A resource-based view of green innovation as a strategic firm resource: Present status and future directions

Green innovation could become a valuable firm resource for establishing competitive advantage while simultaneously contributing towards sustainable development; in other words, green innovation has the potential to address the dilemma between consuming available resources and preserving them for the future. However, there is a dearth of studies systematically examining the present structure and future scope of research on green innovation as a firm resource. Seeking to explain the sustainable development dilemma of green innovations through the theoretical perspective of the resource-based view of the firm, we address this gap with a comprehensive bibliometric analysis of 951 relevant articles. The key contributors to the extant literature are recognised with bibliographic coupling, citation analysis and co-authorship analysis. A co-citation analysis identifies four major thematic areas of research: green supply chain management, green product design, corporate environmental responsibilities and social sustainability. Further, a dynamic co-citation analysis tracks the pro-gression of these thematic areas. Content analysis of the thematic areas provides insights into the status of the research domain. This study also contributes to the extant literature by identifying prestigious articles on green innovation as a firm resource, analysing the co-occurrence of keywords and suggesting future research agendas.


| INTRODUCTION
Increased public awareness that current economic progress compromises the availability of resources for future generations has compelled businesses and firms to think beyond profit maximisation (Brulhart et al., 2019;Chen et al., 2012). Large multinational firms, such as Coca-Cola, DuPont, Kellogg's and many others, have responded to this public demand by recruiting chief sustainability officers who are responsible for designing suitable sustainable development strategies (Fu et al., 2020). Such strategies are often evaluated via an accounting framework that focuses on the triple bottom line-the economic, environmental and social performance of the firm (Goh et al., 2020;Tate & Bals, 2018). According to Galbreath (2019), a firm's sustainable development is guided by the strategic endowment of resources, including specialised routines, dynamic capabilities and organisational assets. Influenced, in particular, by the United Nation's sustainable development goals (SDGs), many multinational enterprises are proactively implementing suitable strategies that encourage green innovations to achieve sustainable development (Ogbeibu et al., 2021;Van der Waal et al., 2021). Green innovations aim to design products that consume less energy and require fewer raw materials to manufacture (Dangelico & Pujari, 2010), reduce adverse environmental effects when used (Dangelico, 2016) and can be easily recycled post usage (Dangelico et al., 2017). The postulation of green innovation as a strategic firm resource may address many social and environmental issues related to sustainable firm practices (Du et al., 2018;Duque-Grisales et al., 2020).
Green innovation as a firm resource may bestow sustainable competitive advantages from reduced manufacturing cost (Han et al., 2019), customers' positive attitude towards the brand (Olsen et al., 2014) and increased compliance with regulatory requirements (Hall, Matos, Sheehan, et al., 2012). However, successfully leveraging green innovation as a strategic resource may require buyer-driven knowledge transfer mechanisms and knowledge acquisition capabilities within the firm (Awan, Arnold, et al., 2021;Awan, Nauman, et al., 2021), investment in research and development (Duque-Grisales et al., 2020), support from top management to establish technological capabilities Forcadell et al., 2021), cross-functional integration within the firm, development of a network of strategic partners (Dangelico, 2016) and implementation of green marketing programmes (Han et al., 2019). Firms, on the one hand, recognise sustainability initiatives for developing strategic resources from committed relationships with stakeholders and a positive reputation for the firm (Bangsa & Schlegelmilch, 2019;Brulhart et al., 2019;Gunarathne et al., 2021). For instance, firms prioritising sustainability initiatives often receive an optimistic assessment from financial analysts, which, in turn, helps attract long-term investments (Durand et al., 2019;Jia et al., 2020). On the other hand, firms often abstain from investing in sustainability initiatives to save resources required to survive contemporary market competition (Kim, Wan, et al., 2019), especially in the absence of risks from government interventions (Tian et al., 2019) and stakeholder pressures (Christmann, 2004). Consequently, firms face a trade-off between reaping benefits from resource consumption in the present and preserving resources to enable long-term future benefits (Ambec & Lanoie, 2008;Barnett & Salomon, 2012;Kim, Bansal, et al., 2019).
