I hope that this question qualifies for worldbuilding. Take my apologies if it's too specific / not specific enough.
In a post-apocalyptic desert-like environment with only a few million people left worldwide, for hundreds of miles, one warlord has a monopoly of growing food. Water is rare yet available, but plants are not.
Our warlord wants to trade food (i.e. nutrition) for gasoline, but paranoidly wants to ensure that not even a single live grain/seedling/egg/whatever will ever leave his farms and jeopardize his monopoly. Nothing that he sells may be able to reproduce/grow.
Hence he withdraws blood from his underlings, and literally trades blood for oil.
- What single source of food is hardest to keep from reproduction while still being nutritious? (I need something resilient to point at and say "hey, since that´s all they have left, it absolutely makes sense to save my blood-for-oil-joke")
- Is there a reason while human blood (700kcal/liter) would be unsuited as nutrition in a life-or-death situation?