Building on the work of the previous work packages (especially work package 4), work package 5, led by DBFZ, will identify promising concepts for biomethane (both from anaerobic digestion and gasification) and power-to-methane synergies, as well as potential hotspots for physical links between both technologies. Furthermore, open questions and potential barriers for the sustainability assessment and certification of Power-to-Methane concepts will be analysed and appropriate solutions will be developed.