## 3 WEEE and ELV Management and Circular Economy  
A multi-way approach to mitigate the effects of F-gases on the climate must include: (i) the phase-down of high GWP compounds and seeking new alternatives; (ii) the improvement of equipment to prevent leaks and the promotion of good handling and operation practices to prevent emissions; and (iii) the efficient management of the produced F-gases, of those recovered from EoL equipment, and of those recovered when retrofitting existing installations. According to the EU F-Gas Regulation, the release of refrigerants into the atmosphere is explicitly prohibited and subjected to penalties. Therefore, refrigerants must be recovered for reuse or destruction [23].  
However, much improvement still needs to be achieved globally in the recovery and management of F-gases and other refrigerants. There are two major sources of F-gas residues, WEEE and ELVs, which require different management approaches. Despite having legislation that regulates these procedures and having economic capacity to implement efficient (and sometimes expensive) technologies, developed countries still face challenges to efficiently manage refrigerants. In Portugal, data from 2017 revealed that only 8.7% of the refrigerants were recovered from equipment and systems and further treated, most probably due to incorrect management by non-certified operators [35]. In developing countries and emerging economies, refrigerant management is even more challenging, mostly due to the lack of efficient legislation, difficulties in implementing technologies, and to the dismantling of equipment to recover metals and other material with no concerns for the potential refrigerant release.  
The emission of refrigerants from air conditioning systems in vehicles is challenging due to the high leakage rates in the systems, to the unintentional release of refrigerants due to car accidents, and to the improper recovery and management during the dismantling process. In the EU, the directive 2000/53/EC requires Member States to ensure that EOL vehicles are dismantled and hazardous materials, including HFC refrigerants, are removed [36]. According to Directive 2006/40/EC, from 2017 onward the air conditioningsystems of all new vehicles cannot contain F-gases with a GWP higher than 150 (e.g., R-134a) [37]. Despite the legislation that determines the switch to lower GWP alternatives in vehicles, the mechanisms to manage the F-gases from EoL equipment present flaws. To reduce the release of F-gases into the atmosphere, they must be recovered from EoL equipment for further destruction or reuse. However, since most workers are not well trained, few incentives are given to the recovery and disposal processes, and to the obligation to pay the costs of disposing, most operators responsible for recovering the refrigerants end up releasing them into the atmosphere. Moreover, a great amount of refrigerant is lost during the system's lifetime. Upon recovery, F-gases can be managed in two main ways. They can be destroyed or they can be reprocessed for further reuse (Figure 2) [38]. The first approach follows a linear economy concept and has the advantage of using already implemented technologies and facilities to achieve an almost complete elimination of the F-gases [38,39]. However, emissions of GHGs occur during the transport of the F-gases from the site where they were recovered to the incineration facility and during the incineration process. The second approach follows a circular economy concept and has the advantage of allowing the reuse of value-added refrigerants to reduce the pressure on the supply chain of these compounds, reducing the release of GHGs during the production of new compounds and during their destruction [38]. Moreover, if the reprocessing of the F-gases occurs in the same place where they were recovered, additional benefits in terms of costs and GHG emissions are obtained since the transport (sometimes over long distances) is avoided.