There is no way of measuring this, as far as I can tell, as a long seasoned measurer of things, would be interesting to see details of how it might have been tested.
How did they deduce how much is energy it took to construct the plant itself, for example? This has to comprise both metabolistic / chemical energy correlating with the energy of the information of the plant, that can be expressed digitally, describing the complex structure of the plant. Even if that was established, how then did they measure the energy that further went from sun into earth as nutrients?
Conventional science has never even signed energy in and out of the system of Earth from the sun, so it really has no chance as stands, of seeing any evidence showing solar is perfectly fine, and will support thousands of times the current population on Earth, after we move from destroying it, to creation which is added to it rather than removed.
Hey-ho, if you say you won't live to see real change, then I guess you might be right there, again more self fulfilled prophecy, imho :)