In the extant literature, the resource-based view (RBV) offers a suitable theoretical perspective to address this trade-off (Galbreath, 2019;Guesalaga et al., 2018;Stefanelli et al., 2021). The RBV conceptualises a firm as a pool of resources and capabilities that provides a sustained advantage over competitors and delivers superior performance to the firm (Barney et al., 2001;Guesalaga et al., 2018). The firm may sustain its competitive advantage when these resources and capabilities are valuable, rare, not perfectly imitable and non-substitutable (Barney, 1991). In later iterations, the RBV replaced the requirement of non-substitutability with organisation, which referred to the firm's ability to exploit resources or capabilities that are valuable, rare and not perfectly imitable (Barney, 1995). The resources a firm requires to achieve sustainable competitive advantage depend on the firm's relationship with the natural environment (Hart, 1995) and social well-being (Tate & Bals, 2018).
Recent studies highlight that a proactive environmental strategy may mediate the relationship between a firm's environmental capabilities and its competitive advantage (Chan, 2021;Mishra & Yadav, 2021). Higher-order resources, such as accurate business forecasts and strategic planning, may deliver sustained competitive advantage to a firm through its operating resources, such as specialised production plants, brand names, loyal customers and patents (Wibbens, 2019). Barney (2018) also contends that a firm's profit appropriation may encompass the perspectives of social communities and the natural environment beyond those of more direct stakeholders, such as shareholders, suppliers, employees and customers. Therefore, the RBV may aptly explain the ways in which green innovation as a firm resource potentially addresses the trade-off between resource consumption and resource preservation.
Research on green innovations as firm resources has assumed increasing importance in the contemporary literature and in the corporate world (Du et al., 2018;Duque-Grisales et al., 2020;Galbreath, 2019). However, the extant literature has, thus far, failed to provide a comprehensive understanding of RBV-guided research on green innovation as a firm resource. The current study fills this The major contributions of this study to the literature on green innovation and sustainable development are threefold: First, the study identifies the key contributors shaping the literature on RBVguided green innovation as a firm resource by performing a rigorous bibliometric analysis of a host of relevant journal articles (Fahimnia et al., 2015). We conducted bibliographic coupling, citation analysis, prestige analysis and co-authorship analysis, which are wellrecognised techniques for their ability to identify the key contributors towards a research topic (Xu et al., 2018). Second, the study identifies important thematic areas from the prior research on RBVguided green innovation as a firm resource by clustering articles using a co-citation analysis (Caviggioli & Ughetto, 2019). Subsequently, we trace the evolution of the thematic areas by applying a dynamic co-citation analysis (Xu et al., 2018). Third, a content analysis of prestigious articles within each thematic area highlights important elements of debate from previous studies and proposes relevant future research agendas. We submit these agendas for advancing the discourse on green innovation as a firm resource and, thereby, contributing to the literature. As the earliest bibliometric analysis of the literature on RBV-guided green innovation as a firm resource, this study organises the fragmented literature and, hence, should help researchers navigate the field. Thus, in addition to providing important insights to managers, the study's findings may spur further research in the domain. This paper is organised into eight sections. The second section presents the methodology we followed to select relevant studies for analysis. The next three sections present findings from the bibliometric, thematic and content analyses. The sixth section discusses the findings and recommends future research agendas. The seventh section highlights the theoretical and practical implications before the paper's conclusion in the eighth section.

