## 3 Methods
### Digital Technologies Enabling the ReSOLVE Framework
#### 5.1.4 DTs Enabling the Loop Area  
The Loop area can benefit from the adoption of different DTs (Figure 10). Particularly, a good variety of DTs proves to foster actions related to the disassembly of products. An interesting role is played by AR, which could be useful in planning the disassembly sequence, as it would allow the visualization of all the information and equipment needed in the process, besides helping in training operators [96]. ROBs also have an interesting role in the disassembly process [85], although issues in terms of economic feasibility may pose limitations [83]. As for the determining and optimizing of the disassembly process, both SIM [85; 91] and BDA for mining a repository of disassembly processes [70] are considered as possible options.  
The remanufacturing process requires different data related to the product, i.e., its status, maintenance history, disassembly and reassembly [117]. From this perspective, the use of IoT via sensors would be helpful to track the product history, through real-time monitoring that could bring positive effects in different processes [89; 118]. However, although few cases can be spotted where IoT is relevant for looping strategies, empirical studies show that IoT is not largely used for product remanufacturing [95]. Additional opportunities have been conceptualized from the integrated use of IoT and AM, but the realization has not been demonstrated [68]. AM nonetheless can contribute to sustainability, presenting lower cost related for example to set-up, and can play an important role in the loop area when the workload is distributed along the different tiers of the supply chain [68; 119]. For the latter point, the use of an HVSYS would allow real-time data management throughout the entire chain, thus facilitating the loop strategies [68]. Lastly, SIM can assist remanufacturing processes, as discrete event simulation models are essential to determine the quality of a product [91].  
As for the recycling process, IoT would provide benefits in terms of monitoring and tracking [103], enabling looping [71; 95]. Two relevant aspects emerged as connected to the adoption of IoT: first, to make proper decisions, data should be collected with an HVSYS perspective [74]; second, as many data would be collected, BDA becomes fundamental to manage the complexity [102]. Lastly, the use of ROB would facilitate the recycling process, while also bringing benefits from a social sustainability perspective [103]. Additional insights are provided highlighting a strong correlation between the adoption of recycling practices and the adoption of BDA, ROB and AM, suggesting also that I4.0 might allow greater integration among the partners of the value chain [66]. Nonetheless, several issues emerge trying to link the concept of CE with the one related to industrial systems; incorporating CE into industrial networks requires a change in the economic paradigm [120] that would be allowed only by a strong willingness of all the involved partners to embark in this transition [121]. The main obstacle and critical resource for the transition is the trust among the partners [122], which becomes even more pivotal if the transition is enabled by DTs [123]. Additionally, moving from a single firm to the value chain and then the industrial system would require the identification of the best set of DTs to use [124].