using local (forward + backward), global, and key-route main paths. These four paths are complementary and cannot be swapped [136]. In the same way that the local main path analysis can find critical linkages, the global main path analysis can determine the path with the greatest SPC. In contrast to these approaches, the key-route main path can disclose the divergence and convergence of knowledge in a particular study subject [70].

Our main approach commences with a comparison of links between sources. Following this, we determine which link(s) possess the highest search path count (SPC) value and designate these nodes as new starting points. To reach a sink node, this process is reiterated. The resulting path is termed the forward local main path. Our analysis identifies the forward local main path as A-D, B-D, D-C, D-G, C-F, G-I, G-H, G-J, F-I, F–H, and F-J.

Contrastingly, the backward local main path operates reversely, moving from sinks to sources. The forward local main path signifies the papers with the most extensive followership, while the backward local main path represents works that borrow extensively from preceding research [69]. Our analysis defines the backward local main path as A-D, B-D, A-E, B-E, D-G, E–G, G-I, G-H, and G-J.

However, the aforementioned local main paths may not exhibit the highest SPC value. As a result, we must generate the global main path. In our study, the global main path is identified as A-D, B-D, D-C, C-F, F-I, F–H, and F-J because it encompasses the most comprehensive network of connections, effectively representing the overarching structure of the network under study.

None of the previously mentioned paths can extract the links with the highest SPCs. To address this, we analyse the main key-route path, beginning with the links with the highest SPCs. This path continues forward until it reaches a sink and then traces back until it finds a source [69]. According to our exemplary citation network, the key-route main paths are all arcs except A-C and E-J. The number two corresponds to the selection of the two highest SCPs (9 and 6). Selecting more key-routes allows for the acquisition of more detailed information.

In this study, each of the main path analyses deployed offers distinctive insights into the green procurement research landscape and underlines the evolution of the field and the significant studies that contributed to this evolution. For instance, local main paths (both forward and backward) were employed to discern the direct scholarly influence of specific green procurement research publications. The forward local main path revealed which subsequent studies in green procurement were directly shaped by an initial piece of research, while the backward local main path showed which earlier studies directly fed into that seminal research work. The global main path analysis, on the other hand, provided a more holistic view of the green procurement field. It allowed researchers to identify the most influential chain of studies that essentially forms the backbone of the green procurement literature, marking its key developments from the field’s emergence to its current state. Lastly, the key-route main path analysis was implemented to overcome a specific limitation of the prior paths, which may overlook that research works with the highest citation links. By starting from the most heavily cited studies in green procurement and tracing their influence in both directions, the key-route main path unearthed the most substantial channels of academic influence within the green procurement field. Utilising all four types of main path analysis has enhanced the breadth and depth of understanding of the green procurement research landscape. This multi-pronged approach facilitated a comprehensive examination of the field and enabled the capture of direct influences of specific research, the broader evolutions within the green procurement literature, and the most impactful scholarly contributions that have shaped its trajectory.

Keyword Co-occurrence Network Analysis

Green procurement has a plethora of sub-fields that may be studied using a keyword co-occurrence network analysis. With this strategy, we can select the most important areas of exploration in this field of study. To begin, we retrieved, reviewed, and refined all of the author-supplied keywords that would serve as our analysis unit. For instance, we started using abbreviations for the original, longer terms (e.g., green supply chain management (GSCM)). We used VOSviewer to import the data and build the network. Next, we employed density-based spatial clustering using the full counting approach [62] and setting the threshold of 4 keyword occurrences.

This led to forming a network of five clusters (see Fig. 3). Each node in the network represents a separate keyword, and the colour of its corresponding node indicates the cluster to which it belongs. The frequency with which the keyword occurs is directly proportional to the network node size. Finally, the density is represented by the inter-node distance. This indicates that when a network is dense, its nodes will be closer together. Table 1 displays the most common ten terms from each cluster.

