Tl;dr - that black liquid is tar collected from smokers' "donated" lungs
A health NGO in Thailand has made a video that should make smokers want to give up tobacco forever.
The Thai Health Promotion Foundation, along with experts from the faculty of medicine at Chulalongkorn University and advertising agency BBDO, created the "Message from the Lungs" using tar that was collected from smokers' "donated" lungs and turned into ink.
[We] successfully extracted black substance from smokers’ donated lungs and made it into ink.
Then bottled and distributed them in public space for people, especially current and potential smokers to see how smoking can harm their lungs and their bodies, and also convince them to quit sooner.
If the gruesome thought of the remnants of your lungs being turned into ink doesn't make you want to quit smoking then we're not quite sure what will.