Establishment of an Environmental Impact Factor Database for Building Materials to Support Building Life Cycle Assessments in China

: The construction industry increasingly poses significant threats on the environment, high-lighting the importance of developing life cycle assessments (LCAs). Research on building LCA databases has been carried out in many countries. However, in China, the absence of public data for environmental impact assessments poses significant challenges for building life cycle assessments (LCA). Therefore, this study aims to facilitate the life cycle assessment of buildings in China by comparing and analyzing databases from South Korea and the European Union. The goal is to establish a unit-based environmental impact database for Chinese building materials. Three environmental impact factors of ten major building materials in these three databases were compared and a basis for the inter-application of the databases was established. Based on the combination of the analysis results, the supplementation of the environmental impact factor database of building materials in China was proposed. In addition, a case study using a quantity take-off (QTO) for an actual building in China was performed to review the plan’s applicability.


Introduction
Based on the statistics of the United Nations Environment Programme (UNEP), the construction industry has a substantial effect on the environment, accounting for ~40% of global energy consumption, 30% of raw material usage, 25% of solid waste, 25% of water resources, 12% of land resources, and 33% of greenhouse gas emissions [1].Nations are introducing various policies and developing advanced technologies to address this issue.To strengthen certification standards, developed countries, such as the United Kingdom (UK) and the United States (US), have gradually introduced building life cycle assessment (LCA) certification items into green building certification systems (e.g., BREEAM and LEED).In 2011, China developed the Standard for Sustainability Assessment of Building Project, a guideline for building an LCA [2].Similarly, in the Green Standard for Energy and Environmental Design (G-SEED) of South Korea, certification items for a building LCA were added to the certification system in 2016 [3].However, institutional support alone is insufficient for a building LCA.Based on ISO 14040, an LCA comprises four phases: goal and scope definition, life cycle inventory analysis, life cycle impact assessment, and interpretation [4].Because an inventory analysis requires the extensive support of various levels, regions, and raw data, high-quality data are important prerequisites for LCAs and the data quality directly affects the reliability and accuracy of LCA results [5].
Furthermore, the environmental effects of a building operation and those related to the production of materials used for construction must be considered during the evaluation of the environmental load of a building [6].Therefore, countries are establishing their building material LCA databases suited to their specific circumstances.LCA-related research began relatively late in China, and it is difficult to standardize regional material production processes and building structure types due to the country's vast territory [7].Furthermore, although many private research institutes are performing studies regarding the construction of their own databases to carry out LCAs, it is relatively challenging to build a national integrated environmental impact assessment database for building materials in a short period of time because of the differences in the methods that are used for the collection of inventory data [8].In China, due to a lack of established databases, there is significant reliance on foreign databases.However, differences in regional characteristics within China and variations in the processes of material production create distinctions in the databases of different countries.Therefore, when utilizing foreign databases, there is a risk of introducing errors in the assessment results for the entire lifecycle of buildings [9].Therefore, the establishment of a database considering the environmental impact of building materials within China is absolutely necessary.Hence, this study aims to build a unit-based environmental impact database for Chinese building materials by conducting a comparative analysis of databases from South Korea and the European Union.The objective is to support the lifecycle assessment of buildings in China.

Methodology and Flow of Research
To develop a building materials LCI database we analyzed building LCA systems and material databases for each country.The Chinese Life Cycle Database (CLCD), a Korean database, and the European Life Cycle Database (ELCD) were selected as target databases.
To construct an environmental impact factor database that can be used in China, ten major building materials were selected and analyzed based on prior research results.The analysis scope included three major environmental impact categories.Similarities and differences were identified based on the comparative analysis of environmental impact factor databases for selected building materials and the applicability of each database was analyzed.Based on the analysis results, this study proposes a plan to construct an environmental impact factor database for building materials that can be used in China.In addition, a case study using quantity take-off (QTO) for a building in China was performed to review the plan's applicability.The framework of this study is presented in Figure 1.

