I had a thread a couple of weeks ago about smoking half a cigarette after 9 years as a non-smoker. The craving was obsessive and consistent. I haven't had another and bought a nicotine free vape (which is rubbish and has done nothing to diminish the craving).
Anyhow the cigarette craving has now developed into a craving for licking and eating cigarette ash! Gross! So definitely pica.
The last time i was PG it was shoe polish and I would sit watching tv with a tub of shoe polish which I would occasionally sniff. I was very close to eating it too but refrained 
So now I'm craving fag ash...anyone know an alternative?! I think about it all say long and want to smoke just so I can get to eat the ash at the end.
WTF??!