Circular Economy and Energy Transition: Research Trends, Knowledge Structure, and Future Directions

Abstract

The circular economy offers effective strategies to support the transition from fossil fuels to renewable energy. However, research at the nexus of the circular economy and energy transition remains fragmented across disciplines and lacks a systematic and integrative overview of its intellectual structure and thematic evolution. To address this gap, this study conducts a large-scale bibliometric analysis of 2977 journal articles published between 2008 and 2025 to examine the development, knowledge structure, and global distribution of this field. Performance analysis and scientific mapping are employed to evaluate research output, subject areas, thematic structures, intellectual foundations, journal dissemination, and international collaborations. The results indicate that the circular economy–energy transition nexus is a rapidly growing and multidisciplinary field. It is anchored by conceptual and policy-oriented works and complemented by applied studies on waste management, bioenergy, and decarbonization technologies that directly relate to energy production, conversion, and system efficiency. The geographical distribution shows a multi-pillar but uneven research landscape, with Europe and China emerging as leading contributors, while other regions remain comparatively underrepresented, shaped by regional priorities and collaborative networks. The study highlights emerging research gaps and future directions, offering insights into how circular economy strategies such as resource circularity and waste-to-energy applications can contribute to sustainable and equitable energy transitions and inform future energy-focused research agendas in the context of low-carbon transformation.

1. Introduction

The escalating climate crisis and mounting concerns over energy security underscore the urgent need to reconfigure global energy systems [1]. Rising greenhouse gas emissions, extreme weather events, and the volatility of fossil fuel markets demonstrate that conventional energy models are no longer sustainable [2,3]. Governments and international organizations increasingly recognize that meeting the targets of the Paris Agreement and achieving net-zero emissions by mid-century requires profound systemic change in the way energy is produced, distributed, and consumed [4]. This pressing context forms the backdrop against which scholars, policymakers, and practitioners call for the transformation of energy systems toward more sustainable trajectories [5].

The energy transition, understood as the global shift from fossil-based systems to clean, low-carbon, renewable, and socially just energy systems, has gained significant momentum in recent years. It involves more than technological substitution; it requires systemic change encompassing governance arrangements and institutional transformation [6] as well as social justice considerations in transition pathways [7].

Global investment in clean energy reached a record USD 1.7 trillion in 2023, surpassing fossil fuel investment for the first time [8]. This shift underscores that the energy transition is not confined to one region but is a global endeavor shaped by diverse policy instruments, including regulatory targets, public investment incentives, and national transition strategies, as well as by differing investment flows, and societal priorities.

National and regional policy commitments further illustrate this global momentum and diversity in energy transition pathways. The United States, through the Inflation Reduction Act of 2022, has committed more than USD 360 billion to clean energy projects [9]. China has pledged to peak carbon emissions before 2030 and achieve carbon neutrality by 2060, and it leads the world in solar and wind capacity additions [10]. Emerging economies are also advancing. India has set a target of 50% cumulative installed electric power capacity from non-fossil-fuel-based energy resources by 2030 [11], while Brazil is expanding bioenergy and hydropower [2]. Across Africa, initiatives such as the African Renewable Energy Initiative aim to install 300 GW of renewable capacity by 2030 [12].

Evolved from a niche idea, the circular economy has developed a broad framework applied in policy, infrastructure, and governance [13]. In the context of energy transitions, circular economy principles directly facilitate systemic change by providing strategies for sustainable energy transition by reducing resource dependency and extending life cycles. They also foster regenerative systems and mitigate environmental impacts through recycling, reuse, and recovery in response to resource scarcity [14]. Furthermore, circular economy principles inform product and system design strategies, including approaches that improve durability, reuse, and end-of-life recovery [15]. Emerging research extends to social and governance dimensions and demonstrates that circular economy principles intersect with justice issues in energy transitions [16]. Community-based energy projects and cooperative models for renewable energy demonstrate new modes of collaboration and institutional innovation [17].

Collectively, these contributions reveal the diversity of perspectives within the circular economy–energy transition nexus, underscoring the need for systematic mapping of the field. Given the multidisciplinary scope and rapid growth of this research area, bibliometric analysis is particularly suitable for systematically mapping the large volumes of literature and revealing intellectual structures and thematic patterns. To fill the gap, this study adopts a bibliometric approach to identify the intellectual structure, thematic clusters, and key research trajectories. To systematically explore these developments and organize the fragmented literature, this study addresses the following research questions:

• How has research on the circular economy and energy transition developed over time and across disciplines?
• What are the dominant themes and how have research interests evolved?
• What influential works and intellectual foundations underpin this field?
• How is knowledge disseminated across journals and countries?
• What research gaps remain and what directions should future studies pursue?

The importance of this study lies in its ability to provide a structured overview of a fast-growing and increasingly significant body of knowledge that contributes to both scholarly debates and policy agendas. For scholars, it maps the thematic and intellectual landscape of an emerging interdisciplinary field. For policymakers and practitioners, it highlights how circularity can be leveraged to design resilient, equitable, and sustainable energy systems capable of driving forward the transition to low-carbon societies.

2. Literature Review

The circular economy has become one of the most influential paradigms in sustainability studies, offering a systemic alternative to the traditional linear model of economic growth [18]. At its core, this circular paradigm seeks to eliminate waste, retain value in materials and products, and regenerate natural systems [19,20]. Scholars have conceptualized the circular economy as a technical, institutional, and economic framework requiring systemic coordination across sectors and scales [21,22].

The existing literature has identified several principles that define the circular economy. First, products and systems should be designed to eliminate waste and pollution by addressing externalities upfront through eco-design and closed-loop strategies. Second, materials and products should remain in use for as long as possible through repair, reuse, refurbishment, and recycling. Third, natural systems should be regenerated, ensuring that ecological cycles are preserved and enhanced. Together, these principles highlight the circular economy as more than a waste management strategy; it is a comprehensive reconfiguration of economic processes [23].

For more than a decade, circular economy research primarily addressed material cycles such as waste reduction, product design, recycling, and manufacturing processes [19,20]. Recently, energy has been recognized as a foundational element of socio-economic systems, although it was long treated mainly as an enabling input rather than as a direct object of circularity [24]. This shift has directed attention toward the role of circular economy principles in shaping energy transitions.

Energy transition denotes the transformation of energy systems from fossil-based to renewable, low-carbon, and socially just alternatives. This transformation involves not only technological substitution but also a systemic change in governance, institutions, and social practices [6,7]. Policy frameworks such as the United States’ Inflation Reduction Act [9], the European Union’s Green Deal [25], and China’s carbon neutrality pledges [10] illustrate global strategies to accelerate this transition. Initiatives in emerging economies, including India, Brazil, and the Africa Renewable Energy Initiative, further demonstrate the diversity of pathways shaping energy transitions worldwide [11,12].

From a socio-technical perspective, infrastructures, technologies, and social arrangements co-evolve to enable energy transitions [6,7]. Persistent challenges, such as resource constraints, financial limitations, and equity concerns, continue to impede progress [26]. Circular economy principles provide complementary strategies for addressing these challenges by closing resource loops, regenerating ecological systems, and contributing to more inclusive forms of socio-technical change [27].

