That would never make sense to do. The atmosphere is heavily enriched with CO2 already, so plants don't need help obtaining it. If you want to grow plants in an area where water is so scarce you have to import it, but you have oil, don't burn your money: sell the oil and buy water.

Uh, yes? You'd be a fool to burn oil just as a source as CO2 and water.

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.