After seeing posts about the South Park episode it got me wondering about this theory. I searched relevant terms on qanon.pub but couldn't find anything related this this theory. He doesn't seem to have ever once said 'adrenochrome' and 'sacrifice' returns 20 hits but they are all out of this context. Searching and reading up on child/children/kids also gives me no useful intel as to this theory.
What is the origin? From what I can tell, it did not come from Q.
Q said to check out Evergreen, Hillary’s secret service name. That led to researchers finding an Evergreen shipping company. I believe that connects to child trafficking.