It's a great question. However, that's just a portion of specifically stalks from corn, wheat and grain. That's one of about ten biofuels pathways with waste biomass.

The larger point is that we have so much waste biomass sitting around generating methane that converting it to biofuels is a strong solution for the climate problem it already creates, and for the need for high energy liquid fuels for actually hard to abate transportation sectors.

Balancing comparative needs so that crop nutrients are provided effectively and efficiently is just market forces moving forward, not a negative concern on biofuels, in my opinion.