1. Introduction
Sustainable development is one of humanity’s most significant challenges in the 21st century. With the deepening influence of greenhouse gases and the increase in global energy consumption, the problem between the environment and energy consumption has aroused widespread concern and research. Environmental protection and energy-saving measures have become highly concerning global issues. In 2020, in response to international calls to reduce greenhouse gas emissions, the Chinese government proposed reaching the peak of carbon dioxide emissions by 2030 and striving to achieve carbon neutrality by 2060. The United States has pledged to return to the Paris Agreement in 2021, which also proposes new policies to reduce carbon emissions. At the same time, the European Union passed the European Union Act, which sets a goal of carbon neutrality by 2050.
With the gradual urbanization and modernization of countries worldwide, the construction industry has developed rapidly, and the energy demand and carbon emissions of building construction and use have shown a rising trend. The building sector is highly energy-consuming. In 2020, construction activities consumed 36% of global energy, and building carbon emissions accounted for 39% of global carbon emissions [
1]. At the same time, this field has excellent energy conservation and emission reduction potential, and the emission reduction cost is relatively low. It was found that by controlling building scale, selecting construction mode, reducing material supply-side emissions, and other measures, the embodied carbon emissions of China’s construction industry can be reduced by approximately 50% in 2060 compared with 2020 [
2,
3]. Therefore, building emission reduction is considered a critical link to achieving the long-term goal of controlling the global temperature rise within 2 °C, and this field is attracting more and more attention [
4,
5].
Currently, the literature on building carbon footprints published by Chinese and foreign scholars is abundant and complicated. It includes (1) Accounting for building carbon emissions, including the accounting of carbon emissions from building monomers at the micro level and the accounting of carbon emissions from buildings at the macro level. Various carbon emission accounting systems have been developed for single buildings at home and in foreign locations [
6,
7,
8]. At the micro level, the latest research focuses on the carbon emission accounting of different life-cycle stages of buildings [
9], building materials [
10], components [
11], and structural forms [
12]. Macro-level building carbon emissions accounting refers to the global, national, regional, provincial, and municipal scales of carbon emissions in the building sector. Its purpose is mainly to reflect regional building energy consumption and total carbon emissions and provide a basis for the government to formulate energy-saving and emission-reduction policies. Scholars at home and in foreign countries mainly use the input-output method (top-down) [
13] and the process analysis method (bottom-up) [
14] to measure embodied carbon emissions at the macro level. (2) The analysis model method of carbon emission influencing factors, such as IPAT model [
15], the exponential decomposition method [
16], the structural decomposition method, and other novel model methods [
17,
18]. (3) Research on influencing factors in building carbon emissions. The main factors that affect the carbon emission of buildings are energy structure, energy intensity, industry scale [
19], population [
20], income level [
21], residential building area, and urbanization level [
22].
The existing articles have various reviews of the research on building carbon emissions. Most review literature determined the research topics from a subjective point of view. These reviews often focus on household carbon emissions [
23], the neural network prediction method [
24], carbon reduction technology [
25], energy conservation policy [
26,
27], energy performances [
28], life cycle assessment [
29,
30], and the building act [
31]. For example, Pomponi et al. systematically reviewed the academic knowledge system of strategies to mitigate embodied carbon in the built environment [
32]. Chau et al. and Anand et al. have reviewed the application of LCA in the construction industry and pointed out the corresponding challenges and research directions [
33,
34]. Ma et al. carried out a systematic review of the implementation of the China Act on the Energy Efficiency of Civil Buildings (2008) [
31].
Due to its intuitive image and elimination of subjective screening errors, bibliometric analysis has been widely used in literature reviews in many research fields [
35]. Up until now, only a few bibliometric studies have focused on the carbon footprint of buildings. For example, Lu et al. systematically summarized green buildings’ strategy, technology, and mode of carbon emission [
36]. Luo et al. conducted a comprehensive and objective analysis of the research field of low-carbon buildings in 378 publications [
37]. Onat et al. analyzed the research frontier and characteristics of building a carbon footprint from the global supply chain perspective [
38]. Sun et al. summarized the construction sector’s carbon peak and neutrality through bibliometric analysis [
39]. We can find that the bibliometric analysis of the construction industry’s carbon footprint has also appeared.
In summary, the existing research still lacks the following: (1) Most of the existing carbon footprint bibliometry studies are based on the relevant literature on the global carbon footprint and do not focus on a specific industry to grasp the knowledge structure and development trend of its carbon emissions. (2) The literature review on building carbon emissions identifies the research topic mainly from a subjective point of view and tends to focus on methods and techniques. The review on building carbon emissions needs more quantitative analysis from an objective perspective. (3) Most previous studies used the Chinese CNKI and the international WoS databases to compare Chinese and foreign studies. Therefore, it is necessary to distinguish Chinese and foreign literature on building carbon emissions from a unified global literature perspective by using bibliometric analysis.