| METHODOLOGY
Bibliometric research assesses the social and structural connections among various research constituents by deploying quantitative techniques on bibliometric data to determine the philosophical underpinnings of a research domain (Broadus, 1987;Khanra, Dhir, Kaur, et al., 2021). In the business and management discipline, bibliometric research has risen in importance as a method to present organised contributions, provide a comprehensive perspective, uncover knowledge gaps and generate new research ideas (Donthu et al., 2021). Compared to alternative methods for summarising existing literature, a bibliometric study is better suited to address the research gaps in the literature on RBV-guided green innovation as a firm resource. For instance, the systematic literature review is one alternative method to gather, organise and evaluate the existing literature based on the manual evaluation of a limited number of publications (Snyder, 2019). Thus, systematic literature reviews are ideally equipped to qualitatively summarise fewer publications on niche research topics (Donthu et al., 2021;Snyder, 2019). Meta-analysis is another method to explore the direction and intensity of associations among variables by aggregating prior empirical findings (Aguinis et al., 2011). The heterogeneity of previous research, as well as the possibility of a publication bias, however, might jeopardise the veracity of a meta-analysis's findings (Aguinis et al., 2011;Donthu et al., 2021).
This study followed a structured protocol for bibliometric study (see Figure 1), which Khanra et al. (2020) developed from prior literature. The literature selection in the protocol proceeded through three sequential stages: scanning, curating and analysing a sample profile (Khanra et al., 2020). From a methodological standpoint, this protocol includes important quantitative techniques to analyse bibliometric data, such as bibliographic coupling, citation analysis, prestige analysis, co-authorship analysis, co-word analysis, co-citation analysis and dynamic co-citation analysis (Khanra et al., 2020). Finally, we employed content analysis of thematic areas identified from cocitation analysis to report the key intellectual capital of each thematic area, sub-themes within each thematic area and actionable future research agendas (Khanra et al., 2020).

| Scanning phase
Scopus is a comprehensive database that covers a wide range of academic documents on topics of intellectual interest (Caviggioli & Ughetto, 2019;Khanra, Dhir, Parida, et al., 2021). Thus, we began locating publications pertaining to this study by searching the titles, keywords and abstracts of the Scopus database for pre-determined terms: 'resource-based view' and 'green innovation'. However, a preliminary exploration of Scopus revealed 'green product innovation', 'sustainability' and 'sustainable development' as related terms that are frequently used along with 'green innovation'. Accordingly, we modified the search string as follows-'resource-based view AND green innovation OR green product innovation OR sustainability OR sustainable development'-and found 1662 articles published in English through 31 July 2021. The sources of the articles were indexed journals in business management and related subject areas.

| Curating phase
The authors carefully read the abstracts of all articles that appeared in the scanning phase and removed 711 articles that did not directly focus on green innovations as firm resources. Thus, a total of F I G U R E 1 Protocol for a bibliometric study (this protocol was prepared by Khanra et al., 2020) 951 articles comprised the sample for this study. We exported the sample information in .ris and .csv formats for further analysis.

| Analysing phase
A total of 2468 authors from 1734 organisations in 99 countries published the 951 articles identified from 393 journals. The earliest articles were presented in 1990, which suggests that the concept of green innovation as a strategic firm resource emerged in management and related domains over the past three decades. However, more than 71% of the articles (682 articles) were published since 2015 (see Figure 2), establishing current research interest in the concept.  (Caviggioli & Ughetto, 2019). The logic of this technique is that a pair of articles shares common intellectual capital when the articles have a larger number of common references (Xu et al., 2018). While backward citation tracing can provide a useful overview of a topic, it is criticised for its inability to aggregate older articles . As a result, scholars frequently employ citation analysis-an approach based on forwarding citation tracing-to supplement the findings from bibliographic coupling (Khanra, Dhir, Parida, et al., 2021). The present study acknowledges the influential authors who made important intellectual contributions to the sample used for the study (see Table 3). We conducted bibliographic coupling with the help of VOSviewer software to rank the key contributing authors with respect to the total link strength, which represents the total number of bibliographic links with respective elements of analysis (Van Eck & Waltman, 2014). This study followed the fractional counting of links to reduce the impact of a number of co-authors for an article (Khanra et al., 2020). Table 3 lists the influential authors who made important intellectual contributions to the sample used for this study. Bag and Gupta are the most influential authors in the literature on green innovation as a firm resource followed by Liu, Jabbour and Childe.