The intersection of the circular economy and energy transition is increasingly recognized as an important area of scholarship [23,24]. Contributions come from different domains, and while the field is still consolidating, several broad dimensions can be identified (

Table 1. Synthesis of conceptual dimensions in the circular economy–energy transition literature.

Dimension	Conceptual Focus	Key Issues and Concepts
Resource and material flows	Managing material and energy flows to reduce resource dependency and environmental impacts	Recycling, reuse, and recovery of materials; waste-to-energy and bioenergy pathways; biomass utilization; critical minerals for renewable energy technologies; life cycle assessment and material flow analysis
System design and technological integration	Designing and integrating energy systems based on circular economy principles	Renewable energy systems design; modular and regenerative systems; system integration across energy and material infrastructures; technological innovation supporting circularity; design for durability, disassembly, and life cycle extension
Social, institutional, and governance dimensions	Enabling systemic change through policies, institutions, and social arrangements	Policy frameworks and regulatory instruments; governance and institutional coordination; stakeholder participation; cooperative and community-based energy models; social equity and energy justice considerations

). First, material and resource flows form a critical link. Circular approaches to critical minerals and renewable energy components emphasize recycling, reuse, and recovery to mitigate resource scarcity and environmental impacts [28]. For instance, recycling rare earths from wind turbines and electric vehicles is essential for reducing dependency on virgin extraction and secure supply chains [29].

Second, system design and technological integration show how circular economy principles can reshape the technical foundations of energy transitions. Strategies such as modular grid components, second-life battery applications, and renewable systems designed for disassembly exemplify the circular economy’s potential to enhance durability and reduce waste [15]. Initiatives such as district heating systems that recover waste heat, or modular solar panels that can be easily replaced and recycled, demonstrate how design innovations operationalize circularity in practice [30].

Third, social and equity considerations underscore the role of institutions and stakeholders in enabling change [31]. Some studies emphasize energy justice within low-carbon circular frameworks, highlighting equity in transition pathways [16,32]. Others work on cooperative governance in smart, circular energy systems, illustrating how circular-informed initiatives can deliver not only efficiency but also social inclusion [27]. Collectively, these contributions reveal the diversity of perspectives within the nexus and underscore the need for systematic mapping of the field.

A number of narrative reviews have attempted to explore the links between the circular economy and energy transitions. For example, Arruda et al. [23] reviewed different perspectives and concepts of the circular economy, while Leipold et al. [24] summarized the potentials and pitfalls of this research area and suggested three research needs. Other accounts reviewed stakeholder roles in circularity-driven transitions [31], the interplay of environmental and economic systems in the circular framework [33], social and justice dimensions in low-carbon circular transition frameworks [16,34], or cooperative governance in smart energy systems [17]. These contributions demonstrate the diversity of approaches to conceptualizing the nexus. However, narrative reviews are shaped by the authors’ disciplinary lenses and priorities. They often highlight selected themes while omitting others, resulting in fragmented pictures of the field. Their lack of systematic methodology also makes them difficult to reproduce, and their findings cannot easily be generalized beyond the scope of the chosen cases.

Systematic reviews and bibliometric studies employ rigorous and replicable methodologies, enabling transparent protocols, quantifiable performance measures, and visualized knowledge structures that reduce subjectivity. In the circular economy domain, Tu et al. [35] mapped urban circular transition pathways, while Alnajem et al. [36] and Teixeira [37] explored broader perspectives in the circular economy. However, these studies largely emphasize material flows, with limited attention to energy transition. Similarly, bibliometric analyses in renewable energy have traced the thematic evolution and intellectual structures of renewable energy research [6], yet they overlook how circular principles reconfigure energy systems. Thus, the circular economy–energy transition nexus is still under-researched, particularly from a systematic and integrative bibliometric perspective that simultaneously examines research performance, intellectual structure, and thematic evolution across disciplines.

This study intends to fill the gaps by capturing the intellectual structure and thematic clusters of scholarship at the circular economy–energy transition nexus. By combining performance analysis with science mapping, it addresses the limitations of narrative accounts and the narrow scope of existing systematic reviews. In doing so, it contributes to consolidating an emerging interdisciplinary research field and offers insights relevant for both academic and policy communities.

3. Methodology

The methodology of this study aligned with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines [38], which are widely recognized as a standard framework for transparent and reproducible reporting in bibliometric and systematic review research.

Scopus was selected as the sole database for this study, although both Scopus and Web of Science (WoS) are widely regarded as the leading databases for bibliometric research. Previous studies have demonstrated a high degree of overlap between Scopus and WoS, indicating that the inclusion of both databases is unlikely to substantially affect overall bibliometric patterns unless highly specialized bodies of literature are examined. Moreover, Scopus provides broader coverage of peer-reviewed publications than WoS, particularly in the social sciences and humanities, which makes it more suitable for addressing the objectives of this study.

The bibliometric data query was conducted on 26 August 2025. To capture the focused yet comprehensive body of literature directly relevant to the intersection of circular economy and energy infrastructures, three search criteria were applied:

• Keyword terms: The Boolean string TITLE-ABS-KEY ((“circular economy” OR “circularity” OR “closed-loop economy” OR “circular business”) AND (“energy transition” OR “energy transformation” OR “renewable energ*” OR “alternative energ*” OR “clean energ*” OR “green energ*” OR “sustainable energ*” OR “decarbonization” OR “low-carbon transition” OR “bioenerg*” OR “waste-to-energy”)) was developed for document searching. Structurally, the Boolean string consists of two keyword blocks. The first block includes terms related to the circular economy, while the second block contains terms associated with energy transition. The keywords were selected to balance inclusiveness, such as capturing diverse energy-related pathways including renewable energy and waste-to-energy, with precision, by focusing only on studies that explicitly frame these issues within the context of the circular economy. To further enhance search precision, synonyms and variant terms were incorporated using Boolean operators and wildcards. As a result, the Boolean string ensures that the dataset captures research explicitly linking the circular economy with energy transition, while minimizing the inclusion of unrelated publications.
• Document source: Only journal publications were included. Journals represent the most rigorous and peer-reviewed outlets for scientific knowledge, making them suitable for bibliometric mapping.
• Document type: The search was restricted to articles. This decision excludes reviews, editorials, and conference papers, focusing the dataset on original research contributions.

Following the query, an eligibility check was conducted to eliminate duplicate and irrelevant documents. Screening involved reading abstracts and checking for alignment with the circular economy–energy infrastructure nexus. After this process, a final dataset of 2977 articles was secured for bibliometric analysis. To ensure the accuracy and consistency of the subsequent bibliometric analysis, the dataset was cleaned and calibrated by eliminating inconsistent thesaurus terms and standardizing author names, journal titles, and keywords, through manual verification and consolidation of synonymous terms, spelling variants, and metadata inconsistencies.