Fig. 3
figure 3

Keyword co-occurrence network

Full size image
Table 1 Top 10 most frequent keywords
Full size table

From the figure, the most important cluster is the red one. This cluster revolves around green supply chain management (GSCM). GSCM represents a philosophy that seeks to improve the environmental performance of firms [11]. Under the constant pressure from supply chain stakeholders and environmental regulations, firms must enhance their environmental performance by engaging in green procurement, manufacturing, product recycling, and eco-design development. According to Liu et al. [71], GSCM aims to incorporate the green concept into every link of supply chain management and assess the environmental effect of every link. The impact of GSCM practices (e.g., green procurement, eco-design, green manufacturing, internal environmental management) on environmental sustainability has been investigated by several scholars through the application of structural equation modelling (SEM) [24, 46, 82, 110]. Furthermore, scholars have extensively studied this topic in Malaysia [41, 66, 84].

Furthermore, the second cluster focuses on sustainable public procurement. The most frequent keywords include “sustainable procurement”, “GPP” (green public procurement), “sustainable development”, “PP” (public procurement), and “SPP” (sustainable public procurement). Public procurement is recognised among academics, practitioners, and policymakers as a crucial tool supporting government operations [88, 101]. The relevance of public procurement manifests in the willingness of governments to set regulations that entice public agencies to establish sustainable public procurement. In addition, sustainable public procurement assumes a strategic role in fulfilling specific governmental goals such as economic growth, social sustainability, and innovation [126]. Sustainable public procurement is based on several reformation initiatives that promote transparency and accountability [64]. For example, governments can achieve sustainable procurement by controlling their spending power, impacting multiple sectors, including the private sector [9]. The third place for sustainable development suggests that green procurement might help achieve sustainable development and the overarching goal of the green procurement field [78]. As a transition from conventional to circular procurement [125], green procurement is an environmental approach that aids sustainable development by providing environmentally friendly goods and services [127]. Green procurement was initiated in the 1980s and 1990s. It inspires businesses to provide eco-friendly goods and services and lays the groundwork for long-term growth. Customers’ heightened awareness of environmental challenges and the need for long-term planning motivate them to adopt green buying practices.

“Sustainability” is the most frequent keyword used in the third cluster. The cluster’s other relevant keywords are “procurement” and “SCM” (supply chain management), “AHP” (analytical hierarchical process”, and “LCA” (life cycle assessment). Embedding sustainability principles in procurement can positively influence outsourcing decisions, increase resource use efficiency, and reduce the impact of procurement projects on the economy, environment, and society [31]. Similarly, the commitment to sustainable procurement can contribute to the green economy and sustainability goals by aligning consumption and production trends and boosting the market for environmentally friendly and sustainable products and services [26]. Several studies in this cluster applied AHP and LCA to support sustainable modelling and decision-making. For example, Ozelkan and Stephens [90] use AHP and LCA to resolve a sustainable purchasing problem from a major internet service provider (ISP) in the telecommunications sector, where the objective is to choose the best jacketing option for fibre optic cabling. Ahsan and Rahman [3] employ AHP to examine the issues of adopting green public procurement in the Australian public healthcare sector. According to the results of their investigation, the primary challenges in green procurement include government, non-governmental organisations (NGOs) and public issues, and organisational difficulties. Pullman and Wikoff [95] leverage stakeholder and LCA theories to understand the environmental effects of stakeholder-driven sustainable purchasing strategies in institutional settings. Finally, Butt et al. [19] argue that for LCA to be relevant for decision support in a procurement scenario, it is essential to have a thorough understanding of the technical characteristics or attributes that comprise the life cycle phases.