Literature Review
An LCA is used to quantify the amount of energy and materials consumed and emitted throughout the life cycle of products and services to evaluate their effects on the environment.An LCA is an important environmental management tool, which is included in

Literature Review
An LCA is used to quantify the amount of energy and materials consumed and emitted throughout the life cycle of products and services to evaluate their effects on the environment.An LCA is an important environmental management tool, which is included in the ISO 14000 international environmental standards and provides the basis for the methods of other environmental management tools belonging to the same standard.A building LCA is an environmental impact assessment based on the amount of material input or energy consumption throughout a building's life cycle, that is, the production of building materials, transportation to the construction site and construction, building use and maintenance, and disposal and recycling.
The importance of a building LCA is growing both in South Korea and overseas, and related research has been carried out in numerous countries.Table 1 shows the environmental impact assessment systems for buildings in China, South Korea, the UK, and the US.Because each country provides guidelines for performing a building LCA using a building materials LCI database, it is necessary to continuously supplement the building materials databases.The LCI databases are used as basic data for conducting LCAs of products.Such data include the quantities of inputs and outputs into a product system during the collection of raw materials needed for production, transportation and distribution, use, and disposal per functional unit of the product.
Countries and research institutes have constructed LCA databases to support the LCA process.Table 2 shows the results of the reviews of four databases, that is, the CLCD, a Korean database, ELCD, and Ecoinvent (Switzerland).The CLCD is not a national database; it was built by the research center at the Sichuan University College of Architecture and Environment.The only currently published LCA database in China contains data of a total of 575 industries including energy and resources, building materials, industrial products, transportation and logistics, chemicals, and basic raw materials.Based on the review, although the types and specifications for structural materials, such as rebars and steel frames, in the CLCD are relatively sufficient, the specifications for other building materials, such as cement, gypsum board, and insulation, are either insufficient or missing.Therefore, data must be supplemented.
Takano et al., 2014 conducted a mutual environmental performance comparison by selecting five construction materials and applying their data to two different buildings, revealing differences in the data.However, the limitations include the use of a small number of construction materials and the failure to present a database [11].
Lasvaux et al., 2015 utilized a database constructed in France to compare and analyze European data, but the limitations include presenting simple comparative results and a lack of a readily applicable database [12].
A. Martínez-Rocamora et al., 2016 proposed criteria for selecting data to improve the opacity and inconsistency when applying LCA databases to buildings.However, similar to other studies, the limitation lies in the small number of data and the absence of a database applicable to entire buildings [13].
Mohebbi G. et al., 2021 presented criteria for calculating embodied carbon in building environmental impact assessments in the UK.Nevertheless, the limitation is that it does not cover data for the entire building life cycle, focusing instead on major construction materials [14].
Therefore, in this study, we aim to derive a database suitable for application in Chinese buildings by conducting a comprehensive environmental performance assessment of major construction materials throughout the entire life cycle in China, Republic of Korea, and Europe.

2016
A. Martínez-Rocamora et al. [13] Establishing criteria for selecting LCA databases when there are mismatches in the conditions applied to buildings.
Although criteria for selecting building LCA databases have been provided, the actual construction of a database that meets these criteria has not been proposed.

2021
Mohebbi, G et al. [14] Establishing criteria for carbon input calculations within the UK.
While data for calculating carbon input in the UK has been provided, there is a limitation in not assessing materials used in the "whole process" of building construction.

