## 1 Introduction
Despite the current barriers of PtG, which relate mainly to its high costs and efficiency rates obtained at the development stage, it has been identified as a cost-efficient option for renewable gas and a long-term storage solution. PtG contributes to the decarbonization of different sectors and allows the substitution of European energy carriers based on fossil fuels [13]. However, at present, these technologies face numerous barriers to their deployment in the European Union, and, in particular, in Southern Europe. The academic literature has analyzed the impact of PtG on future energy systems in European [10; 12; 14; 17] and non-European [18] countries. In particular, the impact of these technologies in the German energy transition scheme has been examined extensively by different authors [11; 13; 19]. Technical parameters and technology costs have been analyzed, and a consensus reached that PtG is a sustainable solution for decarbonization. These systems are close to being exploited at a larger scale, depending on the technological development of RES [10; 20]. Nevertheless, the socio-economic impacts of the deployment of PtG is an underexplored line of inquiry. Currently, two main gaps exist in the literature. Previous studies explored technical and economic impacts of PtG, but have not analyzed how socio-economic impacts related to these technologies can be measured. Second, most studies that looked at the incentives and barriers to PtG have not delved into other non-technical barriers that affect these investments in a circular model [21]. Thus, we address these two gaps from a circular perspective. Based on this overview, the aim of this paper is to explore the determinants and barriers for PtG technologies to enhance the understanding of investment in innovative energy technologies and to estimate the socio-economic impacts related to the use of these systems in different scenarios. Thus, we analyze future scenarios and investment in PtG technologies (in particular, power-to-methane) using data obtained from 15 semi-structural interviews of the Spanish representatives of the main groups of stakeholders: private companies that operate in the energy sector, research and development (R&D) institutes, public administration, and other organizations involved in the energy transition in the area. A heuristic approach to the socio-economic impacts of future transactions related to PtG facilities is also offered using the main categories of economic and social impacts that are estimated from a circular perspective. In summary, a contribution of this study is the measurement of the impacts of the use of PtG technologies in future sustainable energy markets for the exploitation of renewables in a zero-emission scenario based on the foundations of the CE. We also contribute to the definition and analysis of the determinants and barriers for the use of PtG technologies. In particular, a case study is analyzed to determine which incentives are more effective in mobilizing investments in the area. The remainder of this article is structured as follows: Following the introduction, we explore the background of this research. In Section 3, a methodology for evaluating the determinants and estimating the socio-economic impacts of PtG deployment in a territory is proposed and applied to a case study. Results are subsequently analyzed. After a discussion about the determinants and incentives to these technologies in Southern Europe, we conclude by summarizing out recommendations for policymakers, academics, and practitioners in Section 4.