Apologies if I'm being an imbecile, but I'm missing something (or possibly the Black Crusade rules are missing something).
Given the presence of the Nutrient Recycling option for legion armour, and the Warp Eater trait, it sort of begs the question of what happens if you don't have either - i.e. what, assuming survival skill checks are failed, are the rules for starvation?
The player in question is a chaos marine on a wilderness planet, who (for various reasons) isn't in a position to actively go hunting.