| Citation analysis
Citation analysis seeks to assess the academic acceptability of research by counting the frequency with which studies have been cited in different publications (Khanra et al., 2020). Citation analysis findings frequently supplement bibliographic coupling findings (Fahimnia et al., 2015). Table 4 lists the top 10 authors who contributed popular articles to this study's sample. Seuring tops the list of the most popular authors ordered by total link strength from citation analysis using VOSviewer; Chen, Li and Barney follow. However, citation analysis assesses only the popularity of an article among others in a sample and not its importance in a research domain .

| Prestige analysis
The number of times highly acclaimed articles cite a particular article determines the cited article's prestige (Khanra, Dhir, Parida, et al., 2021).
Thus, prestige analysis identifies articles that play a significant role in the development of a body of literature. An extended version of the original PageRank algorithm developed by Brin and Page (1998) can be used to investigate the prestige of articles (Xu et al., 2018).
Through iterations, this technique locates articles that are co-cited with highly co-cited publications (Fahimnia et al., 2015). Recognising its capacity to implement a robust scoring system, we utilised Gephi for prestige analysis (Khanra, Dhir, Parida, et al., 2021). Table 5 T A B L E 2 Top 10 journals based on number of publications and bibliographic coupling lists the top 10 prestigious articles from a total of 951 articles in our sample.

| Co-authorship analysis
Based on the degree of collaborative publications, co-authorship analysis reveals collaboration trends among authors engaged in a field of research (Caviggioli & Ughetto, 2019). Authors who are part of a collaborative network are more likely to mention related articles. Hence, such networks are important within a research field (Khanra et al., 2020), and the results of co-authorship analysis are complementary to those of other bibliometric methodologies . This method, however, is unable to detect the efforts of single authors (Khanra, Dhir, Parida, et al., 2021). To emphasise the most important collaborations, we selected articles with at least 10 citations in Scopus for this study. VOSviewer is a powerful tool for analysing large datasets (Fahimnia et al., 2015), ing keyword co-occurrences from bibliometric data (Fahimnia et al., 2015;Van Eck & Waltman, 2014), we employed it to conduct a co-word analysis. The authors of the articles in this study's sample contributed 3114 keywords (94 of which co-occurred more than five times), while publishers indexed the articles using 2864 keywords (252 keywords co-occurred more than five times). Tables 6 and 7 present the top 10 author and index keywords, respectively, from the co-word analyses. Figures 4 and 5

| Co-citation analysis
A more advanced technique, co-citation analysis detects thematic commonalities across papers in a certain research field (Khanra, Dhir, Parida, et al., 2021). When two articles are cited by another two articles, the later pair of articles is considered co-cited (Xu et al., 2018).
Co-cited articles form an important literature network within the research field (Fahimnia et al., 2015). The Louvain algorithm in the Gephi modularity tool aptly detects important clusters from the literature network through iterations

| Dynamic co-citation analysis
A dynamic co-citation analysis facilitates deeper comprehension of the expansion of thematic areas discovered by co-citation analysis (Fahimnia et al., 2015;Xu et al., 2018). Gephi possesses the distinctive functionality required to perform dynamic analysis on the findings from co-citation analysis (Xu et al., 2018). Figure 6 depicts the history

| CONTENT ANALYSIS
From the content analysis of the articles listed in Tables 8-11, we identified four thematic areas, each connecting the articles within a cluster. These thematic areas are green innovations for supply chain management, green product design, corporate environmental responsibilities and social sustainability. In addition, the content analysis of  prestigious articles in each thematic area revealed sub-themes, which we also discuss below.