Data analysis comprised two complementary approaches. First, performance analysis evaluates the influence and productivity of scholarly actors, including documents, authors, institutions, countries, and journals. Using Excel spreadsheets, various indicators were calculated: publication counts, number of citations, yearly publication trends, and distribution across sources and countries.

Second, science mapping reveals the intellectual structure and thematic dynamics of the field by examining relationships among bibliometric items. Four techniques were applied:

• Keyword co-occurrence analysis identifies major research themes by examining the frequency with which terms appear together.
• Document co-citation analysis reveals the intellectual foundations of the field by establishing a link between two papers when they are both cited by a third.
• Journal bibliographic coupling analysis explores intellectual linkages among research outlets by linking outlets that share common references.
• Country co-authorship analysis maps collaboration patterns by examining joint publications among nations, highlighting the geographical structure of the research network.

The results of bibliometric analysis were visualized using VOSviewer (version 1.6.20). Network maps were generated by minimizing the weighted sum of squared Euclidean distances between bibliometric items. In these maps, nodes represent biblio-graphic items (e.g., authors, keywords, documents), with node size reflecting the frequency or weight of the item. Lines depict relationships, with line weight indicating the strength of connections. The proximity between nodes illustrates their degree of relatedness. Colors indicate clusters, which are interpreted as thematic communities in co-occurrence maps, intellectual communities in co-citation and bibliographic coupling maps, and collaboration networks in co-authorship maps. Clusters were algorithmically generated using VOSviewer’s clustering algorithm, while their thematic interpretation and labeling were conducted through manual examination of dominant items within each cluster. Examples of these visual encodings are presented in the network maps in the Section 4.

4. Results

4.1. Overview

The publication trajectory of research on the circular economy–energy transition nexus has shown a remarkable accelerating upward trend over the past two decades (Figure 1). Following the first article in 2008, the field remained virtually non-existent until 2015, with only sporadic contributions. Between 2015 and 2018, however, publication activity began to increase modestly, growing from 8 articles in 2015 to 69 in 2018. A more pronounced acceleration is evident from 2019 onwards. The number of publications increased rapidly, reaching 114 in 2019 and further increasing more than sixfold to a partial-year record of 769 in 2025, representing the highest annual output to date.

The subject area distribution of the 2977 journal articles illustrates the interdisciplinary character of the field, as evidenced by the classification of articles across multiple subject areas and journals spanning environmental science, energy, engineering, and social sciences (

Table 2. Subject areas of articles on circular economy and energy transition.

Rank (nth)	Subject Area 1	Number of Articles 2
1	Environmental Science	1679
2	Energy	1305
3	Engineering	870
4	Social Sciences	517
5	Chemical Engineering	421
6	Business, Management and Accounting	298
7	Computer Science	277
8	Chemistry	265
9	Mathematics	227
10	Economics, Econometrics and Finance	226
11	Materials Science	209
12	Agricultural and Biological Sciences	203
13	Physics and Astronomy	121
14	Biochemistry, Genetics and Molecular Biology	97
15	Earth and Planetary Sciences	67
16	Decision Sciences	52
17	Multidisciplinary	50

¹ Only the subject areas that have at least 50 articles are shown. ² The total count is larger than the total number of articles because some articles belong to more than one subject area.

). Environmental science (1676 articles) emerges as the most represented subject area, reflecting the strong environmental orientation of the circular economy and energy transition. This dominance is likely reinforced by the field’s emphasis on evaluating environmental impacts and decarbonization outcomes, where widely used approaches such as life cycle assessment and sustainability frameworks align closely with environmental science research traditions and policy-relevant agendas. Energy contributes 1305 articles, underscoring the central role of energy systems in advancing sustainability transformations and linking circular strategies to low-carbon transitions. Engineering (870 articles) is the third largest contributor, reflecting the technical and design dimensions of the circular economy.

Beyond these leading categories, several social and applied sciences also make notable contributions. Social sciences (517 articles) highlight the socio-political transformations, such as governance, institutional frameworks, and equity dimensions, in the energy transition. Similarly, Business, Management, and Economics (298 articles) and Economics, Econometrics and Finance (226 articles) examine new business models, circular supply chains, and financing mechanisms to support sustainable transitions. Taken together, this distribution suggests that while engineering and other technical domains remain central, the field has increasingly engaged with social, governance, and market-oriented perspectives, reflecting a broadening from primarily technical approaches toward institutional and socio-economic dimensions of circular economy–energy transition research.

Smaller but important contributions come from Chemistry (265 articles), Materials Science (209 articles), and Agricultural and Biological Sciences (203 articles), which collectively examine the recovery and reuse of critical raw materials, biomass and bioenergy applications within circular systems. Even traditionally peripheral domains such as Decision Sciences (52 articles) and Multidisciplinary Studies (50 articles) contribute insights into optimization modeling, policy trade-offs, and integrated sustainability frameworks.

4.2. Keywords

The analysis of frequently occurring keywords offers a snapshot of the most prominent concepts used in publications at the nexus of the circular economy and energy transition. As shown in

Table 3. Most frequently occurring keywords on circular economy and energy transition.

Rank (nth)	Keyword 1	Occurrences
1	Circular Economy	1786
2	Renewable Energy	709
3	Sustainable Development	611
4	Sustainability	480
5	Recycling	460
6	Waste Management	426
7	Alternative Energy	339
8	Biomass	327
9	Anaerobic Digestion	295
10	Life Cycle	291
11	Environmental Impact	284
12	Biogas	280
13	Bioenergy	279
14	Energy	270
15	Life Cycle Assessment	255
16	Climate Change	254
17	Carbon Dioxide	253
18	Greenhouse Gases	210
19	Waste To Energy	202

¹ Only the keywords that occurred at least 200 times are shown.

, the most common term is “circular economy” (1786 occurrences), which is expected given the focus of the dataset. This high frequency demonstrates that the circular economy provides the conceptual and methodological foundation for research in this area [19,20].

The second most common group of keywords relates to energy themes, including renewable energy (709 occurrences), alternative energy (339 occurrences), energy (270 occurrences), bioenergy (279 occurrences), biogas (280 occurrences), biomass (327 occurrences), anaerobic digestion (295 occurrences), and waste-to-energy (202 occurrences). Together, these terms highlight the field’s strong emphasis on renewable and bio-based energy systems, reflecting the growing scholarly interest in linking circular economy principles with low-carbon energy.

Another important set of frequently used keywords relates to sustainability frameworks, including sustainable development (611 occurrences), sustainability (480 occurrences), life cycle (291 occurrences), and life cycle assessment (255 occurrences). The frequent use of these terms demonstrates the methodological orientation of the field toward life cycle thinking and holistic sustainability assessments, which help evaluate the environmental and social benefits of the circular economy–energy transition.

Finally, terms such as environmental impact (284 occurrences), climate change (254 occurrences), carbon dioxide (253 occurrences), and greenhouse gases (210 occurrences) underscore the alignment of the literature with global environmental and decarbonization agendas.

Beyond frequency, the co-occurrence network (Figure 2) illustrates how keywords interrelate. Using occurring at least 100 times as the threshold, 49 keywords that met the criteria were grouped into four clusters. They represent distinct but interconnected thematic domains.

