It’s a very unique and distinctive smell. Almost smoky is the best way I can describe it. Other plastic bags don’t smell that way, so what is it in black bin liners that gives them that particular aroma?
My bet is that there is some degradation of the polyethlene producing some volatile organic compounds that produce that smokey smell. When Sainsburys switched to their first generation recycled plastic bags they had the same smell too.
This paper suggests some compounds that might be likely causes, but the research wasn’t done on bin bags.
Any dopers got access to a gas chromatograph and be willing to run a sample?
It is because black bin bags are made from the lowest grade polyethlene. They contain all the dregs and and manufacturing impurities from making higher grade polythene. This is why they are black. They are not called rubbish bags for nothing!