| Thematic area 1: Green supply chain management
Green supply chain management pays due attention to environmental concerns in decisions related to firms' logistic operations to achieve sustainable development (Gold et al., 2010;Golicic & Smith, 2013). Hart (1995) introduced a natural resource-based view of the firm, which directed businesses to deploy three interlinking strategiespollution prevention, product stewardship and sustainable development-to achieve competitive advantage. Fowler and Hope (2007) advocate for the parallel implementation of these strategies to better achieve the SDGs. To this end, the adoption of green operations strategies would require specific supply chain capabilities embedded in a sustainable supply chain (Liu et al., 2017). Green supply chain management may further encourage green manufacturing, green design and green purchasing (Liu et al., 2017).
Prior studies have explored the importance of establishing green supply chain management as a resource in different industries. Studies of the ostensibly 'polluting industries', such as apparel (Fowler & Hope, 2007), automobiles (Liu et al., 2017) and electronics (Huang & Yang, 2014), have further highlighted this importance. Shi et al. (2012) uncovered the causal impact of institutional drivers, performance measures and intra-organisational and inter-organisational practices on green supply chain management. Here, we discuss the relationship of green supply chain management with three aspects often studied in the context of sustainable development: the circular economy, competitive advantage and collaborative advantage.

| Circular economy
A circular economy is an economic system in which a cyclical model for material flow reduces negative environmental impacts and stimulates new business opportunities (Huang & Yang, 2014;Miemczyk et al., 2016). Unlike the traditional linear throughput flow model, a circular economy emphasises reusing, remanufacturing, refurbishing, upgrading and repairing as well as utilising renewable and wastederived energy throughout the value chain (Huang & Yang, 2014;Miemczyk et al., 2016). To this end, companies may develop strategic resources to advance technology, knowledge and relationships by designing closed-loop supply chains to circulate raw materials, components and used products (Miemczyk et al., 2016). Reverse logistics innovation is one such strategic decision gaining traction among businesses (Huang & Yang, 2014;Miemczyk et al., 2016).

F I G U R E 4 Co-occurrences of author keywords [Colour figure can be viewed at wileyonlinelibrary.com]
However, these strategic resources are sensitive to changes in the business environment (Miemczyk et al., 2016). For instance, institutional pressures from regulators and actions by competitors and customers may moderate the association between reverse logistics innovation and environmental performance (Huang & Yang, 2014).
However, the institutional pressures do not ensure enhanced economic performance with reverse logistics innovation (Huang & Yang, 2014).

| Competitive advantage
The literature suggests that firms are increasingly struggling to identify sources from which to gain competitive advantage, especially in hypercompetitive environments (Markley & Davis, 2007). In such cases, the establishment of a green supply chain may contribute to the development of a competitive advantage (Gold et al., 2010;Markley & Davis, 2007). For instance, green supply chain management saves firms costs by reducing their consumption of natural resources, water and energy (Gold et al., 2010). Overall, green supply chain management may enhance firm performance in terms of market, operational and accounting factors (Golicic & Smith, 2013).

| Collaborative advantage
Inter-firm knowledge exchanges for selecting and monitoring suppliers may result in greener process management and supply chain management (Gavronski et al., 2011). Historically, such strategic knowledge exchanges often emerge from inter-firm collaborations aimed at addressing social and environmental issues; hence, competitors find these exchanges imperfectly imitable (Gold et al., 2010)

| Eco-innovations
Firms often promote eco-innovations to adhere to government regulations and consumer pressures (Lin et al., 2014), and these innovations often manifest in product designs, manufacturing processes and organisational cultures (Cheng et al., 2014). Though firms expect eco-innovations to deliver significant profitability and legitimacy (Li et al., 2017), the environmental orientation of a firm may not directly result in superior firm profitability (Zhang & Walton, 2017). Cainelli et al. (2015) suggest that internal resources deployed in research and development and employee training are critical to spurring eco-innovation. However, a study by Lee and Min (2015) found a negative relationship between investment in research and the development of eco-innovations and carbon emissions. In fact, eco-friendly innovations at the organisational level have a stronger effect on firm profitability than do such innovations at the product and process levels (Cheng et al., 2014). Overall, eco-innovations tend to be more successful when companies develop organisational capabilities for voluntary self-regulation towards sustainable development (Demirel & Kesidou, 2019). To this end, the environmental orientation of a firm may enhance the positive effect of eco-innovation on firm profitability (Zhang & Walton, 2017).

