## 3 Literature Review  
### Environmental Labeling (International Organization of Standardization (ISO) 14020s)  
Eco-friendly product certification is a key method for ensuring superior environmental performance compared to other products in the market [20]. Environmental labeling provides information that helps consumers recognize and choose products with superior environmental performance, encouraging the purchase of eco-friendly alternatives while motivating companies to develop environmentally friendly products [21]. Since 1993, the ISO has developed the ISO 14020 series as an international standard for the environmental management of products. The ISO standard for environmental labeling is presented in Table 1 [22].  
Type I environmental labeling is granted to products whose environmental impact has been evaluated across various life cycle stages--production, distribution, consumption, and disposal--by an independent third-party certification agency [27]. This concept was first introduced in 1979 by Germany's Blue Angel environmental label and later adopted by Japan, the United States, and the European Union [28]. As of 2015, this labeling is used in 47 countries worldwide and is known as EPD products in Korea, managed by the Korea Environmental Industry & Technology Institute (KEITI). The EPD applies to products for which the environmental impact is quantitatively assessed across seven major environmental categories, covering all stages from raw material collection to production, distribution, use, and disposal [25].  
Type II labeling is defined in ISO 14021 as a type of labeling applicable to products that can be labeled without independent third-party certification if the company demonstrates secured environmental performance [22]. Many companies display symbols or phrases indicating their product's eco-friendliness on packaging and engage in green marketing [29]. Several countries, including the United States, Canada, Japan, and those in Europe, have adopted ISO 14021 to enforce regulatory standards aimed at preventing false or exaggerated advertising by companies [22]. In Korea, this labeling is applied by KEITI to low-carbon products that have undergone additional CE reductions [17]. Low-carbon certification is granted to products with a carbon footprint below the maximum allowable CE or exceeding the minimum required CR rate. The maximum allowable CE refer to cases below the average CE for the product group, whereas the minimum reduction rate refers to a reduction of 3.3% or more in CE compared with similar products. KEITI comprehensively manages both Type I and Type II EPD-certified products, as well as low-carbon EPD-certified products [30].  
Recently, the social recognition and importance of carbon neutrality have grown, increasing demand for reducing embodied carbon in the production stage of materials. Consequently, the number of EPD-certified products, for which environmental impact is evaluated across all stages and CE are further reduced, continues to increase. Figure 2 illustrates the status of EPD-certified products in Korea [17].  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Standard** & **Year (yyyy:mm)** & **Environmental Labeling** \\ \hline ISO 14020 [23] & 2000.09 &
\begin{tabular}{c} Environmental Labels and Declarations \\ (general principle) \\ \end{tabular} \\ \hline ISO 14021 [24] & 1999.09 & Type II (self-environmental claim) \\ \hline ISO 14024 [25] & 1999.04 & Type I \\ \hline ISO 14025 [26] & 2006.07 & Type III \\ \hline \hline \end{tabular}
\end{table}
Table 1: International standard for environmental labeling (International Organization of Standardization (ISO) 14020s).