Derivation of Building Materials for Environmental Impact Analysis
To analyze the building material factor database of each country, target building materials were selected based on a literature review from the perspective of building LCA.Table 4 presents the findings of previous studies [3].Lim derived six major building materials for general buildings including concrete, aggregate, brick, rebar, cement, and stone, which account for 95% of the cumulative weight, according to the ISO 14040s cut-off criteria for LCA [4,15].Roh selected six major building materials, including concrete, rebar, steel frame, glass, cement, and insulation, which account for 95% of the total greenhouse gas emissions [16].Roh also selected six major building materials, including concrete, rebar, insulation, concrete brick, glass, and gypsum board, which account for over 95% of the six major environmental impact characterization values, using case studies [17].Hence, based on the literature review, the ten building materials included in prior research (concrete, cement, rebar, aggregate, brick, stone, steel frame, glass, insulation, and gypsum board) were selected as the major building materials to be investigated in this study.

Setting the Scope of the Environmental Impact Assessment for Building Materials
Under G-SEED in South Korea, global warming (greenhouse gas emissions) and at least two other environmental impact categories must be included as evaluation items for building LCA.Although the LCA guideline in China lists 12 environmental impact categories, the regulations on the environmental impact categories to be included in actual LCAs are unclear.Therefore, three environmental impact categories defined by G-SEED were analyzed in this study: global warming potential (GWP), acidification potential (AP), and eutrophication potential (EP) [18].

Comparative Analysis of Each Building Material's Environmental Impact 4.3.1. Selection of a Target Building Material Factor Database for Each Country
For each of the selected target building materials, target LCI databases with similar characteristics were selected, as shown in Table 5.The Korean National LCI database was preferentially applied [19].For building materials not included in the National LCI database, the National Environmental Information Database and National LCI Database for Construction Materials were used [20].Concerning concrete, LCI databases for 30 and 50 MPa, 21 and 24 MPa, and 20/25 MPa concrete were built in China, South Korea, and the EU.Therefore, concrete with similar strengths of 30, 24, and 20/25 MPa was selected for the analysis in this study.Because there are no separate data for gypsum board in the Chinese database, natural gypsum was selected as the analysis target, whereas gypsum board was selected for South Korea and the EU [21].The Chinese database does not contain insulation data; therefore, expanded polystyrene, which is included in both the South Korean and EU databases, was selected for the comparative analysis.Regarding bricks, aerated concrete blocks were selected among aerated concrete and lightweight concrete in the EU in this study due to their similar characteristics with concrete bricks in China.Regarding stone, shale is the only building stone in the CLCD, marble and granite are the building stones in the Korean database, and building stones are not included in the ELCD; thus, there were no stones with similar characteristics.However, the aim of this study was to further establish environmental impact factors in China.Therefore, shale from the Chinese database and granite from the Korean database were selected for the analysis [22,23].