| Business performance
Firms that commit more organisational resources may achieve better business performance from green product design (Zhang & Walton, 2017). However, the relationship between green product design and business performance is generally complex and uncertain (Lee & Min, 2015;Li et al., 2017). For instance, investment in environmental management systems for adopting green innovation may not yield immediate business performance benefits (Duque-Grisales et al., 2020), but may fuel future business growth from increased research and development for green products (Lee & Min, 2015). In addition, a firm's marketing capabilities may determine the business performance of green products offered by the firm (Amores-Salvad o et al., 2014).

| Knowledge competence
Firms often struggle to balance their sustainability objectives with profitability goals due to uncertain returns from investments in green product design (Cainelli et al., 2015;Zhang & Walton, 2017). Claudy et al. (2016) argue that firms may achieve this balance through a strategic-level sustainability orientation and market knowledge competence. On the one hand, investment in research and development of green products may help firms acquire resources and capabilities to prepare for impending technological shifts towards sustainability (Demirel & Kesidou, 2019). On the other hand, firms may develop the market competence required to address consumer demand for green products (Demirel & Kesidou, 2019). In this regard, Cainelli et al. (2015) suggest that acquiring equipment to leverage knowledge competence

| Thematic area 3: Corporate environmental responsibilities
Corporate environmental responsibilities may include adhering to best practices and international standards, preventing pollution, recycling materials and reducing waste generation (Schoenherr, 2012  , China (Chan, 2005), Germany (Fanasch, 2019) and Sweden (Andersén et al., 2020). The prior research discussed about the reduction of firms' carbon footprints and the benefits and challenges of fulfilling corporate environmental responsibilities in the context of firms' environmental responsibilities (Borland et al., 2016), as summarised below.

| Reduction of carbon footprint
Increasing global warming, climate change and pressures from various stakeholders, such as investors, employees and network partners, have forced firms to reduce their carbon footprints . However, firms that proactively invest in research and development to reduce energy consumption and carbon emissions often achieve superior performance (Alam et al., 2019). For instance, a global study of large multinational companies revealed that the top users of renewable energy consistently exhibited superior financial performance compared to their competitors (Shin et al., 2018).
However, normative or coercive isomorphism for reducing carbon footprints does not exist uniformly among multinational companies across the world due to leniency in interpreting sustainability efforts in many of the host countries where these companies' subsidiaries operate (Escobar & Vredenburg, 2011).

| Benefits of fulfilling environmental responsibilities
Firms fulfilling their environmental responsibilities may develop a sustainable competitive advantage by developing resources for pollution prevention, product stewardship and clean technologies (McDougall et al., 2019). The resulting firm reputation and certifications for environmentally friendly firm practices may translate into superior financial performance (Fanasch, 2019). However, environmentally friendly firm practices may vary with macroeconomic uncertainties, operating mode, firm size and organisational routines (Chan, 2005). For instance, multinational companies with intensive internationalisation as well as research and development programmes are more likely to develop and maintain better sustainability practices (Chakrabarty & Wang, 2012). Colour code Brown Orange Blue Green firms that face resource constraints and strong competition (Andersén et al., 2020). In addition, multinational companies with low intensity for internationalisation as well as research and development may devote inadequate resources to developing and maintaining sustainability practices (Chakrabarty & Wang, 2012). Nevertheless, the environmental orientation of top management may play a key role in whether a firm honours its environmental responsibilities (Andersén et al., 2020).

| Thematic area 4: Social sustainability
Corporate social responsibility (CSR) refers to a firm's commitment to meeting stakeholders' interests in a socially sustainable way (Aguilera et al., 2007;Torugsa et al., 2013). Firms engage in CSR activities, which can be part of their SDGs, to improve people's standard of living (Montabon et al., 2016). Such corporate initiatives may assume a greater role in developing countries, where government initiatives often fail to deliver the desired results (Matten & Moon, 2008). Besides discussing firms' social responsibilities, this thematic area highlights the need for reducing food waste and managing municipal waste.