The aims of this study are as follows: (1) This paper identifies individuals and institutions conducting in-depth research on building carbon emissions in Chinese and foreign articles. It identifies subject categories related to the field. (2) This paper identifies the knowledge base and research focus of building carbon emissions in Chinese and foreign articles through various methods to ensure the reliability of the research results. (3) This paper compares the development process of topics that aroused scholars’ broad interest in Chinese and foreign articles.
This study is organized as follows:
Section 2 introduces the data sources and the methods adopted in the follow-up research.
Section 3 is a comparative analysis of the research situation on building carbon emissions, followed by keyword analysis and citation analysis.
Section 4 discusses the content that needs further research.
Section 5 summarizes the main conclusions. The research flowchart is shown in
Figure 1.
4. Discussion
By analyzing the research status of building carbon emissions in Chinese and foreign articles, we find that the current research results are very rich, and the research methods are diversified. However, there are still many research directions worth further exploration.
Clarify the system boundaries of building carbon emissions. Many articles use the life-cycle assessment method to estimate building carbon emissions [
52,
71,
72,
73,
74]. However, the system boundary of building carbon emissions is not clear, and there are differences in the definition of the building life cycle [
80,
81]. Different methods and models for analyzing building life cycle carbon emissions lead to different carbon emission results in the whole life cycle of buildings. It is urgent to clarify the boundaries of the life-cycle assessment system to conduct more in-depth research on building carbon emissions in the future. A comprehensive carbon factor database needs to be improved. Most studies use the inventory method to calculate building carbon emissions. Different calculation methods, years, and regions result in significant differences in calculation results. There still needs to be more research on the applicability of carbon emission accounting methods to different types of buildings. In the future, a building carbon emissions calculation based on a specific accounting method should be formed quickly to match building types with carbon emission accounting methods.
Green building, low-carbon building, and zero-carbon building assessment standards should be formulated globally. This includes expanding the scope of assessment from commercial buildings to rural residential buildings, so that all countries can measure and report their building carbon emissions in a consistent and comparable manner. In 2006, the UK announced the planning of ecological towns, requiring new buildings to be “zero-emission” by 2016 [
88]. The foreign green building evaluation system is relatively perfect; a relatively good evaluation system is the American LEED system (Leadership in Energy and Environmental Design) [
89], as is the German DGNB (Deutsche Gesellschaft für Nachhaltiges Bauen). However, the green building evaluation system needs to pay more attention to the building carbon emissions index [
90]. Compared to developed countries, studies in developing countries started relatively late in green, sustainable, and low-carbon buildings and have yet to establish widely recognized evaluation standards for low-carbon buildings. Developing countries need to increase policy support for low-carbon research, encourage enterprises to voluntarily comply with the requirements of low-carbon buildings through taxation and other means, strengthen the audit and supervision of the low-carbon status of buildings, and clarify the low-carbon standards. At the same time, researchers need to learn from historical development experience, promote the further development of low-carbon building research, improve the low-carbon building evaluation system, and enrich the research content.
The potential of individual energy conservation and emission reduction. The development of low-carbon buildings and life reflects residents’ pursuit of green life to some extent. However, the public’s understanding of low-carbon awareness is not comprehensive enough, resulting in insufficient trust in low-carbon buildings [
91]. Promoting of low-carbon buildings needs to be led by the government and considered from the two aspects of raising public awareness and establishing incentive mechanisms [
92]. To ensure end-user participation, the real estate housing market must introduce financial incentives to buy low-carbon buildings [
93]. The study found that the public is willing to learn more about renewable resource knowledge and hoped that the government could take corresponding measures to raise awareness of low-carbon buildings [
94]. Countries should take the government’s lead to publicize the advantages and benefits of low-carbon buildings, advocate a low-carbon lifestyle, enhance the awareness of low-carbon buildings, and thus increase the market demand for low-carbon buildings. With the shift of emission reduction policy to the consumer side, residents will play a crucial role in reducing carbon emissions.
Building carbon emissions in developing countries. Building carbon emissions is a comprehensive research field with strong practicability, but current research is mainly concentrated in China, the United States, the United Kingdom, Australia, and other major economies. With the improvement of economic development and urbanization, the energy consumption and carbon emissions of non-developed countries worldwide will experience unprecedented levels [
95]. China’s urbanization rate has risen from 38% in 2001 to 61% in 2019 [
96]. The consumption of large amounts of building materials during urbanization is an important factor driving China’s rapid surge in energy consumption and carbon emissions [
97]. India is the world’s fourth-largest emitter, and its energy demand increases with its economy and population [
98]. From 2000 to 2017, indirect emissions in India’s construction industry almost tripled. In 2019, the Indian construction sector accounted for 24% of the country’s carbon dioxide emissions. India’s urbanization level will reach 40% in the next decade, which will significantly drive the increase in building carbon emissions [
99]. The research on carbon emissions from the building industry in developing countries cannot be ignored [
95]. With the decline in the growth rate of the total building stock and the increase in the proportion of recycled building materials, the coordinated development of the construction sector and industry sectors will be more important [
2]. The synergy of the emission reduction effect between the construction and building materials manufacturing industries should be considered. Therefore, it is necessary to actively develop interdisciplinary research platforms, establish comprehensive research teams, strengthen openness and cooperation, strengthen connections with foreign universities, and promote transnational and inter-institutional collaborative research.