The fourth cluster in yellow revolves around green supplier selection. Keywords such as “supplier selection”, “green supplier selection”, “CO2 emission”, and “CSR” (corporate social responsibility) are therefore included in this cluster. In the competitive business environment, there has been continuous growth in outsourcing materials, parts, services, and components to suppliers. As a result, within new procurement and manufacturing strategies, the crucial importance of suppliers has been emphasised for achieving competitive advantage and increasing firm performance [10, 55]. Consequently, supplier selection has evolved into a strategic decision in supply chain management (SCM) [91, 96, 107]. According to Yu et al. [138], supplier selection is critical in establishing a green supply chain and developing strong collaboration with suppliers. As a critical element of green SCM, green supplier selection represents a multi-criteria decision-making (MCDM) problem that includes several quantitative and qualitative factors [72]. For example, Awasthi et al. [8] evaluate the environmental performance of suppliers using fuzzy TOPSIS. Kuo et al. [63] combine data envelopment analysis (DEA), an artificial neural network (ANN), and an analytical network process (ANP) for the selection of green suppliers. In addition, Büyüközkan and Çifçi [20] suggest a hybrid fuzzy MCDM model for green supplier assessment that integrates the Decision-Making Trial and Evaluation Laboratory (DEMATEL), ANP, and TOPSIS in an uncertain environment. The high frequency of CSR reflects its importance when implementing sustainable procurement activities, supplier selection, and order allocation [40]. CSR can be included alongside environmental protection, pollution control, green innovation, eco-design, and hazardous substance management as a criterion in green supplier selection [37]. This also would help ensure that the suppliers act socially responsibly regarding the environment and labour practices [112]. Overall, this cluster analysis shows that the predominant method to examine supplier selection in green procurement is quantitative, using various MCDM techniques.

Finally, the last cluster in purple deals with environmental management in developing countries. As a growing trend, environmental management constitutes a series of initiatives designed to reduce the environmental effect of a firm’s operations on the environment [46, 112]. Firms can minimise environmental impact by developing products, processes, and procedures that optimise energy consumption, reduce waste, promote environmentally friendly and sustainable resources, and employ environmental management systems [56]. Because of the diversity and complexity of environmental management practices and the various attitudes with which firms address environmental issues [119], many business leaders and academics have been characterising firms based on their environmental activities. In the context of developing countries, mainly Malaysia and Brazil, several studies have been carried out to examine environmental issues and the role of green supply chain practices, including green purchasing activities, in supporting sustainable business operations and manufacturing [28,29,30, 49, 56]. The high frequency of keywords “PLS” (partial least squares) and “RBV” (resource-based view) indicates that scholars mainly conduct empirical studies to investigate environmental management and green supply chain practices in developing countries drawing on the RBV theory to hypothesise and develop strong conceptual models.

MPA Results

Local (forward and backward) main path analysis, global main path analysis, and key-route main path analysis were performed. These approaches are complementary and aid in identifying the most crucial information dissemination routes in the area of green procurement. Each node in the figures represents each article, along with the lead author’s name and publishing year. The directed linkages represent the flow of information, and the thickness of the links signifies their importance or a greater SPC value.

The Citation Network

Figure 4 is a visual representation of the citation network in our study. It comprises 452 nodes, representing individual research papers, and 1859 edges, symbolising the citation relationships between these papers. The largest and most prominent feature in the diagram is the central subnetwork. This contains 390 tightly interlinked nodes, which signifies many research papers that share many citation relationships. This core subnetwork is the heart of our study for MPA. Its dense interconnections imply a high degree of consensus or shared knowledge in this area of research. The largest subnetwork shows that many of these publications cite each other, thereby informing and building upon each other’s work. The second type of node is located near the periphery of the network. These nodes have fewer citations, implying that they are less frequently referenced by other papers in the network. However, they are still connected to many articles, bridging the core subnetwork and the wider body of knowledge in this field. They may represent more specialised or niche research areas that, while not as extensively cited, still contribute valuable insights to the field. Lastly, the remaining nodes are scattered throughout the network, seemingly isolated and disconnected from the main body of articles. These represent papers that do not have strong citation connections to other works in the network. This could suggest that they represent emerging research areas, novel theories, or unorthodox viewpoints that have not yet been widely adopted or recognised by the rest of the field. Through Fig. 8, we visualise the structure and interconnectedness of research in the green procurement field, providing a bird’s eye view of the citation landscape, key papers, and research trends.

Fig. 4
figure 4

Citation network of the sample

Full size image

Local Main Path Analysis

The local main paths, shown in Figs. 5 and 6, depict the local main paths, consisting of 15 and 18 articles, respectively. Three common articles in both paths and distinct nodes are coloured yellow.