Analysis Results of the Environmental Impact Factor Databases for Each Building Material
Given the absence of stones with similar characteristics among the countries, stones were excluded from the comparative analysis of environmental impact factors for major building materials.As shown in Figure 2, the Chinese database was used as the 100% baseline in the analysis results of major building materials.The detailed analysis is described below [24].
Buildings 2024, 14, x FOR PEER REVIEW 8 of 16 Korea and twice as large as those of the EU.Overall, the environmental impact factors for brick in China were more similar to those in the EU.The databases of each country did not contain stones with similar characteristics.Therefore, a comparative analysis of shale in the Chinese database and granite in the South Korean database was conducted in this study.The Republic of Korea's GWP was ~45 times that of China, whereas the differences of the AP and EP between the two countries were relatively small.The AP and EP of South Korea were twice the values of China.
Regarding the overall analysis results (excluding insulation because it was not included in the Chinese database), the environmental impact factors of the GWP and AP of each building material in China, the Republic of Korea, and the EU showed similar trends, with ~1-5-fold differences.Among these factors, the GWP of concrete, cement, glass, and sand and AP of concrete, cement, and gypsum board were very similar, differing by a factor of <1.5.China's and South Korea's EP was relatively similar, with a ~1-3-fold difference, excluding glass for which the difference was 30-fold.
These results suggest that a similar database of another country can be applied to supplement data when a building material database is insufficient or unavailable during building LCA.However, for factors with large differences, such as factors of the raw material input and energy resources consumed in the material production process, additional comparative analyses are needed.The environmental impact factors of the GWP, AP, and EP for concrete in China were similar to those of South Korea and the EU, with a less than 1.5-fold difference.In particular, the GWP of China and the EU differed by a factor of 1.1, making it the most similar environmental impact factor.As shown in Figures 3 and 4, Similar to concrete, the GWP, AP, and EP of cement in China and the Republic of Korea differed by a factor of up to 1.5.The EU's environmental impact factors were overall higher than those of China and the GWP, AP, and EP greatly differed (by up to a factor of ~2).Thus, the environmental impact factors obtained for cement in China were similar to those of South Korea.In contrast to concrete, for which similar trends were observed, the environmental impact factors of rebar in China were higher than those in South Korea and the EU.China's values for the three major environmental impact factors were 1.9 to 5.3 times greater than those of the Republic of Korea and 1.8 to 3.1 times greater than those of the EU.Overall, China's environmental impact factors for rebar were similar to those of the EU.The Republic of Korea's GWP for steel frame was ~1.8 times smaller than that of China, whereas the AP and EP were 3.4 and 1.6 times larger than those of China.The EU's GWP, AP, and EP were 1.4, 1.8, and 3 times smaller than those of China, respectively.Thus, the EU database with a smaller difference in the environmental impact of the GWP has overall more similar environmental impact factors.The environmental impact factors of glass showed similar trends to those of rebar.China's values were larger than those of South Korea and the EU.China's GWP was similar to that of the Republic of Korea and the EU, with a difference of a factor of 1.37, whereas the difference in the AP was relatively large, with a factor of ~3-5, and the EP was the factor with the largest difference (5-to 30-fold).Because natural gypsum, a material in the Chinese database, is an unprocessed raw material, its environmental impact factors were smaller than those of gypsum board in the Republic of Korea and the EU.The South Korean value was 1.8 to 4.4 times and 1.2 to 6.8 times greater than that of China and the EU, respectively.The EU's environmental impact of the AP was similar to that of China, with a 1.2-fold difference, whereas the environmental impact of the GWP was the most different (6.8-fold).Accordingly, the South Korean database with a smaller difference in the environmental impact of the GWP has overall more similar environmental impact factors.The results for aggregate were similar to those obtained for cement.The GWP, AP, and EP of China and South Korea differed by up to a factor of ~1.5, whereas the GWP, AP, and EP of China and the EU showed relatively large differences of up to a factor of ~2.Overall, the environmental impact factors for aggregate in China were similar to those in the Republic of Korea.Because insulation data are not included in the Chinese database, a comparative analysis was performed between the environmental impact factors of South Korea and the EU.The three major environmental impact factors for insulation obtained for the Republic of Korea and the EU were similar, with a 1.6-2.2-folddifference.Regarding brick, larger values were determined for China than for South Korea and the EU.China's GWP, AP, and EP were ~5 to 12 times larger than those of South Korea and twice as large as those of the EU.Overall, the environmental impact factors for brick in China were more similar to those in the EU.The databases of each country did not contain stones with similar characteristics.Therefore, a comparative analysis of shale in the Chinese database and granite in the South Korean database was conducted in this study.The Republic of Korea's GWP was ~45 times that of China, whereas the differences of the AP and EP between the two countries were relatively small.The AP and EP of South Korea were twice the values of China.Korea and twice as large as those of the EU.Overall, the environmental impact factors for brick in China were more similar to those in the EU.The databases of each country did not contain stones with similar characteristics.Therefore, a comparative analysis of shale in the Chinese database and granite in the South Korean database was conducted in this study.The Republic of Korea's GWP was ~45 times that of China, whereas the differences of the AP and EP between the two countries were relatively small.The AP and EP of South Korea were twice the values of China.
Regarding the overall analysis results (excluding insulation because it was not included in the Chinese database), the environmental impact factors of the GWP and AP of each building material in China, the Republic of Korea, and the EU showed similar trends, with ~1-5-fold differences.Among these factors, the GWP of concrete, cement, glass, and sand and AP of concrete, cement, and gypsum board were very similar, differing by a factor of <1.5.China's and South Korea's EP was relatively similar, with a ~1-3-fold difference, excluding glass for which the difference was 30-fold.
These results suggest that a similar database of another country can be applied to supplement data when a building material database is insufficient or unavailable during building LCA.However, for factors with large differences, such as factors of the raw material input and energy resources consumed in the material production process, additional comparative analyses are needed.