The red cluster, “Renewable Energy and Sustainable Development,” is represented by keywords such as circular economy, renewable energy, alternative energy, sustainable energy, sustainability, sustainable development, and energy transition. This cluster underscores the pivotal role of the circular economy in linking renewable energy with broader energy transitions. Keywords in this group reflect scholarship on policy, governance, and economic drivers of sustainable transitions.

The green cluster, “Climate Impacts,” encompasses keywords such as climate change, greenhouse gases, carbon dioxide, carbon emission, carbon footprint, fossil fuels, decarbonization, life cycle, life cycle assessment, environmental impact, and environmental management. This cluster highlights a strong emphasis on evaluating the environmental consequences of circular economy–energy systems, particularly through life cycle methodologies. This cluster shows a close connection with the red cluster, as environmental assessments are often integrated into broader sustainability debates.

The blue cluster, “Bioenergy,” is represented by keywords such as bioenergy, anaerobic digestion, biogas, biofuel, methane, biomass, and food waste. This cluster emphasizes bioenergy production and biomass recovery, showcasing the circular economy’s role in transforming biomass and organic waste into renewable energy sources.

The yellow cluster, “Waste Management and Technology,” is represented by keywords such as waste management, municipal solid waste, recycling, waste incineration, waste disposal, waste-to-energy, and pyrolysis. This cluster highlights the technological and infrastructural pathways for operationalizing circular economy principles, with a focus on material recovery, recycling, and thermal conversion technologies.

The temporal co-occurrence map (Figure 3) provides valuable insights into the evolution of research priorities at the nexus of the circular economy and energy transition. The color coding, which assigns earlier-occurring keywords to purple and more recent ones to green and yellow, highlights how scholarly attention has evolved over time.

The earlier (purple) keywords indicate the concentration on practical solutions for waste and emissions management, with emphasis on biogas, waste incineration, and municipal solid wastes. Alongside these applied topics, there was attention to economics and gas emissions, suggesting that cost considerations and pollution control were integral from the outset.

As the field evolved, research interests gradually broadened, as reflected in the green and greenish keywords, shifting from specific technologies (e.g., biomass, biofuel, anaerobic digestion, and food waste) toward systemic environmental assessments (e.g., life cycle analysis, recycling, and waste management) and integration with global agendas (e.g., climate change, carbon dioxide, greenhouse gases, sustainable development, and renewable energy). These keywords reflect the connection between circular economy–energy transition studies and technological innovation with environmental evaluation and policy frameworks.

The recent (yellow) keywords reveal a stronger orientation toward systemic energy and climate strategies, represented by energy, energy transition, decarbonization, alternative energy, and sustainability. At the same time, technological innovation continues through advanced conversion methods such as pyrolysis.

4.3. Documents

The analysis of highly cited articles highlights the intellectual anchors of the field and illustrates how different research trajectories contribute to its rapid growth. A few thematic patterns emerge from the list of top-cited publications (

Table 4. Highly cited articles on circular economy and energy transition.

Rank (nth)	Document 1	Title	Year	Journal	Citations
1	Schroeder et al. [39]	The relevance of circular economy practices to the sustainable development goals	2019	Journal of Industrial Ecology	1156
2	Haas et al. [40]	How circular is the global economy?: An assessment of material flows, waste production, and recycling in the European union and the world in 2005	2015	Journal of Industrial Ecology	809
3	Malinauskaite et al. [41]	Municipal solid waste management and waste-to-energy in the context of a circular economy and energy recycling in Europe	2017	Energy	731
4	Martins et al. [42]	Analysis of fossil fuel energy consumption and environmental impacts in European countries	2019	Energies	713
5	Kätelhön et al. [43]	Climate change mitigation potential of carbon capture and utilization in the chemical industry	2019	Proceedings of the National Academy of Sciences of the United States of America	488
6	Norouzi et al. [44]	Circular economy in the building and construction sector: A scientific evolution analysis	2021	Journal of Building Engineering	349
7	Sharma et al. [45]	Waste-to-energy nexus for circular economy and environmental protection: Recent trends in hydrogen energy	2020	Science of the Total Environment	349
8	Stegmann et al. [46]	Plastic futures and their CO2 emissions	2022	Nature	341
9	Olabi et al. [47]	Assessment of the pre-combustion carbon capture contribution into sustainable development goals SDGs using novel indicators	2022	Renewable and Sustainable Energy Reviews	337
10	Awasthi et al. [48]	Refining biomass residues for sustainable energy and bio-products: An assessment of technology, its importance, and strategic applications in circular bio-economy	2020	Renewable and Sustainable Energy Reviews	302
11	Dahlbo et al. [49]	Recycling potential of post-consumer plastic packaging waste in Finland	2018	Waste Management	291
12	Kougias et al. [50]	Biogas and its opportunities—A review	2018	Frontiers of Environmental Science and Engineering	285
13	Zorpas [51]	Strategy development in the framework of waste management	2020	Science of the Total Environment	284
14	Gaustad et al. [52]	Circular economy strategies for mitigating critical material supply issues	2018	Resources, Conservation and Recycling	267
15	Gontard et al. [53]	A research challenge vision regarding management of agricultural waste in a circular bio-based economy	2018	Critical Reviews in Environmental Science and Technology	260
16	Marzorati et al. [54]	Green corrosion inhibitors from natural sources and biomass wastes	2019	Molecules	258
17	Bonsu [55]	Towards a circular and low-carbon economy: Insights from the transitioning to electric vehicles and net zero economy	2020	Journal of Cleaner Production	252
18	Pires & Martinho [56]	Waste hierarchy index for circular economy in waste management	2019	Waste Management	223

¹ Only the articles with more than 200 citations are shown.

).

The first pattern reveals three groups of seminal works that have anchored the field. One group provides conceptual and systemic frameworks linking the circular economy to sustainability transitions, e.g., Schroeder et al. [39] examining the relevance of the circular economy to the Sustainable Development Goals (SDGs), and Haas et al. [40] assessing global material flows and highlighting the limited circularity of current systems. A second group focuses on waste management and energy recovery, particularly in Europe, including studies on municipal solid waste and waste-to-energy systems [41], recycling of plastic packaging [49], waste management strategies [51], and a waste hierarchy index for circular economy applications [56]. The third group addresses climate change mitigation and industrial transformation, such as carbon capture and utilization in the chemical industry [43], projections of plastic-related CO₂ emissions [46], and assessments of carbon capture technologies in relation to SDGs [47].

The second pattern concerns the growing role of the bioeconomy and biomass valorization. Awasthi et al. [48] review biomass residues for sustainable energy and bio-products, Gontard et al. [53] highlight agricultural waste management in circular bio-economy contexts, and Marzorati et al. [54] explore green corrosion inhibitors derived from natural and biomass-based sources. Together with Kougias et al. [50] on biogas, and Sharma et al. [45] on hydrogen from waste-to-energy processes, these articles emphasize the role of biological resources in driving both circular and low-carbon transitions.

