## 4 Conclusions  
In this study, we analyze the determinants and barriers for PtG systems to enhance the understanding of the investment in innovative energy technologies and to support effective policymaking in an energy transition scenario. These results fill two gaps in the literature by providing an extensive analysis of determinants and barriers for PtG technologies, and an innovative methodology for estimating, from a circular perspective, socio-economic impacts of these technologies in different scenarios. The results show the most relevant barriers for PtG are linked to economic aspects such as the payback period, the high volume of the initial investment, and the price of equipment or the difficulties related to financing it. Another set of barriers is related to legislation issues and/or subsidies to promote \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multicolumn{1}{c}{\multirow{2}{*}{**Factors of Analysis-PtG Deployment**}} & \multicolumn{2}{c}{**Pessimistic (with Barriers)**} & \multicolumn{2}{c}{**Pessimistic (with Usual (Energy & \
\begin{tabular}{c} **Business as** \\ **Usual (Energy** \\ **Incentives)** \\ \end{tabular} &
\begin{tabular}{c} **Optimistic (with** \\ **CE Incentives)** \\ \end{tabular} \\ \hline Barrier & (a) High price of electrolyzer & \(-0.1\) & \(0\) & \(0\) & \(0\) \\ Barrier & (b) Payback period & \(-0.1\) & \(0\) & \(0\) & \(0\) \\ Incentive & (c) Feed-in-tariff & \(0\) & \(0\) & \(0.3\) & \(0.3\) \\ Incentive & (d) Regulation & \(0\) & \(0\) & \(0.3\) & \(0.3\) \\ CE Incentive & (e) Incentives to CE (RES) & \(0\) & \(0\) & \(0\) & \(0.2\) \\ CE Incentive & (f) Limits to CO\({}_{2}\) emissions (CE) & \(0\) & \(0\) & \(0\) & \(0.2\) \\ \hline \hline \multicolumn{1}{c}{\(\lambda_{2025}\)} & \(-0.2\) & \(0\) & \(0.6\) & \(1\) \\ \multicolumn{1}{c}{\(\lambda_{2030}\)} & \(-0.3\) & \(0\) & \(0.65\) & \(1.1\) \\ \multicolumn{1}{c}{\(\lambda_{2050}\)} & \(-0.4\) & \(0\) & \(0.7\) & \(1.2\) \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Matrix of factors for the PtG scenario analysis. the technology. Both aspects were highlighted by most of the interviewed experts as incentives to PtG deployment. It is foreseen that decisions to investment in these technologies produce incremental effects in the long term. Not investing in the 2025 scenario generates cumulative socio-economic impacts that imply a posteriori benefits in employment and the capture of CO\({}_{2}\) emissions. However, not making these investments, or making lesser investments, could harm future PtG deployment in terms of installed capacity and related impacts. At present, overcoming the barriers that hamper investment in PtG systems partially depends on public stimuli. To overcome these challenges and help firms in their transition toward circular economic models, favorable conditions are needed. Policymakers must play a relevant role as a driver for the adoption of the CE to foster the adoption of innovative energy technologies that improve the closing of material loops. Exploring barriers and incentives is a contribution to the academic literature that can be applied by practitioners to the decision-making process of investment in energy technologies. These results offer information for effective policymaking. In addition, the developed methodology for the estimation of socio-economic impacts can be extrapolated to other countries where the CE will be promoted. Policy and industry stakeholders aiming at promoting innovative and sustainable energy systems can use these findings. Practitioners of the energy sector can calculate the socio-economic impacts of their investments to disclose them in terms of sustainability in non-financial reporting. The main findings of this study concern the methodology used to define and measure the main socio-economic impacts of future investments in innovative energy technologies such as PtG.