It's using 'current carbon' which is basically the same thing. Plants grow using CO2 in the air, we burn the plants and that CO2 is released again. If we just left the biomass to rot on the ground it'd produce CO2 and / or Methane depending on the type of decomposition it underwent.
Verses plants and animals lived millennia ago, died, got compressed by huge geological forces and finally we come along and extract it and burn it.
Need to is a bit of a stretch. Manure, urine, nitrogen fixing legumes are all potential fertiliser.
In addition growing deciduous crops rather than annuals and good soil management practices and can help reduce or eliminate additional fertiliser requirement.
Verses plants and animals lived millennia ago, died, got compressed by huge geological forces and finally we come along and extract it and burn it.