Fig. 5
figure 5

The forward local main path

Full size image
Fig. 6
figure 6

The backward local main path

Full size image

As shown in Fig. 5, Marron [76] is the first publication on the forward local main path that leads to the beginning of research into environmentally friendly purchasing practices. In this article, the author examines the outcomes of green government procurement policies and notes that if marginal product costs rise, private market reactions counteract changes in government procurement. Faith-Ell et al. [32] present the results of two studies on implementing environmental requirements in Swedish road maintenance contracts and conclude that environmental requirements must be made clearer and simple to make green procurement successful, and reasonable follow-up procedures are necessary. Based on Faith-Ell et al. [32], Geng and Doberstein [39] explore the application of green government procurement in China and argue that greening government procurement in the country has become one of the numerous policy tools to enhance the environmental performance of goods and services. However, the authors report that the lack of guidelines and the limited environmental awareness are barriers to promoting green government procurement in developing countries. Research has become diverse after these three papers, with many articles appearing on the two local main paths. In the forward local main path, Michelsen and de Boer [79] examine the role of municipalities and local governments in green public procurement using survey data collected in Norway.

The findings reveal that green procurement is substantially more prevalent in large municipalities than in small ones and that there is a need for better environmental awareness among counties and municipalities and more direction from the national authorities. Testa et al. [117] attempt to evaluate the determinants and challenges of green procurement adoption in the public sector in Italy. The results of their econometric analysis demonstrate that the dimension of public authorities and the existing awareness of tools for facilitating government public procurement have a favourable and significant impact on the likelihood that they embrace green public procurement practices. In Zhu et al. [140], a conceptual model that hypothesises the moderating impacts of green public procurement knowledge on the linkages between green public procurement drivers and practices is developed to understand the adoption issues of green public procurement in China. Based on data obtained from 193 Chinese government officials, the authors discover that rewards and incentive gains, regulations, and stakeholders play a role in encouraging the implementation of green public procurement practices. Several organisational factors have been identified as drivers or barriers to implementing sustainable public procurement. However, the ways these factors impact the implementation and the level of sustainable public procurement remain unclear. To bridge this gap, Grandia [43] examines whether behaviour is a mediator between knowledge, commitment to change, and implementing sustainable procurement in Dutch national government procurement initiatives. The findings indicate that sustainable procurement behaviour positively mediates the link between affective commitment to change and knowledge and the relationship between compulsory and voluntary sustainable procurement. As a result, public organisations should concentrate on expanding their awareness of sustainability and the environment and increasing affective commitment to change and sustainable buying practices to facilitate the implementation of sustainable public procurement. The following paper, by Keulemans and Van de Walle [59], seeks to investigate and describe public preferences for various public procurement procedures. Using public opinion data on 26,836 citizens from 27 European nations, EU citizens expect public authorities to assess several aspects of every procurement bid in their decisions. While EU citizens value cost-effectiveness and domestic favouritism, most support sustainable procurement objectives.

Vluggen et al. [126] explore how external forces can hold municipalities accountable for sustainable procurement through in-depth document analysis and 34 semi-structured interviews in three mid-sized Dutch municipalities. The results reveal that legal pressure to ensure sustainable procurement is limited. Due to the absence of sanctions for noncompliance, national laws, guidelines, and principles are deemed non-binding. After Vluggen et al. [126], several streams of research on green public procurement are observed. For example, Miyamoto et al. [83] aim to determine the areas in which it is more straightforward or challenging for local municipalities to adopt green purchasing and to identify the extent and role of green purchasing policy in encouraging green purchasing. According to the authors, green public procurement is related to higher adoption and measurement rates of green purchasing.

Moreover, Oliveira et al. [89] identify and classify the stakeholders in the sustainable procurement system of Brazilian public entities. Although governmental and intra-organisational stakeholders are seen to be more significant, specific stakeholders deemed essential by the literature and by experts are considered less significant by organisations. Simion et al. [114] analyse the most important green procurement barriers and enablers for building projects in Romania and group them into clusters. The research results show that technical and technological issues associated with using green building materials represent the most significant barrier. Other barriers also include the increase in project execution costs, while the enablers for green public procurement consist of higher energy efficiency, the use of green building materials, and the pressure to enact environmental protection policies or legislation. Moving further in this direction, Khahro et al. [60] quantify the factors contributing to the adoption of green procurement in construction projects and find that market factors and techniques have an important role in improving green procurement acceptance and implementation. Hamdan et al. [48] employ an in-depth case study of actual sustainable neighbourhood (SN) development in Norway to investigate green procurement in SN initiatives. Finally, Vejaratnam et al. [125] review the barriers hampering the application of green government procurement based on 29 studies from the Web of Science and Scopus databases. The authors consider a lack of knowledge and awareness as the most significant obstacles to green government procurement, whereas budgetary limitation is a minor obstacle.