Setting Building Materials and Environmental Impact Categories
In this chapter, based on the analyzed results from the previous section, we aim to selectively identify construction materials suitable for application in China, categorizing them by country.In the previous section, we conducted a comparative analysis of the Global Warming Potential (GWP), Acidification Potential (AP), and Eutrophication Potential (EP) of construction materials in China, Korea, and Europe.The selection criteria were established by comparing and analyzing the environmental impact values of data from China, the Republic of Korea, and Europe.In cases where the environmental impact values were similar, we validated the selection for Chinese materials.In situations where there was no available Chinese database, we opted for a database similar to China's environmental conditions.For cases with significantly different environmental impact results, we considered the unique characteristics of China's production processes and tailored the Chinese database accordingly.
The ten building materials analyzed above (concrete, cement, rebar, steel frame, glass, insulation, gypsum board, aggregate, brick, and stone) were selected as the target building materials.The database was designed and constructed to support the evaluation of three major environmental impact categories (global warming, acidification, and eutrophication) and each environmental impact category was evaluated using equivalents, as shown in Table 6.

Proposal of an Environmental Impact Factor Database for Building Materials
Based on the analysis results, Table 7 presents environmental impact factor databases for major building materials that can be used in China.
To build an environmental impact factor database for building materials that can be used in China, ten building materials (concrete, cement, rebar, steel frame, glass, insulation, gypsum board, aggregate, brick, and stone) were selected as the target building materials.The database was designed to support the evaluation of three major environmental impact categories (global warming, acidification, and eutrophication).Based on the comparative analysis of each country's environmental impact factor database, an environmental impact factor database was built for a total of 54 building materials.For 37, 14, and 3 materials, the CLCD, South Korean database, and ELCD were used, respectively.Data- Regarding the overall analysis results (excluding insulation because it was not included in the Chinese database), the environmental impact factors of the GWP and AP of each building material in China, the Republic of Korea, and the EU showed similar trends, with ~1-5-fold differences.Among these factors, the GWP of concrete, cement, glass, and sand and AP of concrete, cement, and gypsum board were very similar, differing by a factor of <1.5.China's and South Korea's EP was relatively similar, with a ~1-3-fold difference, excluding glass for which the difference was 30-fold.
These results suggest that a similar database of another country can be applied to supplement data when a building material database is insufficient or unavailable during building LCA.However, for factors with large differences, such as factors of the raw material input and energy resources consumed in the material production process, additional comparative analyses are needed.

Setting Building Materials and Environmental Impact Categories
In this chapter, based on the analyzed results from the previous section, we aim to selectively identify construction materials suitable for application in China, categorizing them by country.In the previous section, we conducted a comparative analysis of the Global Warming Potential (GWP), Acidification Potential (AP), and Eutrophication Potential (EP) of construction materials in China, Korea, and Europe.The selection criteria were established by comparing and analyzing the environmental impact values of data from China, the Republic of Korea, and Europe.In cases where the environmental impact values were similar, we validated the selection for Chinese materials.In situations where there was no available Chinese database, we opted for a database similar to China's environmental conditions.For cases with significantly different environmental impact results, we considered the unique characteristics of China's production processes and tailored the Chinese database accordingly.
The ten building materials analyzed above (concrete, cement, rebar, steel frame, glass, insulation, gypsum board, aggregate, brick, and stone) were selected as the target building materials.The database was designed and constructed to support the evaluation of three major environmental impact categories (global warming, acidification, and eutrophication) and each environmental impact category was evaluated using equivalents, as shown in Table 6.

