That, and most of the other nutrients which was needed to grow the vegies ( like phosphates and potassium) are flushed into the toilet. There will be no long term permaculture without cycling those back at some point. Otherwise, organic or not, this will remains an wasteful open loop.
It seems if we would only put brains on the matter, there is no physical laws to be broken to fix this issue.
A great example is the Shift Project think tank in France putting together a systemic plan [1] that:
1) brings an entire country to actually respect its carbon budget (relative to its population) necessary to stay within 2C of global warning
2) do this while keeping a job for everybody, in a systemic way (consistent across all industries)
3) does not assume any new miracle technology
4) does not assume to go the autocratic way
5) and more importantly, assumes all of this must be possible under economic contraction, because energy/economy decoupling is for the foreseeable future, a chimera [2]