Third, several studies highlight sector-specific or cross-cutting transitions. Norouzi et al. [44] focus on the circular economy in the construction sector, Bonsu [55] addresses the transition to electric vehicles and low-carbon economies, and Martins et al. [42] analyze fossil fuel consumption in European countries. These works underscore the diversity of circular economy applications across different industrial and societal domains, highlighting the sectoral breadth of the literature.

On the other hand, the co-citation analysis identifying 54 documents reveals that scholarship on the circular economy and energy transition is intellectually structured into eight distinct clusters which can be further grouped into three broader domains (Figure 4).

At the center of the network, three clusters underscore the domain of conceptualization, governance, and policy frameworks.

The yellow cluster focuses on foundational conceptual debates and internationally recognized sustainability frameworks, drawing on core theoretical syntheses of circular economy [19,22,33] and global policy and development agendas [57,58]. The purple cluster highlights strategic visions and institutional policy frameworks [59,60,61], and alongside efforts to clarify and systematize key circular economy concepts [20]. The cyan cluster emphasizes analytical tools and emerging research frontiers, including studies on circularity measurement approaches [62], material flow analysis methodologies [63], and sectoral applications in agriculture [64] and energy storage technologies [65]. The brown cluster reflects European Union policy agendas, with cornerstone documents such as Closing the Loop [66] and the European Green Deal [25].

Two clusters at the eastern part of the network highlight the applications in materials, product design, and clean energy resource challenges. The green cluster centers on material efficiency and sustainable design strategies [15], and product life extension [67]. The orange cluster addresses resource challenges in renewable energy systems, including critical mineral demand [68,69], end-of-life [70], and e-waste flows [71].

The north-western domain consists of two clusters, highlighting the technological contributions of the circular economy to renewable energy generation, waste-to-energy, and bioenergy. The red cluster highlights thermal and biomass conversion technologies [72,73,74]. The blue cluster includes the analytic methods of wastewater [75] and foundational reviews of bioenergy and biogas [76,77].

4.4. Journals

The list of the most productive journals (

Table 5. Productive journals on circular economy and energy transition.

Rank (nth)	Journal 1	Articles
1	Sustainability (Switzerland)	190
2	Journal of Cleaner Production	173
3	Energies	153
4	Resources Conservation and Recycling	83
5	Journal of Environmental Management	62
6	Science of the Total Environment	58
7	Energy	52
8	Waste Management	45
9	Sustainable Production and Consumption	44
10–11	Biomass and Bioenergy	36
	Renewable Energy	36
12	Environmental Science and Pollution Research	34
13	International Journal of Hydrogen Energy	31
14–15	Chemical Engineering Journal	30
	Renewable and Sustainable Energy Reviews	30
16–17	Circular Economy and Sustainability	29
	Fuel	29
18	Applied Sciences (Switzerland)	27
19	Bioresource Technology	26
20–21	Journal of Industrial Ecology	25
	Resources Policy	25

¹ Only the journals that published at least 25 articles are shown.

) reveals the publication landscape of circular economy and energy transition research, highlighting the interdisciplinarity of the field and its strong presence in both sustainability-oriented and energy-focused outlets. The most productive journal is Sustainability (Switzerland) (190 articles), followed by the Journal of Cleaner Production (173 articles) and Energies (153 articles). These journals serve as the primary publication venues for the field, reflecting their broad scope and commitment to interdisciplinary sustainability transitions.

A second tier of journals emphasizes resource efficiency, environmental management, and engineering applications. These include Resources, Conservation and Recycling (83 articles), Journal of Environmental Management (62 articles), Science of the Total Environment (58 articles), Energy (52 articles), Waste Management (45 articles), and Sustainable Production and Consumption (44 articles).

A third group of journals reflects specialized domains and sectoral applications. Titles such as Biomass and Bioenergy (36 articles), Renewable Energy (36 articles), Chemical Engineering Journal (30 articles), Renewable and Sustainable Energy Reviews (30 articles), and Fuel (29 articles) indicate the centrality of bioenergy, renewable energy, and energy engineering within the circular economy literature.

Finally, many minor outlets demonstrate the breadth and diversification of the field. Journals such as Circular Economy and Sustainability (29 articles), Applied Sciences (Switzerland) (27 articles), Bioresource Technology (26 articles), Journal of Industrial Ecology (25 articles), and Resources Policy (25 articles) show that circular economy–energy transition scholarship is extending into policy, industrial ecology, and innovation studies.

The bibliographic coupling analysis of 47 journals (each with at least ten shared references) reveals a three-cluster structure within the publication landscape of circular economy and energy transition research (Figure 5). This structure highlights the interdisciplinary nature of the field, with clusters corresponding to technical and engineering journals, broad sustainability outlets, and applied environmental and management-focused journals. Overall, the results align closely with the journal frequency analysis.

The red cluster group’s journals are primarily concerned with engineering, energy systems, and resource recovery technologies. It includes journals such as Biomass and Bioenergy, Bioresource Technology, Fuel, Energy Conversion and Management, Environmental Science and Technology, and Renewable and Sustainable Energy Reviews. These journals emphasize the technological and experimental dimensions of the circular economy, focusing on biomass utilization, bioenergy, chemical engineering processes, and waste-to-energy conversion.

The blue cluster encompasses journals focused on environmental management, policy, and industrial ecology. These include Journal of Cleaner Production, Journal of Industrial Ecology, Waste Management, Resources, Conservation and Recycling, Journal of Environmental Management, and Science of the Total Environment. This cluster represents the applied and governance-oriented dimension of the field, highlighting how circular economy principles are operationalized through waste management strategies, material flow analysis, and policy.

The green cluster is dominated by journals with a broad sustainability and interdisciplinary orientation. Key titles include Sustainability (Switzerland), Energies, Applied Sciences (Switzerland), Renewable Energy, International Journal of Hydrogen Energy, Circular Economy and Sustainability, and Sustainable Energy Technologies and Assessments. These outlets provide platforms for research that integrates circular economy principles with renewable energy adoption and transitions, and systemic sustainability approaches. Positioned between the red and blue clusters in the network, the green cluster acts as a conceptual and integrative bridge, linking technical innovation with broader policy and sustainability debates.

4.5. Countries

The analysis of the most productive countries highlights the global geography of scholarship on the circular economy and energy transition, reflecting both research capacity and regional policy priorities. The results show that contributions are not evenly distributed but instead concentrated in a mix of advanced economies and rapidly developing countries that are simultaneously major energy consumers, industrial hubs, and sustainability policy leaders (Figure 6).

China is the most productive country with 399 articles, reflecting its strong research capacity and national emphasis on sustainability transitions. Next are European contributors, led by Italy (344 articles), Spain (262 articles), Germany (171 articles). Outside Europe, the United Kingdom (245 articles), United States (226 articles), and Australia (110) are three advanced economies standing out from the crowd. Among developing countries, India (281 articles) and Brazil (160 articles) are significant contributors. Asian economies, such as South Korea (96 articles), Malaysia (93 articles), Saudi Arabia (90 articles), Taiwan (71 articles), and Japan (52 articles), also show their growing interests in the circular economy and energy transition.