Overall, the previous analysis reveals several insights. First, the research mainly focuses on the drivers and barriers to adopting green public procurement. Second, there is a focus on examining green public procurement practices in China and some European countries such as Sweden, Italy, Norway, Italy, the Netherlands, and Romania. Third, studies concentrate on applying green procurement in municipalities, local governments, and construction projects.

Unlike the forward local main path, the backward local main path shows multiple papers at the start. For instance, van Calster [123] points out that governments play an increasingly important role in the market economy, as purchasers and regulators, using their purchasing power to further environmental and social goals. Two years later, McCrudden [78] provides a deep understanding of how public procurement can advance social objectives, such as promoting equality and human rights. Günther and Scheibe [47] analyse the factors that hamper green procurement and conclude that environmental awareness and friendliness are necessary to broadly achieve green procurement, industrial ecology, and sustainable development. In addition, Thomson and Jackson [118] find that green procurement can be promoted through legislation and implementing new action plans to embed green practices in government procurement. McCrudden [78], Günther and Scheibe [47], and Thomson and Jackson [118] merge with Walker and Brammer [128], which examines sustainable procurement in the UK public sector and reveals a significant variation across public sector entities in terms of sustainable procurement practices. Preuss [93] looks at how local government agencies in England employ their procurement activities to foster sustainable development.

Ho et al. [50] investigate the procurement activities and policies of five Asian nations and Hong Kong. They emphasise the importance of government involvement and up-to-date information resources in the overall effectiveness of green procurement and its performance. In Brammer and Walker [17], a systematic and comprehensive examination of how public bodies adopt sustainable procurement globally and the primary situational elements influencing participation in sustainable procurement is conducted. The previous papers end at Walker and Brammer [127], which looks at the relationship between sustainable procurement and e-procurement in the public sector and finds that e-procurement and communication with suppliers can support sustainable procurement’s environmental, health, labour, and safety dimensions. Prier et al. [94] develop a sorting framework to evaluate whether certain firms are systematically more inclined to undertake sustainable public procurement activities than others. The authors’ findings suggest that agencies of different reach and scope do not vigorously pursue sustainable public procurement initiatives.

Nevertheless, when they apply sustainable public procurement, their efforts tend to be very diverse between and within government levels and organisational size. Strongly connected to the previous article, Roman [109] examines the conditions under which an organisation is ready to engage and promote sustainable procurement practices and identifies whether a top executive’s leadership style can reflect the extent to which sustainability is stimulated within the organisation. The empirical analysis shows that the top executives’ leadership style positively correlates with the likelihood that an agency will participate in sustainable procurement procedures. Subsequently, Leal Filho et al. [65] research the drivers and challenges that higher education institutions face when adopting sustainable procurement practices. The authors argue that much work is required to support the uptake of sustainable procurement policies and practices across all functions in higher education institutions. Beyond the education sector, Yu et al. [133] summarise the literature on e-procurement and sustainable procurement in the construction sector. Bucea-Manea-țoniș et al. [18] also conduct a literature review of the barriers to adopting green public procurement and incorporate a case study on green agriculture in Romania. Finally, Li et al. [67] examine sustainable supplier selection in public–private partnership projects and develop a sustainable supplier selection system considering five factors. According to the authors, the suppliers’ sustainable financial capabilities and technology solutions are crucial considerations when selecting a sustainable supplier.

To summarise, articles on backward local main paths play a crucial role in sustainable public procurement knowledge diffusion. Regarding content, there is a slight difference between the papers appearing on the paths. The backward local main path shows that, at the start, articles focus on the role of public procurement in fostering environmental and social sustainability. Then, the focus shifts to examining sustainable public procurement and the factors influencing its implementation in different geographic contexts. Finally, the focus ranges from e-procurement to sustainable public procurement in the construction, education, and water resources sectors.

