It wouldn’t be so bad if they wouldn’t keep emphasizing urine as an example.

Food scientists working for the US military have developed a dried food ration that troops can hydrate by adding the filthiest of muddy swamp water or even peeing on it.
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The water seeps through the membrane into the dehydrated food on the other side. As it dissolves large molecules in the food, it creates a very high concentration solution. The osmotic pressure created then draws more water through the membrane.