I think the point is explained further below - the author is making a reference to the amount of energy required if the world had a developed standard of living

I think the point is explained further below - the author is making a reference to the amount of energy required if the world had a developed standard of living, not saying that we would ever use natural gas down there. > It can be done. In the near term, it is conceivable that already-common sources of renewable energy like wind and solar power can meet most of the need. Things would be easier if existing nuclear power technologies were expanded, or at least if we avoided shutting such plants down prematurely. > But the more fanciful world described above—the one in which, thanks to plentiful energy, the world has eliminated want—is possible only with continued innovation. In the long term, the renewables we currently have will hit a ceiling.