The Analysis of the Global Main Path

The preceding paths focused on discovering the important local links within the citation network. In contrast, the global main path can decide the path with the most influence. Figure 7 depicts the global main path with 14 noteworthy documents. Table 2 displays the SPC value of each link. As can be observed, the link from Walker and Brammer [128] to Preuss [93] has the highest SCP, followed by the link emanating from McCrudden [78] to Walker and Brammer [128], the link from Günther and Scheibe [47] to Walker and Brammer [128], and the link from Thomson and Jackson [118] to Walker and Brammer [128]. The connections near the end of the journey are far thinner than the ones at the beginning, showing that older publications got a great deal of attention while more recent pieces garnered very few citations. Nonetheless, articles near the end of the global main path indicate their significance among the citation network’s followers. As new articles continue to appear, these articles’ positions must be assessed over time.

Fig. 7
figure 7

The global main path

Full size image
Table 2 The SPC values of all links in the global main path
Full size table

The Analysis of the Key-Route Main Path

The historical evolution of green procurement research is shown in more depth by analysing the key-route main path. Figure 8, which displays the structure of green procurement research, shows the key-route main path. This path contains practically all global and local main paths, except for seven additional articles. This section is devoted to analysing these papers for further insights into green procurement research.

Fig. 8
figure 8

The key-route main path

Full size image

The first new article on the left path, Bohari et al. [16], reports preliminary results of green procurement practices in Malaysia and argues that construction stakeholders do not widely use them despite green procurement guidelines and considering green criteria in bidding processes. In the following paper, Yang et al. [131] apply the theory of planned behaviour to analyse the issues of developers’ green procurement in the construction industry. According to the findings, subjective norms and perceived behaviour control elements substantially affect developers’ green procurement behaviour attitudes. In the following paper, Grandia and Voncken [44] investigate the relationship between motivation, ability, and opportunity and six different types of sustainable procurement, including green public procurement, bio-based public procurement, and innovation-oriented public procurement. Finally, AlNuaimi et al. [5, 6] adopt the natural resource-based view theory to analyse the impact of leadership styles and innovation capability on green procurement. Their results show that transformational or transactional leadership styles do not impact green procurement, despite their influence on innovation capability.

The right path comprises three new papers. In the first paper, Miemczyk et al. [80] make a systematic literature review of sustainability in purchasing and supply management, going beyond the typical environmental and social sustainability scope. More specifically, the authors report two different trends in the literature: internal or dyadic issues and an emphasis on ecological rather than social sustainability.

In addition, a survey of studies on green supplier selection conducted by Igarashi et al. [55] reveals that researchers have focused mostly on creating normative decision models for use in the latter stages of the selection process. The authors also draw the conclusion that there is a lack of consistency in the study on green supplier selection and highlight the risk of excessive focus on technical factors. Finally, Appolloni et al. [7] review the literature related to green procurement in the private sector and determine the following three overarching themes in green procurement: (a) what motivates and drives its use,(b) what hinders its spread; and (c) what performance gains result from its implementation. In summary, the key-route main analysis provides more detailed information concerning the implementation of green procurement in the construction industry and the relationship between green procurement and innovation. Moreover, the path uncovers several seminal reviews discussing sustainability in purchasing management, green supplier selection, and implementing green procurement in the private sector.

Discussion

Using a combination of a keyword co-occurrence network analysis and a citation network based on 452 articles, this study seeks to analyse the primary subjects in the area of green procurement. Four alternative paths are built off of the biggest subnetwork to explore the information dissemination processes in the green procurement sector from various vantage points. Forward and backward examination of local main paths provides a clear depiction of the evolution of this academic topic across time. Furthermore, the most influential path is identified using the global main path, and the extensive development structure of the green procurement domain is shown using the key-route main path analysis.

The main findings can be summarised based on the analysis of these quantitative approaches. First, the keyword co-occurrence network analysis results show that green procurement research mainly focuses on several topical themes, including green supply chain management, sustainable public procurement, sustainability, green supplier selection, and environmental management. Research about green procurement in promoting sustainable development occupies a high percentage. As a sustainable practice, green procurement is considered a means of sustainable development due to its impact on the environment, society, and the economic conditions of firms delivering or receiving green products and/or services. The issues posed by sustainable development put the procurement function under pressure to improve environmental performance, reduce waste, and increase resource efficiency. Related keywords to green procurement include sustainability, sustainable procurement, environmental concerns, and green manufacturing.

