I think it could be related to an
eating disorder called
pica, which is a compulsion to eat non-food items, such as dirt, chalk, paint chips, etc. The disorder is generally associated with a nutrient deficiency, which results in cravings for non-food items. I haven't heard too much about people's struggles with this particular eating disorders, so I am not sure how long it typically lasts, or exactly how it is treated. Sorry, I know that isn't much help.