Carbon tax and carbon trading system. Scholars study allowance allocation from the perspective of efficiency [
100,
101] or fairness [
102,
103], trying to establish a reasonable and acceptable allocation scheme. The researchers proposed more than 20 allocation options, but none were widely accepted by climate conference [
104]. Moreover, in developing countries such as China, the allowance allocation is led by the government and currently only involves the power sector. Ref. [
105] points out that long-term use of the free method will reduce the efficiency of the emission trading system, and proposes a more effective carbon emission trading by auction. Allowance allocation through auction helps to improve the efficiency of emissions trading systems and maximize government revenue [
106]. Carbon markets may be the best way to balance development and emissions. With the development of carbon markets, future allowance allocations will be covered by other industries or sectors. Under the market mechanism, how to achieve a fair and effective allowance allocation is a subject worthy of research.
Low-carbon properties of building materials. With the proposal of the “double carbon” goal and the continuous popularization of the concept of green environmental protection, the development of the construction industry has gradually developed in the direction of sustainable development, and the construction side has increasingly recognized the application of green building materials. Energy conservation and emission reduction in the building industry are closely related to the development of building materials. The construction sector has the characteristics of “low carbon on the surface, high carbon hidden” [
107]. In the construction industry, the waste of resources and environmental pollution caused by traditional building materials have become urgent problems to be solved. Developing countries lag behind developed countries in the research of low-carbon building materials. However, developing countries are undergoing economic restructuring, and green and low-carbon building materials have enormous development potential. All parties should seize the opportunity, increase investment in the research and development of green and low-carbon building materials, strengthen the ability of technological innovation, improve production efficiency, and save resources by optimizing the production process.
5. Conclusions
This study compares the bibliometric differences between foreign and Chinese articles on building carbon emissions research. Two data sets of 4993 foreign and 1768 Chinese articles from 2008 to 2022 are analyzed using the Web of Science Core Collection database. Specifically, this paper compares aspects of publication object, journal, subject category, author, and institution. It discusses the differences in research trends and hotspots regarding keywords and citation analysis.
(1) The research on building carbon emissions shows a steady upward trend from 2008 to 2022. During the study period, the output and impact of foreign studies on building carbon emissions were generally higher than those of Chinese studies. Building carbon emissions is an interdisciplinary research topic involving the environment, energy, climate change, economics, green development, chemistry, and other natural sciences. The cooperation between institutions and organizations studying carbon emissions from the building sector is relatively weak. The influence of foreign articles on publications, journals, authors, and institutions is generally greater than that of Chinese articles. However, Chinese articles outperformed foreign articles for a few authors and institutions.
(2) Through keyword and citation network analysis, we found that the similarities and differences in conceptual and knowledge structure between foreign and Chinese articles are intertwined. For example, carbon footprint, energy, climate change, environmental impact, and greenhouse gas emissions are the common focus of both foreign and Chinese articles. However, foreign articles tend to focus on the impact of the whole life cycle of buildings on the environment. The low-carbon performance of cement, concrete, and other building materials is a new hot area of building carbon emissions in foreign articles. From the overall characteristics of the publication, the research on building carbon emissions in Chinese articles has prominent regional characteristics.
(3) In terms of the importance of the subject and maturity, the topic of ‘climate change’ in foreign articles is both important and highly developed. In contrast, the topic ‘climate change’ in Chinese publications is important but not well developed. The topics ‘carbon tax’ and ‘compressive strength’ are emerging in Chinese articles. Synergy between the construction industry and the steel industry is also an important research topic in Chinese articles. The topics of the core knowledge base of Chinese articles are more affluent than those of foreign articles. Overall, the thematic direction of Chinese articles is more divergent and lacks well-developed themes that greatly influence other research themes.
Finally, potential future research directions are proposed. Compared with the papers of Sun et al. [
39], this study combines VOSviewer, CiteSpace, HistCite, and the latest bibliophily R-package tools, with the help of new search strategies, to more accurately dig out academic hotspots and research trends. More importantly, this paper compares Chinese and foreign literature on building carbon emissions to reduce the subjectivity and one-sidedness of the research on building carbon emissions. Exploring the differences between foreign and Chinese articles on building carbon emissions can further improve the researchers’ ability to explore building carbon footprint research.