Proposal of an Environmental Impact Factor Database for Building Materials
Based on the analysis results, Table 7 presents environmental impact factor databases for major building materials that can be used in China.To build an environmental impact factor database for building materials that can be used in China, ten building materials (concrete, cement, rebar, steel frame, glass, insulation, gypsum board, aggregate, brick, and stone) were selected as the target building materials.The database was designed to support the evaluation of three major environmental impact categories (global warming, acidification, and eutrophication).Based on the comparative analysis of each country's environmental impact factor database, an environmental impact factor database was built for a total of 54 building materials.For 37, 14, and 3 materials, the CLCD, South Korean database, and ELCD were used, respectively.Databases with environmental impact factors more similar to those of China were preferentially applied to the construction of the database.If the environmental impact factors significantly differed, the South Korean database with smaller regional differences with China was applied.However, an additional comparative analysis of the basic materials and energy consumed in the production process of the material should be carried out in case of significant differences.

Case Study 6.1. Overview
This chapter aims to validate the credibility of the newly constructed primary building material environmental impact unit-based database through the research.In the previous chapter, applicable databases for key building materials such as concrete and steel within China were established through data analysis.The newly constructed major building material database was applied to actual buildings to assess the environmental impacts of global warming, acidification, and eutrophication during the production phase of construction materials.The assessment results were compared with existing environmental impact unit-based databases (China CLCD, Korean database, European Union ELCD), and the analysis focused on evaluating the environmental impact results based on national environmental impact units.

Case Study Target and Method
The target of the case study was a reinforced concrete dormitory building in the Henan Province, China.The environmental impact factors of each database were applied to the input quantities of the major building materials calculated using the QTO based on which the environmental impacts of the major building materials were assessed.The environmental impact assessment results of the target building's building materials were derived at the building level and used to validate the reliability of the constructed database.
The major building materials accounting for >99% of the cumulative weight used in the target building are concrete, aggregate, brick, cement, rebar, and tile.Because tile is not included in any of the databases, it was excluded from the assessment.Because the insulation must be evaluated according to regulations, an additional environmental impact assessment was conducted for this material.
The materials used in the target building were classified based on the major building materials in Table 8 and matched with each LCI database for major building materials.For concrete, each LCI database was matched according to the strength.Because none of the LCI databases contained data for concrete panels, the same evaluation as that used for concrete blocks was performed.Aerated concrete block was utilized for the database constructed in this study and the ELCD and concrete block was used for the CLCD.The material specifications for cement, rebar, and insulation of the different databases differ.Therefore, the LCI database values for Portland cement, rebar, glass wool, and expanded polystyrene were applied in this study.Although China's database does not contain insulation, it was assumed that the environmental impact values of insulation would not affect the overall environmental impact assessment of the building materials because very little insulation was used according to the QTO.

Case Study Results
Table 9 shows the results of the assessment of the environmental impact of each building material on global warming, acidification, and eutrophication at the building level for the building material production stage using the environmental impact factor database for building materials constructed in this study as well as existing databases.The results obtained from each database are compared in Figure 5.

