There are many power-to-x chemistries that I think are much easier than methane once you grow out of easily available concentrated CO2. They don't quite reach t

There are many power-to-x chemistries that I think are much easier than methane once you grow out of easily available concentrated CO2. They don't quite reach the energy density of hydrocarbons, but that's not much of an issue for stationary storage in the "seasonal scale battery" use case. Almost everything can serve as an "oxidizable" in reduced form, and if the resulting oxide isn't gaseous you lose the "tank gets lighter" effect that is only really important for aircraft but win a solution to the capture problem for completing the cycle. Iron for example is said to get an energy density roughly comparable with coal. Another x in power-to-x is ammonia, which could be used in an open cycle scenario where DAC would be trivial because so much of our air is nitrogen.