| Social responsibilities of firms
Firms may benefit society by choosing to volunteer in CSR activities that integrate social issues and business values (Matten & Moon, 2008). In contrast, actors and interest groups at different levels, such as individual employees and national and transnational consumer groups and organisations, often force firms to participate in CSR (Aguilera et al., 2007). Bansal (2005) reported that media pressures often impel corporations to initiate CSR activities. The motives of such actors and interest groups in driving positive societal changes may be analysed from instrumental, relational and moral perspectives, which are concerned with self-interest, relationships among group members and ethical standards, respectively (Aguilera et al., 2007).
Firms with strong CSR performance develop strategic resources and gain competitive advantages by leveraging these resources (Klassen & Vereecke, 2012). These strategic resources help such firms to legitimise their performance claims, differentiate their products and reduce risks to their brand image (Klassen & Vereecke, 2012). For small and medium manufacturing enterprises, proactive CSR may influence financial performance through their capabilities, such as a shared vision, stakeholder management and strategic proactivity (Torugsa et al., 2013). In comparison, a customer orientation for sustainability is of utmost importance in the case of small and medium service enterprises .

| Reduction of food waste
Social sustainability may be achieved by adopting management practices that minimise food waste in multi-tier food supply networks (Mena et al., 2014). Addressing the issue of food waste is critical in developing sustainable food supply chains (Wu & Huang, 2018).
Transparent demand forecasts, improved quality and process control mechanisms as well as improved package designs that extend food products' shelf-lives may significantly reduce food waste while simultaneously improving firm performance (Mena et al., 2014).

| Municipal waste management
Efficient municipal waste management is a critical component of social sustainability at a macro level. Facilitating social mobilisation and retaining environmental integrity are two key determinants of the efficacy of a municipality's waste management systems (Bui et al., 2020). To this end, municipalities must develop capabilities to utilise economic resources efficiently and leverage available technological support (Bui et al., 2020). Building relationships with higherlevel government authorities and networking with other municipalities may be important considerations in implementing a high-performing municipal waste management system (Barrutia & Echebarria, 2015).

| DISCUSSION AND FUTURE RESEARCH AGENDAS
The present study has identified the key contributors shaping the literature on green innovation as a firm resource. Tables 1, 3 and 4 present notable authors. In addition, our examination of co-authorship (see Figure 3) revealed the collaborative networks that are important to the extant literature. The patterns of collaboration imply that studies on this topic are dispersed across four key groups and a large network of authors.
By clustering articles with co-citation analysis, this study highlighted the major thematic areas in the literature on green innovation as a firm resource: green supply chain management, green product design, corporate environmental responsibilities and social sustainability. Tables 8-11 show the prestigious articles in each of the four thematic areas. Subsequently, we employed a dynamic cocitation analysis to track the growth of these thematic areas. We contend that in-depth examinations of the content of these thematic areas would offer valuable additions to the literature on sustainable development, from a broader perspective. In the following subsections, we recommend directions for future research in each of the thematic areas identified.

| Green innovations for supply chain management
Multi-tier supply chain management firms, such as Ikea, are increasing their efforts to achieve sustainability in their supply chains . In terms of purchasing, production, inventory, distribution and logistics, the performance of partners impacts the entire supply chain . Thus, one of the most important issues for firms seeking to establish green supply chains is analysing and choosing suitable supply chain partners Wu et al., 2020). Furthermore, green innovations for supply chain management may aid sustainable business models in a circular economy (Ferasso et al., 2020) and among small and medium enterprises (Filser et al., 2021). Therefore, future researchers should work to develop robust models for the selection of supply chain partners in both linear and circular value chains.

| Green innovations for sustainable product design
At present, profitability from green products is a serious concern for firms. Researchers, therefore, might aid the sustainable development of green products by suggesting ways to develop firm resources for reconceiving products and markets. Further, effective government policies are required to promote companies' green product design and manufacturing . Researchers have argued that the economic slowdown caused by the COVID-19 pandemic may help policymakers implement proactive solutions towards sustainable development (Bruce et al., 2021). To this end, future research could offer useful inputs for policymakers to promote innovations in green product design.

