Conservation of mass?
Do they understand that producing energy and fertilizer using the bodies of animals is less efficient than producing the same number of calories or mass of nitrates from plants+less-energy-than-is-required-to-raise-the-animal-in-question?
Using animals as fertilizer is a nessessity brought about by phasing out crop rotations. If we just rotated our fucking crops that would naturally replenish the soil. Instead we have endless fields of corn year after year