Just wondering if anyone has tried using burnt dead or discarded plants as fertilizer for new plants, and how much of the nutrients you can recycle if you reuse the waste from the previous harvest. My idea was simply to burn the plant matter, possibly in an oxygen rich environment, to be left with only ashes, and then either do some more chemical separation or just use the ash as it was. From my limited understanding all the Carbon and Hydrogen should just be turned into CO2 and H2O and I should be left with the nutrients (ideally I would conserve the CO2 so I can have a CO2 rich environment to speed up the growth).
Has anyone here done something similar?
EDIT: I was rather tired when I asked the question it seems :/ I meant to ask specifically about burning the plants, not composting (I want to extract energy while burning them)