The human digestive system is not 100% efficient. No system is. I have had a method of filtering and re-prepping my stools for consumption. I estimate that I can survive, meal wise, off USD$0.75 per day purely by sifting, straining, rinsing, and dry baking the contents of each and every stool, then mixing with filler material such as seasoned corn meal.
Pic is my entire stool, combined with an extraction tincture, prior to first mesh pass. You will want to keep a low fat diet, as fatty stool is impossible to clean, fat becomes rancid, and your first meal of dry roasted fatty stool will probably make you want to kill yourself. I have been immunised against all types of hepatitis so I do not advise you to try this until I provide more information.