Discussion
In this study, an environmental impact factor database for building materials was established for the purpose of supporting the building life cycle assessment in China.This study is expected to provide the basis of establishing a standardized environmental emission factor database at the national level and help to prepare for institutionalization of a building LCA.
In this study, ten main building materials (concrete, reinforcing steel, cement, aggregate, bricks, stone, steel frame, glass, insulation material, gypsum board) were identified, and three environmental impact categories (global warming potential, acidification potential, eutrophication potential) were selected for the analysis scope.Additionally, a new database was constructed in this study using data from Korea, Europe, and China, and its applicability in China was evaluated.The results showed differences of 6%, 13%, and 14% in global warming potential (GWP), acidification potential (AP), and eutrophication potential (EP), respectively.While the GWP demonstrated immediate applicability, the AP and EP exhibited relatively higher error rates, likely due to the lack of Chinese data for these impact categories.Therefore, it is suggested that further research is needed for the development of a Chinese database.
However, depending on the environment of each country and region, there may be differences in the input ratio and transport distance of the raw materials of each building material which consequently causes difference in the life cycle environmental impact of each building material.Accordingly, the information on raw materials which affects the environmental impact should be arranged and considered when selecting the most appropriate DB.Moreover, in order to institutionalize and operate a building LCA at the national level, research to standardize the process of a building LCA using the DB as well as DB development should be carried out in further studies.

Conclusions
In this study, a comparative analysis of environmental impact factor databases for major building materials in China, the Republic of Korea, and the EU was performed and a plan for the construction of a Chinese database was proposed.The following conclusions can be drawn.
Based on the literature review, ten building materials (concrete, rebar, cement, aggregate, brick, stone, steel frame, glass, insulation, gypsum board) were selected as the major Based on the assessment of three major environmental impact factors, the CLCD shows the largest environmental impact values, followed by the new database, ELCD, and South Korean database.The CLCD yields the largest overall assessment results because the environmental impact factors of rebar and brick are relatively large, whereas the South Korean database yields the smallest overall assessment result because the environmental impact factors of rebar and brick are small.
To determine the reliability of the new database, the AP and EP were considered in addition to the GWP in this study and the evaluation results were compared with those obtained with the existing Chinese database.For the GWP, the error rate between the evaluation results using the new database and that using the CLCD was 6%.For the AP, the error rate between the evaluation result using the new database and that using CLCD was 13%.For the EP, the error rate between the evaluation result using the new database and that using CLCD was 14%.The average error rate was 11%; therefore, the results of the three major environmental impact assessments were determined to be similar, which was attributed to the lower proportion of bricks.Although the bricks used in the target building are lightweight concrete blocks, concrete blocks were used when matching the QTO with the LCI database because the CLCD did not contain lightweight concrete blocks.Because the CLCD yielded the highest environmental impact factors for concrete blocks among the three countries, the assessment values are the largest.The new database was supplemented using lightweight concrete blocks from the ELCD, which yielded a high match rate; therefore, the accuracy improved, although the environmental impact assessment values were smaller than those of China.

Discussion
In this study, an environmental impact factor database for building materials was established for the purpose of supporting the building life cycle assessment in China.This study is expected to provide the basis of establishing a standardized environmental emission factor database at the national level and help to prepare for institutionalization of a building LCA.
In this study, ten main building materials (concrete, reinforcing steel, cement, aggregate, bricks, stone, steel frame, glass, insulation material, gypsum board) were identified, and three environmental impact categories (global warming potential, acidification potential, eutrophication potential) were selected for the analysis scope.Additionally, a new database was constructed in this study using data from Korea, Europe, and China, and its applicability in China was evaluated.The results showed differences of 6%, 13%, and 14% in global warming potential (GWP), acidification potential (AP), and eutrophication potential (EP), respectively.While the GWP demonstrated immediate applicability, the AP and EP exhibited relatively higher error rates, likely due to the lack of Chinese data for these impact categories.Therefore, it is suggested that further research is needed for the development of a Chinese database.
However, depending on the environment of each country and region, there may be differences in the input ratio and transport distance of the raw materials of each building material which consequently causes difference in the life cycle environmental impact of each building material.Accordingly, the information on raw materials which affects the environmental impact should be arranged and considered when selecting the most appropriate DB.Moreover, in order to institutionalize and operate a building LCA at the national level, research to standardize the process of a building LCA using the DB as well as DB development should be carried out in further studies.

