”nitrogen-rich fossil fuels that feed our culture“ wow this article is really badly researched. the problem is of course real and has been described very well by William Crookes in 1898. The answer back then was the development of the Haber-Bosch process.
The input was originally hydrogen from coal not natural gas which shows that the process is a bit more adaptable than this article makes us believe.
hydrogen can be obtained from many sources (including as a pure substance from wells as white hydrogen) and the reason why we use natural gas today is because it is much cheaper than the alternatives, not because other source materials would not scale as well.
how we will be creating inorganic nitrogen fertilizer in the future is a question to be solved but it is not an insurmountable problem – more like an upcoming shift in our economic practice because we will have to switch to more expensive sources.