As an even simpler example, hydrocarbons can be burned to water and C2O. You can feed those to plants just like anything else.
(But going that route would waste a lot of energy.)
(But going that route would waste a lot of energy.)
I didn't say that's what you should do or that it makes sense.
Merely as an illustration that you can start with some toxic substances and feed them to plants, and be very happy eating those plants.
Of course, that doesn't apply to everything. Heavy metals stay bad for you.