The co-authorship analysis of 45 countries with not less than 25 co-authored documents reveals the global collaboration structure in circular economy and energy transition research, organized into four clusters (Figure 7). The network map shows how these countries are grouped by strong co-publication ties, reflecting regional policy agendas, geographic proximity, and shared research priorities.

The red cluster is composed largely of European countries, including Germany, Italy, France, the Netherlands, the United Kingdom, and the Nordic countries. The dense interlinkages within this cluster illustrate the institutional support of the EU for circular economy-energy transition research.

The green cluster is the trans-Atlantic group, including the United States, Canada, Brazil, Mexico, Colombia, Portugal, and Spain who are central to this cluster. This cluster reflects the growing interest in biomass, bioenergy, and waste-to-resource strategies in the Pan-American Region [78], especially Latin America [79]. The links among Portugal, Spain, Brazil, Mexico, and Colombia indicate the common research interests between Europe and Latin America [80].

The blue cluster mainly includes emerging economies in Asia and the Middle East, including India, Saudi Arabia, Egypt, Vietnam, Iran, Turkey, and the Russian Federation. Led by India, this cluster reflects the growing role of emerging economies in adapting circular economy strategies for development [81].

Led by China, the yellow cluster includes many East and Southeast Asian countries, such as Japan, South Korea, Malaysia, Singapore, Taiwan, Japan, and South Korea. This cluster reflects the renewable energy innovation and resource efficiency in Asia [82].

5. Discussion

5.1. The Development of the Field

The rapid increase in publications on the circular economy and energy transition over the past decade illustrates how the field has developed from a marginal niche into a consolidated and fast-growing area of research. Before 2015, publication numbers were negligible, but since then output has risen sharply, surpassing 750 annual articles by 2025. This steep growth reflects not only expanding scholarly interest but also the growing policy salience of circular economy and decarbonization agendas, particularly after the European Union launched its Action Plan for the Circular Economy [66] and the Green Deal [25] marked important turning points for the field. These initiatives served as major catalysts for academic inquiry by shaping research funding priorities, incentivizing interdisciplinary projects, and directing scholarly attention toward themes such as resource efficiency, low-carbon transitions, and sustainable energy systems. At the global level, policy frameworks such as the United Nations Sustainable Development Goals provide a shared sustainability agenda that supports common framing across regions and may contribute to the international diffusion of circular economy and energy transition research themes [39].

The expansion of research has occurred alongside measurable shifts in real-world energy systems. Consistent with the growing prominence of energy transition- and renewable energy-related subjects in the bibliometric results, the share of renewable electricity generation at the global level has increased markedly in recent years, reaching about 32% of global electricity production in 2024. In the same year, clean power generation (renewables plus nuclear) surpassed 40% of global electricity, reflecting record growth in low-carbon generation [83]. Looking ahead, global renewable electricity expansion is projected to accelerate strongly over 2024–2030, driven primarily by solar PV and wind deployment [84]. Together, these parallel trends suggest that the growth of circular economy–energy transition research reflects not only policy salience but also accelerating structural change in global energy systems.

The expansion of the field is also closely tied to the emergence and maturation of specific subject areas. Environmental sciences and energy studies initially dominated, reflecting the technical and ecological roots of circular economy applications in resource efficiency, waste-to-energy, and renewable energy systems. This early emphasis aligns with foundational work in industrial ecology and circular economy conceptualization [19,20,22], and with early energy-related application domains, particularly anaerobic digestion and bioenergy systems [77], as well as life cycle assessment approaches for waste-to-energy technologies [73]. As the field matured, engineering (including chemical and materials engineering) expanded its presence, supporting research on biomass valorization, carbon capture, and waste recycling technologies [40,41]. More recently, social sciences, business, and management journals began contributing actively, indicating a broadening of the field toward governance, organizational strategies, and market-oriented approaches to circular economy transitions [21]. Thus, the upward trajectory in research output can be explained not only by sheer growth in numbers but by disciplinary diversification that continually opened new avenues of inquiry.

The journals in which these works are published reflect the inherently multidisciplinary composition of the field. Highly productive outlets such as Sustainability (Switzerland), Journal of Cleaner Production, and Energies highlight the central role of interdisciplinary platforms that integrate technological, environmental, and policy perspectives. At the same time, specialized journals such as Biomass and Bioenergy, Renewable Energy, and Waste Management underscore the strong technical and applied orientation of the field, particularly in energy recovery and resource valorization. Industrial ecology-oriented journals, including the Journal of Industrial Ecology and Resources, Conservation and Recycling, provide a conceptual and methodological anchor for assessing material flows and life cycle impacts.

5.2. The Evolution of Research Focuses

The thematic profile of circular economy–energy transition research can be organized around four interrelated themes which have adopted over time. The first theme, renewable energy and sustainable development, underscores the circular economy’s integration into wider sustainability discourses. Keywords such as circular economy, renewable energy, sustainable energy, alternative energy, sustainability, sustainable development, and energy transition highlight the field’s conceptual framing. This theme reflects scholarship on policy, governance, and economic instruments that facilitate circular economy principles in energy systems [6,31], with influential links to SDG-oriented circular economy framing [39] that help consolidate sustainability and governance framings that recur across this theme. The mean occurrence time analysis shows that some terms (e.g., economics) appear early, but more systemic concepts such as energy transition and decarbonization have become prominent only recently, reflecting growing recognition of the circular economy’s role in supporting global low-carbon agendas [3].

The second theme, climate impacts, demonstrates the methodological orientation toward life cycle thinking, enabling scholars to assess the environmental effectiveness of circular strategies [40], consistent with the established role of LCA in evaluating thermal waste-to-energy pathways [73]. Keywords such as climate change, greenhouse gases, carbon dioxide, carbon emission, life cycle, life cycle assessment, and environmental impact indicate that environmental science and industrial ecology have shaped the field, aligning with the global decarbonization agenda and international climate governance. Compared with earlier studies that framed the circular economy mainly in resource efficiency terms [19,20], this thematic stream shows how the field has matured into a central actor in climate mitigation debates.

The third theme, bioenergy, focuses on circular economy applications in converting organic waste and renewable resources into energy. Keywords such as bioenergy, anaerobic digestion, biogas, biomass, biofuel, and food waste highlight applied pathways of energy recovery and bioresource valorization [28]. Foundational contributions on anaerobic digestion and bioenergy potential have also shaped this stream [77]. This theme resonates with the engineering and applied energy sciences that have anchored circular economy research output from the start, reinforcing the findings on the development and composition of the field.