Conclusions
In this study, a comparative analysis of environmental impact factor databases for major building materials in China, the Republic of Korea, and the EU was performed and a plan for the construction of a Chinese database was proposed.The following conclusions can be drawn.
Based on the literature review, ten building materials (concrete, rebar, cement, aggregate, brick, stone, steel frame, glass, insulation, gypsum board) were selected as the major building materials and the scope of the analysis included three major environmental impact categories (global warming, acidification, and eutrophication).
Based on the comparative analysis of the environmental impact factor databases of each country, similarities and differences were derived.The environmental impact of the GWP on concrete, cement, glass, and sand and the environmental impact of the AP on concrete, cement, and gypsum board were determined to be similar.Furthermore, the EP environmental impact values of China and the Republic of Korea were similar, with the exception of glass.These results suggest that, when a building material database is insufficient or unavailable for a building LCA, a similar database on another country can be applied.
Utilizing the outcomes of the comparative analysis of environmental impact factor databases from various countries, a database specifically tailored for building materials in China was established.Preference was given to databases featuring environmental impact factors closely resembling those of China during the construction process.In instances where significant variations in environmental impact factors existed, the South Korean database, characterized by smaller regional differences compared to China, was employed.
The case study results revealed an 11% deviation between the environmental impact assessment results derived from the new database and those relying on the CLCD.Despite yielding lower assessment outcomes compared to the Chinese database, the enhanced accuracy in environmental impact assessment for building materials was evident due to the new database's inclusion of more detailed specifications for each building material as opposed to the CLCD.The suitability of the new database for application in China was affirmed.
In this study, the similarities and differences between the environmental impact factors for building materials of each country were analyzed and evidence was provided that an overseas database can be used if the Chinese database is insufficient.It is expected that the accuracy of the LCA for buildings in China can be further improved by supplementing China's environmental impact factor database for building materials.However, because the differences between the building material environmental impact factors of some countries were relatively large, it is necessary to create a list of impact materials by country and environmental impact category in the future and conduct an additional comparative analysis of the basic materials and energy consumed in the production process of the material.

Figure 2 .
Figure 2. Global warming potentials of Korea and the EU in comparison with that of China.

Figure 3 .
Figure 3. Acidification potential of Korea and the EU in comparison with that of China.

Figure 2 .
Figure 2. Global warming potentials of Korea and the EU in comparison with that of China.

Figure 2 .
Figure 2. Global warming potentials of Korea and the EU in comparison with that of China.

Figure 3 .
Figure 3. Acidification potential of Korea and the EU in comparison with that of China.Figure 3. Acidification potential of Korea and the EU in comparison with that of China.

Figure 3 .
Figure 3. Acidification potential of Korea and the EU in comparison with that of China.Figure 3. Acidification potential of Korea and the EU in comparison with that of China.

Figure 4 .
Figure 4. Eutrophication potential of Korea and the EU in comparison with that of China.

Figure 4 .
Figure 4. Eutrophication potential of Korea and the EU in comparison with that of China.

Figure 5 .
Figure 5. LCIA results for the case study building (by database).

Figure 5 .
Figure 5. LCIA results for the case study building (by database).

Table 1 .
Policies relevant for a building life cycle assessment.
Table 3 is a literature review table summarizing the existing studies discussed above.

Table 2 .
Life cycle assessment database.

Table 3 .
Review of the existing literature.

Table 4 .
Previous research results on major building materials.

Table 5 .
Life cycle inventory database of major building materials.
Note: a: National LCI Database, b: National Environmental Information Database, c: National LCI Database for Construction Materials.

Table 6 .
Equivalents by environmental impact category.

Table 6 .
Equivalents by environmental impact category.

Table 7 .
Environmental impact factor database proposed for Chinese construction materials.
○: Proposed databases for each building material.

Table 8 .
LCI database connection based on the cumulative weight contributions of major building materials.

Table 9 .
Results of the evaluation of the environmental impact by building material (by database).