In the context of green supply chain management, green procurement emerges as a cornerstone of sustainable operational practices [111]. It represents an actionable strategy organisations can adopt to align their operations with environmental sustainability. As a key process within the overall supply chain, procurement activities, from sourcing to buying, can profoundly impact the ecological footprint of an organisation [68]. When implemented effectively, green procurement policies enable organisations to select and prioritise suppliers that comply with environmental standards or demonstrate superior environmental performance [15, 77]. These choices can significantly reduce the organisation’s supply chain’s environmental impact and reduce carbon emissions, waste generation, and overall resource consumption [36, 52, 61]. Moreover, green procurement is a key lever for broader systemic change within the supply chain. It can influence suppliers upstream to adopt more sustainable practices, driving a ripple effect of sustainability improvements throughout the supply chain. Downstream, procuring environmentally friendly products and services can enhance the market’s demand for green offerings and accelerate the shift towards sustainability. Thus, green procurement is not merely a stand-alone activity but a strategic function that permeates the entire supply chain and shapes its environmental performance [85]. Consequently, the role and impact of green procurement extend far beyond operational efficiency and cost-effectiveness, contributing significantly to the organisation’s broader sustainability objectives and shaping the discourse on green supply chain management.

Given the importance of green procurement in government operations, studies about green public procurement’s implementation opportunities and challenges have captured scholars’ attention. Sustainable public procurement policies have recently been researched in different sectors, such as construction, education, and agriculture. It is critical to draw attention to the role of government policies in driving wider green supply chain practices. Through their procurement policies, governments can significantly influence private sector behaviour towards more sustainable practices [101]. However, leveraging public procurement towards minimising global climate change and realising a circular economy is still an intriguing research area that deserves further attention.

Given the necessity of sustainable public procurement policies, it becomes clear that green procurement is not just an adjunct to green supply chain management; it serves as a critical driver for confronting climate change and fostering circular economy practices [98]. In the context of climate change, the push towards green procurement can significantly contribute to reducing greenhouse gas emissions. The decision to favour suppliers demonstrating responsible and environmentally friendly practices encourages a broad-based shift towards low-carbon technologies and renewable energy sources within the supply chain, promoting decarbonisation. Additionally, green procurement bolsters circular economy principles by advocating for sourcing recycled or recyclable materials, minimising waste, and endorsing the reuse and refurbishment of products [57]. By doing so, green procurement enables organisations to depart from the conventional linear economic model of “take-make-waste,” advocating instead for a “reduce-reuse-recycle” approach that improves resource efficiency and sustainability [58].

Despite the recognised role of green procurement in governmental operations and its potential to induce more sustainable practices in the private sector, leveraging public procurement to mitigate global climate change and facilitate a circular economy remains an underexplored research area [101]. With a growing focus on sustainable development goals, the role of green procurement transcends its operational implications. As a result, green procurement can serve as a transformative mechanism within the green supply chain, with impacts reaching far beyond organisational boundaries to include a global economic scale. This underlines the profound influence organisations, particularly governmental bodies, hold in instigating environmental transformation within their operations and supply chains [23]. It also emphasises the belief that economic prosperity and sustainability are not merely compatible but can serve to enhance one another in a symbiotic relationship.

By methodically analysing green procurement research’s four major paths over the last several decades, we can see which studies have impacted the field’s growth most. Based on the distribution of the major branches, the local main path reveals how previous studies have mostly ignored the private sector in favour of investigating green government procurement in both developed and developing nations (e.g., the UK, Sweden, Norway, and China). With the passage of years, research shifted to exploring e-procurement in the public sector and the determinants of sustainable public procurement initiatives in different geographic contexts such as Romania and Brazil. In addition, the local and global main paths are consistent, and the findings highlighted that public procurement had been the main focus over the last two decades. The global main path shows two influential studies, Walker and Brammer [128] and Preuss [93], which discussed sustainable public procurement from the UK perspective.