The fourth theme, waste management and technology, captures the operational and infrastructural dimension of circular economy–energy linkages. Keywords such as waste management, municipal solid waste, recycling, waste incineration, waste disposal, waste-to-energy, and pyrolysis emphasize the role of material recovery and thermal conversion technologies in implementing circular strategies [15]. This applied strand is consistent with earlier work on waste-to-energy technology pathways and assessments [72,73], including the role of waste-to-energy systems within circular economy contexts [41]. Some of these keywords (e.g., biogas, waste incineration, and municipal solid waste) represent the earliest research interests, reflecting the applied roots of the field. More recently, advanced technologies have gained prominence, illustrating how technological innovation continues to refresh this strand. In particular, pyrolysis has attracted attention for its potential to convert diverse waste streams into valuable energy carriers and materials, thereby enhancing resource recovery, reducing reliance on landfilling and incineration, and supporting low-carbon circular energy pathways.

5.3. Knowledge Structure of the Field

Seminal works in the circular economy–energy transition literature consist of a small set of highly cited papers that have defined its most visible directions. Policy- and governance-oriented studies are exemplified by [39], which linked circular economy practices to the SDGs and positioned circularity as a framework for global sustainability agendas. Methodological contributions, e.g., [40], quantified material flows and established benchmarks for assessing circularity, embedding industrial ecology and life cycle thinking into the field. Applied works on waste-to-energy [41] and on carbon capture [43] demonstrate how circular economy concepts have been operationalized through specific technologies, while climate-oriented studies, e.g., [47], highlight the alignment of circular economy strategies with decarbonization and carbon management efforts. Although these exemplars do not represent the full scope of the literature, they reveal the strands of research that have attracted the most recognition and shaped the field’s thematic profile.

The co-citation analysis, by contrast, uncovers the intellectual foundations that underpin these visible strands. The backbone of the field rests on conceptual syntheses, e.g., [19,20,22,33], complemented by strategic frameworks from institutes, e.g., [59,60], and by governmental directives and policy agendas, e.g., [25,61,66]. Building on this foundation, research in biomass, bioenergy, and waste-to-energy technologies provides the technological basis for circular economy applications in the energy sector [74]. Furthermore, studies on applications and design emphasize material efficiency, product strategies, and resource management for sustainable energy systems [15,68]. Beyond these internal sources, external references, e.g., [75], illustrate that the intellectual origins of the field extend beyond circular economy scholarship itself, drawing deeply on adjacent disciplines such as systems theory, sustainability transitions research, and behavioral and institutional economics, as well as on major policy agendas and standards that shape research practices.

5.4. Geography of the Research

The geography of circular economy–energy transition research is marked by uneven national productivity and distinctive international collaborations. China produces the largest share of publications, reflecting strong initiatives on the circular economy and massive investments in renewable energy infrastructure. For example, China’s carbon neutrality pledge (2060 target) and related transition strategies provide a relevant policy context for interpreting this high output, particularly given the accompanying scale-up of renewable energy infrastructure investment [10]. Several European countries, including the United Kingdom, Italy, Spain, Germany, and the Netherlands, also rank among the most productive. Specifically, the Green Deal and Circular Economy Action Plan provide an integrated policy framework that has supported research funding and cross-border collaboration, strengthening the region’s visibility in conceptual and policy-oriented scholarship [25,66]. The United States remains an important contributor but with less dominance compared to China or Europe. Recent policy shifts, particularly the Inflation Reduction Act of 2022, provide a relevant reference point for interpreting research momentum and research–policy alignment in the United States [9]. Emerging economies such as India and Brazil are increasingly visible, often emphasizing practical applications such as waste-to-energy and biomass utilization [11,79]. This visibility is consistent with policy priorities related to renewable energy and bioresource utilization, including India’s renewable energy targets [11] and Brazil’s emphasis on biomass-based pathways [2].

National variations in output mirror differences in political priorities, industrial capacities, and environmental pressures, consistent with the policy salience of circular economy and low-carbon transition agendas in major producing regions, particularly Europe’s Green Deal and Circular Economy Action Plan [25,66] and China’s carbon neutrality pathway framing [10]. They may also reflect structural factors such as unequal institutional research capacity, differential access to research funding and international collaboration networks, and language-related publication barriers that shape the visibility of scholarship in major bibliographic databases.

Collaboration patterns show how these productive countries connect within broader research networks. European nations form a cohesive network, supported by EU policy alignment and cross-border research funding [85]. China anchors an international network characterized by dense regional cooperation within Asia and selective partnerships with European countries. The United States actively coordinates across multiple regions, leading collaboration in the Pan-American sphere while also extending its influence into Europe [78]. These collaboration networks play an important role in shaping the dissemination of knowledge and the diffusion of innovation by facilitating the exchange of research agendas, methodological approaches, and technological solutions across national boundaries. At the same time, dense and recurrent collaborations may reinforce dominant research paradigms and accelerate innovation uptake within core networks, while peripheral regions risk slower diffusion and reduced visibility. Collaboration networks also appear in emerging regions, such as those linking Brazil with Latin American partners or Middle Eastern countries with African counterparts, where collaboration often responds to shared challenges and opportunities [79].

5.5. Emerging Research Gaps and Future Directions

Despite rapid growth, several gaps remain in circular economy–energy transition research. The first gap concerns the integration of technical innovations with systemic transition agendas. Earlier research emphasized waste-to-energy and bioenergy technologies, while recent studies highlight decarbonization, energy transition, and sustainability frameworks. Yet there is still limited work that explicitly connects these levels, for example, how advances such as pyrolysis or carbon capture feed into policy frameworks and long-term transition pathways. Future research should explicitly link circular economy-related energy technologies with governance, investment, and societal adoption in order to connect engineering innovations with long-term transition pathways, rather than treating applied and policy-oriented streams as parallel developments [6,45]. Methodologically, this can be strengthened through integrated socio-technical research designs that combine techno-economic assessment and life cycle assessment with policy analysis and stakeholder research, enabling explicit comparison of transition pathways across technologies and governance settings. Comparative multi-case studies across regions and sectors could also help connect technology performance with institutional and market conditions in real-world transition contexts. Related application areas, such as Renewable Energy Communities (RECs) [86] and Positive Energy Districts (PEDs) [87], translate circularity and decarbonization principles into place-based energy system design and community-level implementation.

The second gap relates to the assessment of environmental and social impacts across scales. Life cycle assessment and material flow analysis are well represented in the literature, e.g., [40], but their application is often confined to specific technologies or national contexts. There is a need for more cross-sectoral and comparative work that captures the cumulative effects of circular economy strategies on global climate mitigation, resource efficiency, and social well-being. Integrating LCA with broader sustainability metrics could help address concerns raised in co-citation foundations, where IPCC assessments and sustainability transitions research indicate the importance of systemic evaluation [3,7]. Future studies should adopt multi-method assessment frameworks that integrate life cycle assessment and material flow analysis with social impact assessment and energy justice perspectives, allowing environmental outcomes to be evaluated alongside distributional and procedural considerations. Cross-scale modeling approaches, for example, combining sector-level assessments with scenario analysis, could also improve the understanding of cumulative impacts and trade-offs across technologies and regions.

