Our waterways are becoming more and more polluted due to PFAS, plastics, medicines, drugs, and new chemicals made by companies that just hand over the responsibility of cleaning to plants paid for by public moneys. Detecting the different chemicals and filtering them out if getting harder and harder. Could the simple solution of heating up past a point where even PFAS/forever chemicals decomposes (400C for PFAS, 500C to be more sure about other stuff) be alright?
Grain lasts years. Starchy tubers (which we are uniquely evolved to consume and what was actually what supported the energy requirements of our large brain in pre-technological times) last all winter, or longer if you don’t dig them up. Salt preserves for years. So does pickling. Hell, even dogs are smart enough to preserve food by burying it in an anaerobic environment. A whole lot has to go wrong for the milk from an animal to be the margin by which a person survives, and by that point the animal has probably already been slaughtered. Exceptions like African bushmen who consume blood as a primary staple are quite rare.