i saw a programme where they said it had vinyl, engine oil, manure etc anything to bulk it out. alot of come from places like morocco where the workers will add almost anything to it to bulk it out and make it heavier so they can be paid more. Can't really blame them, i think its the fault of the fools who would choose to smoke that mish mashed rubbish over a natural herb!
jut about anything and everything and everything which they can get in there, i have actually had "solid" with a piece of tescos bag in it, never again lol, like jacobsmummy says smoke the natural stuff if your wanna get high
Also just another thing if you get weed that feels kinda sandy dont smoke it, its industrial etchant thats sprayed on after the thc has been shaken off apparently the etchant isnt too good for your throat and lungs.