The poop fertilized plants, the plants were harvested, some of them were turned into bread, others fed a pig, and that's what you're eating. Some of the poop decayed and was released as gases into the air, which were then recaptured by the plants, by bacteria in the roots of soybeans, and by Haber-Bosch factories (confusingly also called plants) which made synthetic fertilizer to fertilize the plants further.
You are recycling your sandwich, made from poop, into more poop.
This is the reflection on the disgusting nature of food and its link to the interdependent arising of all things. Your existence is inextricably linked to the existence of the pig and the poop. They are not separate processes; they are different focuses in the same process.