The third gap emerges from the geographical unevenness of research efforts and collaborations. Productivity remains concentrated in Europe and China, while many regions with pressing energy and waste challenges, such as Africa, Southeast Asia, and parts of Latin America, are underrepresented. Existing collaboration clusters largely mirror these patterns. The underrepresentation likely reflects uneven research capacity, limited access to research funding and international collaboration networks, and structural publication barriers, including language constraints and the indexing priorities of major bibliographic databases. As a result, global knowledge on the circular economy–energy transition nexus may privilege perspectives and policy agendas from well-resourced regions, while local insights and context-specific challenges in underrepresented regions receive less visibility. This imbalance affects global knowledge equity by narrowing the empirical base from which generalizations are made, and it may limit the transferability of dominant frameworks to diverse infrastructural and governance contexts. Future research should expand empirical focus to diverse socio-economic settings and examine how circular economy principles can be adapted to local infrastructures, governance arrangements, and cultural practices [88]. Such work would enrich the field’s applicability and broaden its intellectual foundations beyond the current centers of activity. Interdisciplinary approaches that combine local empirical fieldwork with harmonized bibliometric and comparative indicators could help improve the visibility of underrepresented contexts while maintaining analytical comparability. Methodological innovations, such as shared open datasets, standardized keyword thesauri, and multilingual search strategies across databases, could also help reduce publication and indexing biases, supporting more equitable global knowledge production and collaboration.

5.6. Implications for Theory, Management, and Policy

The findings of this bibliometric study carry important implications for theory, management, and policy. On the theoretical side, the results reinforce the idea that the circular economy is not a fixed or singular concept but a multi-layered framework that evolves through interaction with adjacent domains such as sustainability transitions, industrial ecology, and renewable energy. Conceptual works, e.g., [19,20], and systemic analyses, e.g., [39,40], have provided a common language that has enabled scholars from diverse fields to engage with the circular economy. The mapping of research themes and intellectual clusters shows that the circular economy has moved beyond being an abstract paradigm to function as a bridging concept, linking technological innovation, environmental assessment, and policy transitions. This confirms earlier claims that the circular economy is best understood as a cross-disciplinary framework capable of integrating heterogeneous disciplinary perspectives [22]. In particular, the circular economy and energy transition nexus is shaped by recurring linkages among policy frameworks, technology pathways, and assessment approaches, providing a clearer basis for future theory building that integrates these elements rather than treating them as separate strands.

From a managerial perspective, the results indicate that circular economy strategies can be operationalized through concrete decision areas across energy-related systems and supply chains, demonstrating their applied relevance in advancing energy transitions. There is a strong presence of research on waste-to-energy systems [55], specifically, bioenergy and biomass-based pathways [16], and carbon capture and utilization technologies [43], together with studies addressing material and resource constraints in low-carbon energy pathways [68]. These applied streams connect circular economy strategies to energy outcomes, including renewable energy uptake, energy recovery from waste streams, and decarbonization of energy supply chains. For managers and infrastructure operators, this implies prioritizing life cycle-oriented actions, including design for durability, repair and reuse, refurbishment, and end-of-life recovery, alongside performance evaluation that jointly considers resource circularity and decarbonization outcomes.

From a policymaking perspective, the results highlight the role of regulatory frameworks and public investment in shaping both research agendas and implementation pathways. The prominence of policy-driven themes and the centrality of European collaborations demonstrate that the circular economy has become a policy-relevant knowledge domain, directly informing EU initiatives such as the Green Deal [25]. This suggests that policies which simultaneously target circularity and low-carbon transitions, including standards for material recovery and recycling, incentives for circular design in renewable energy technologies, and support for system-level demonstrations, can help translate research insights into scalable energy transition outcomes. For practitioners such as engineers, policymakers, and businesses, this suggests that circular economy research offers not only incremental improvements (e.g., recycling rates, and biomass valorization) but also systemic strategies for resource efficiency, decarbonization, and sustainable development. Importantly, the geographic unevenness identified in this study also points to practical opportunities, especially that collaborations with emerging economies can help address pressing local challenges (e.g., waste management in India, or bioresource utilization in Brazil) while enriching global transitions [89].

6. Conclusions

This study examines 2977 journal articles on the nexus of the circular economy and energy transition. The results indicated that the field has expanded rapidly and become increasingly multidisciplinary. Four research themes, namely renewable energy and sustainable development, climate impacts and environmental assessment, bioenergy and biomass utilization, and waste management and technology, are identified. Earlier emphasis on waste-to-energy and emission reduction has gradually been complemented by bioenergy applications, environmental assessment frameworks, and most recently by systemic discussions of energy transition and decarbonization. The field is also structured by its seminal works and intellectual foundations. Highly cited documents illustrate several influential strands in the literature. These strands range from policy and conceptual frameworks to applied studies on waste management and carbon capture. Co-citation analysis further shows that these contributions draw on broader intellectual anchors. Knowledge dissemination occurs through three groups of journals. Geographically, Europe leads in conceptual and policy framing, China in industrial applications and scaling, and emerging economies such as India and Brazil in context-specific innovations. This multi-polar structure underpins the breadth and diversity of circular economy–energy scholarship today.

Looking forward, the field must further bridge conceptual models with applied technological studies, broaden its geographic inclusivity, and integrate frameworks that address trade-offs, rebound effects, and justice dimensions, such as life cycle sustainability assessment, socio-technical transition frameworks, and energy justice or just transition approaches. Doing so will strengthen theoretical foundations while advancing practical strategies for evaluating system-wide impacts and promoting sustainable and equitable energy transitions.

This study’s findings must be interpreted within several limitations. First, reliance on Scopus introduces potential biases, as regional or non-English publications may be underrepresented, reinforcing Anglo-European dominance. Triangulation with Web of Science or regional databases would enhance inclusivity, and future work could also compare database overlap and apply harmonized inclusion criteria across sources to reduce indexing-related bias. Second, results depend on keyword selection and search strategies. Despite being carefully designed, these may exclude relevant works using different terminology or include marginally related studies, so future studies could test alternative keyword combinations, incorporate controlled vocabulary and synonym expansion, and apply iterative refinement based on screening results. Third, bibliometric indicators such as co-citations, bibliographic coupling, and keyword frequencies are proxies that cannot fully capture conceptual depth or interpretive nuance. Highly cited works, for instance, may reflect policy salience rather than theoretical originality [90]. Future studies could further differentiate these dynamics by comparing citation patterns across policy-oriented and theory-oriented journals, or by combining citation metrics with qualitative content analysis to assess the nature of scholarly contributions. Similarly, co-authorship maps collaboration but not the quality of exchange. Future research could complement bibliometric analysis with qualitative approaches, such as in-depth literature reviews, expert interviews, or case-based analyses, to provide richer contextual and interpretive insights. Finally, temporal patterns inferred from keyword occurrences or citation averages are suggestive rather than precise, as scholarly fields evolve recursively rather than linearly [91]. Despite these constraints, this study offers a foundational mapping exercise that contributes a structured overview of the field’s intellectual foundations and thematic directions, offering a valuable point of departure for deeper conceptual and empirical inquiry, and providing insights that may inform future research design as well as policy discussions on integrating circular economy principles into energy transition strategies.