| Green innovations for sustainable firm resources
The application of the RBV may help identify suitable firm resources for incorporating green innovations in firm practices, processes and activities (Dangelico, 2016). For instance, the RBV may help redefine productivity by incorporating environmental sustainability into a firm's practices (Jacobs et al., 2010), which the firm can then communicate to its customers through green marketing campaigns (Han et al., 2019). Further, eco-branding transforms a firm's brand image by adopting sustainable practices (Olsen et al., 2014). Green information technology is the practice of incorporating environmental sustainability in computing (Chan, 2021

| STUDY IMPLICATIONS
According to Bansal (2005), resource-based factors influence corporate sustainable development initiatives, and firms have embraced the RBV-guided sustainable development perspective.
Therefore, business executives have been increasingly conscious of the need to widen their organisations' aims beyond typical financial expectations to include social and environmental goals as well (de Lange et al., 2012;Hoffman, 1999). From this perspective, the present study offers important implications for both theory and practice.

| Theoretical implications
Research focusing on green innovation as a firm resource is scattered across numerous journals, and few studies have examined the current structure and future scope of research in the domain. To this end, this study offers the following theoretical contributions. Second, the study's analysis of co-authorship networks identifies distinct groups of authors while depicting the collaborative links among authors in each group. Importantly, these author groups play a key role in the evolution of knowledge in the field.
Third, the study uses co-word analysis to broadly classify keywords from the articles into three management domains: business strategy, environmental management and green energy. This classification enhances understanding of the domains in which research on green innovation as a firm resource has concentrated over the years and, accordingly, suggests agendas for future research.
Fourth, the co-citation analysis reveals four major clusters with thematic areas: green supply chain management, green product design, corporate environmental responsibilities and social sustainability. The dynamic co-citation analysis that followed shows the number of papers added to each cluster annually, indicating the historical trends of papers published on green innovation as a firm resource.
Finally, a content analysis of the prestigious articles in the four thematic clusters provides a profound understanding of the thematic areas and directions for future research.

| Practical implications
Sustainability has become mainstream in strategic management, with companies frequently emphasising environmental sustainability (Buysse & Verbeke, 2002;Darnall et al., 2010) and CSR (Campbell, 2007;Hull & Rothenberg, 2008). From this perspective, this study entails the following implications for practitioners.
First, the study finds that business strategy, environmental management and green energy are the three management domains in which research on green innovation as a firm resource is predominantly concentrated. The identification of these domains and their widely used keywords provide an indication of the direction of green innovation as a firm resource.
Second, the identification of the four thematic areas-green supply chain management, green product design, corporate environmental responsibilities and social sustainability-may guide decisionmaking by policymakers and practitioners alike. In addition, the thematic areas indicate trends in existing research and capture the evolution of sustainable development practices over time. All four clusters are actively growing, albeit at varying paces. The findings from our dynamic co-citation analysis demonstrate a gradual shift from research interest in green supply chain management to corporate environmental responsibilities. Interestingly, research on green product design grew rapidly during both of these themes' high-growth period, indicating that green product design may complement both green supply chain management and corporate environmental responsibilities.
Third, the four thematic areas identified here resonate well with the findings of Rangan et al. (2015), who noted 'philanthropy', innovations. Thus, the present study has major implications for researchers seeking to advance the literature on green innovation as a valuable firm resource and for corporate policymakers working to promote sustainable development practices through green innovation. However, future research may aim to structure the literature on green product innovation and green process innovation with a narrower focus. Third, the study discussed four major thematic areas: green supply chain management, green product design, corporate environmental responsibilities and social sustainability. We also observed three minor thematic areas comprising 13, 11 and 8 articles relating to green purchase behaviour, sustainable technology transfer and government initiatives for sustainability, respectively. These minor thematic areas may gain prominence in the future and require comprehensive reviews of the related literature.

CONFLICT OF INTEREST
The authors do not have any competing interests to declare.