Trends in scientific literature on energy return ratio of renewable energy sources for supporting policymakers

The scarcity of fossil fuels and their environmental impact as greenhouse gas (GHG) emissions, have prompted governments around the world to both develop research and foster the use of renewable energy sources (RES), such as biomass, wind, and solar. Therefore, although these efforts represent potential solutions for fossil fuel shortages and GHG emission reduction, some doubts have emerged recently regarding their energy efficiency. Indeed, it is very useful to assess their energy gain, which means quantifying and comparing the amount of energy consumed to produce alternative fuels. In this context, the aim of this paper is to analyze the trend of the academic literature of studies concerning the indices of the energy return ratio (ERR), such as energy return on energy invested (EROEI), considering biomass, wind and solar energy. This could be useful for institutions and to public organizations in order to redefine their political vision for realizing sustainable socio-economic systems in line with the transition from fossil fuels to renewable energies. Results showed that biomass seems to be more expensive and less efficient than the equivalent fossil-based energy, whereas solar photovoltaic (PV) and wind energy have reached mature and advanced levels of technology.