If modern society collapses, starting back over with the same approach isn't the best plan. Cheap hydrocarbons are sort of like VC funding. They have allowed society to advance extremely rapidly, in a totally unsustainable way. We have yet to find out if we can stick the landing on transitioning to a sustainable lifestyle. It's possible that humans just aren't wired in a way to responsibly manage the risks introduced by sufficiently advanced technology, at least not at the current rate of change.
In a post-apocalyptic world, survivors should really be rethinking the approach that brought that about. Avoiding the cheap hydrocarbon consumption phase might result in a much longer lasting civilazation next time around.
In addition to coal that I mentioned above, it should be possible to have industrial society with renewables. It wouldn’t be as high energy as ours or as industrialized. But if they knew the science and some technology they could skip the big iron phase.
Early power could come from burning wood and windmills. That doesn’t have enough power for smelting iron, but there is more than lots of iron, Electricity could come from concentrated solar, wind, hydro, or geothermal. Nuclear would be the big jump.
In a post-apocalyptic world, survivors should really be rethinking the approach that brought that about. Avoiding the cheap hydrocarbon consumption phase might result in a much longer lasting civilazation next time around.