## 4 Discussion
### Challenges and Limitations  
The implementation of RFID technology in the EU fresh milk supply chain faces several challenges and limitations that need to be addressed for its widespread adoption. One of the significant technical challenges is the reliability of RFID systems in real-world retail and supply chain settings [28]. Ultra-high frequency (UHF) RFID tags, which are commonly used in the supply chain, struggle with readability issues near liquids and metals, as liquids tend to absorb RFID signals while metals reflect them ([PERSON] et al. 2009 [29]). This issue is particularly pronounced when tags are applied to products with high water content, such as milk. Additionally, the limited read ranges--typically 1 m for low-frequency RFID systems and up to 3-4 m for UHF systems--require more reliable and extended-range readers to ensure effective data collection across various settings. Ensuring accurate and consistent readings is also complex as improper tag orientation can lead to missed readings, undermining traceability efforts. Another important limitation is the exclusion of refrigerated storage at distribution centers, which was not modeled due to lack of detailed operational data. However, we recognize that this stage can represent a significant share of energy use in the cold chain. In particular, one of RFID's key logistical benefits is its ability to reduce storage duration through improved inventory turnover. By omitting energy use in refrigeration, we likely underestimate the full extent of environmental savings associated with RFID deployment. Furthermore, while our 2035 scenario offers valuable insights into the potential long-term environmental benefits of RFID adoption in the milk supply chain, it is based on static assumptions and linear extrapolations. It does not consider evolving factors, such as decarbonization of the EU electricity mix, advances in RFID materials, or innovations in digital logistics. These dynamics could significantly influence both the absolute and relative outcomes. Future research should incorporate dynamic modeling frameworks to more accurately capture such complex interactions. Cost remains another critical barrier. Despite technological advancements and reduced manufacturing costs, RFID tags are still considerably more expensive than traditional barcodes, especially when considering large-scale deployment across the entire dairy supply chain. Passive tags, used for general retail, cost between 5 to 10 cents each, which may still be prohibitive for products with slim profit margins. Active tags, which cost up to $100 per tag, are impractical for widespread use on lower-value products. The high implementation and maintenance costs have discouraged major retailers and stakeholders in the dairy industry from fully embracing RFID technology, particularly in the face of confidentiality concerns and the challenge of maintaining profitability in a competitive market [27]. Another challenge is recycling. RFID tags consist of multiple components--adhesives, computer chips, antenna metals, and conductive inks--that can interfere with conventional recycling processes [18; 19]. For example, copper antennas can compromise the quality of recycled steel, while adhesives and chips can complicate plastic recycling, especially for PET and HDPE materials. These recycling challenges present a conflict between enhancing traceability through RFID and achieving environmental sustainability. Addressing this conflict will require the development of recyclable or biodegradable RFID tags that can seamlessly integrate with recycling streams without causing contamination. Standardization issues further complicate RFID deployment across the EU. Frequencies allocated for RFID usage vary across countries, resulting in discrepancies that limit cross-border compatibility. For instance, the EU and the U.S. use different UHF frequencies--868 MHz and 915 MHz, respectively. As a result, tags that operate efficiently in one region may face compatibility issues in another.