## 2 Background
### Power-to-Gas Deployment in a Circular Scenario  
Different scenarios for PtG deployment have been estimated based on the assumption that the electrolysis capacity demand varies depending on the energy market scenarios, the expected environmental targets, and the energy transition pathways [19]. [PERSON] et al. (2014) determine the optimum PtG capacity from an economic perspective using flexibility options of hydrogen production for short-term storage systems, and increasing PtG capacity in interaction with the most relevant competitive option [10]. Furthermore, [PERSON] et al. (2015) define a 2030 scenario for different parameters, efficiencies, and costs of technologies, demonstrating the expected high impact of PtG for future energy systems [20].  
[PERSON] et al. (2016) simulates two scenarios of potential PtG capacity until 2050 in which the German power sector achieves 100% of its electricity generation from RES [13]. The results show substantial cost reductions and price declines for methanation and electrolysis [12]. [PERSON] and [PERSON] (2017) explore the application of PtG to the storage of excess renewable electricity to meet heating demand, when the RES share is assumed to increase to up to 50% in different scenarios [67].  
[PERSON] et al. (2017) consider that PtG is integrated into the electricity market in Switzerland and include other services related to the generation of low fossil-carbon gas [57]. [PERSON] et al. (2014) propose three scenarios for hydrogen production based on the capacity of the distribution network, the RES generation plant, and the size of the electrolyzer [56]. [PERSON] et al. (2020) develop six scenarios under certain policy constraints, such as cross-border electricity trade and greenhouse gas emission costs, within the time horizon of 2015-2050 in 5-year intervals [65]. Finally, [PERSON] et al. (2018) define three possible scenarios to quantify the growth of wind and PV generation and the PtG capacity that would be installed in Spain [14].  
The PtG scenarios developed by the previous studies often consider an electricity surplus of RES installed capacity [14; 31; 68]. However, these scenarios are often subject to uncertainty because of sectoral regulation, economics issues, and markets, in addition to the technology evolution of these systems [14]. Thus, our attempt to define the future socio-economic impacts of PtG deployment is pioneering research in the actual phase of the development of this technology.  
Among the studies that are similar to our object of analysis, we highlight the research carried out by [PERSON] et al. (2016), which focused on carbon capture and storage (CCS) using several socio-economic indicators [69]. These authors calculate the incremental impacts linked to employment, gross value added, and import dependency by integrating techno-economic bottom-up data with a macro-economic multi-regional input-output model. Although these indicators are of interest and can be implemented for PtG, it is necessary to expand the specific analysis about the impacts of these technologies given their future expansion.  
In summary, the economic and environmental impacts linked to the evolution of PtG in the coming decades have been analyzed in previous studies. However, social impacts of PtG technology have not been addressed in depth in the long term. Nor have these studies addressed the issue of PtG from the perspective of a CE. For this reason, in this paper we estimate the socio-economic impacts of this technology in different temporal spaces, taking into account the CE principles promoted by institutions and governments, and the institutional pressures on climate change [70].  
Based on the previous considerations, the following research question is raised:  
**RQ 3:**: _What are the most widespread PtG-related determinants factors in a CE scenario?_  
These research questions are answered by analyzing a case study at the territorial level from a CE perspective. The main results are summarized in the following sections.