After analysing the most influential articles in green procurement, we revealed additional ideas by analysing the key-route main path. The following are the findings: First, the number of articles about green public procurement is proliferating, with topics including green procurement implementation in the construction sector, supplier selection, innovation, and green private procurement. As more articles are added to the citation network, the findings can be updated rapidly, and articles on the key-route main path should be checked periodically.

Conclusion

Significant attention has been paid to green procurement in the past two decades. As a result, there is a need to examine the green procurement field comprehensively and systematically and offer valuable insights for future research. Based on 452 journal articles extracted from the Scopus database, this study attempts to provide insights into green procurement research from a dynamic perspective. Specifically, this work uses a keyword co-occurrence network to determine the most prevalent themes in the scholarly literature. Additionally, the article analyses local (both forward and backward), global, and key-route main paths of knowledge transmission in the green procurement area. Using this approach, the novel aspects of this study can be found. First, the primary hotspots in green procurement are identified and investigated. Second, this is the first attempt to use MPA to describe the entire evolutionary process of green procurement. Thirdly, applying these quantitative methods facilitates the exhaustive and methodical inspection of many green procurement-related articles.

To the author’s knowledge, no study has analysed the development of green procurement research based on keyword co-occurrence clustering and MPA. This paper contributes by assisting academics and practitioners in comprehending the fundamental aspects of green procurement research holistically. In addition, the paper provides useful references for determining which publications shaped and contributed to the development of the field. The application of MPA aids in acquiring the most seminal studies in the history of green procurement research effectively and objectively. With the support of this new technique, this study provides readers with novel insights into the mainstream literature, the flow of ideas, the changes in research themes, and the potential research directions. This novel research framework can be expanded to examine the evolution of knowledge in other research domains.

Implications and Future Research

The increasing number of articles in the field of green procurement indicates that the potential for future growth is substantial. It is essential to critically investigate the potential contribution of green procurement to lessen the alarming impacts of climate change [1, 73]. Green procurement research has been incorporated into diverse fields, including environmental science, business management, operations research, social science, and marketing. Soon, there is a need to expand collaboration as the multi-disciplinary nature of green procurement necessitates researchers from other disciplines to deal with green procurement challenges effectively. Analysing the keywords used frequently in the selected sample, it can be inferred that research on green procurement and sustainable development will be studied further. Clarifying the incentives prompting organisations to embrace green procurement strategies is necessary considering financial pressure and market dynamics. Adding sustainable development to the organisation’s competitive priorities may also result in a network change involving business and non-business actors like the government, media, and regulatory bodies [25]. As a result, future studies should examine how to form collaborative ties between these actors to ensure the successful contribution of the organisation to sustainable development. Moreover, the topic of sustainable public procurement stands out extensively. In the future, studies on the behaviour of public procurers and their commitment to environmental knowledge and sustainability are required to facilitate the application of greening practices in the public sector.

The findings of the MPA reveal numerous future research directions. Green procurement research has expanded to include the study of private green procurement, for instance, in light of the heightened focus on negative environmental impacts and social issues. To this end, researchers can investigate this topic in greater depth. In addition, the end of the local main paths pointed to the importance of green procurement in sustaining the healthcare and education sectors. In the future, researchers should study incorporating sustainability values into the procurement function of other equally important sectors such as tourism, transportation, agriculture, and minerals. This is because industries have different characteristics which can facilitate or impede the implementation of green procurement. Integrating other theories and their combination with practice will undoubtedly enrich the knowledge base of the green procurement field and help solve sustainable development and environmental sustainability problems. Additional practical-oriented research on green procurement is recommended by increasing collaboration between academics and industry practitioners.

Research Limitations

Although this article attempts a comprehensive analysis of the green procurement field, it fails to address a few deficiencies. First, the findings of the keyword co-occurrence network analysis and the MPA depend on the sample that was picked. In this analysis, we only looked at journal articles indexed in the Scopus database. As a result, it is possible that the study does not accurately portray how the green procurement field evolved. Although the four primary paths uncovered the knowledge transmission routes from various angles, it is possible that some significant articles were overlooked by utilising this technique. Research into the content and information diffusion paths in different areas of green procurement might therefore use more clustering approaches beyond MPA in the future.