Bio-Meat: Nectar

Bio-Meat: Nectar is a completed series published in Shounen Champion magazine by Fujisawa Yuki.

Plot
Man is having a hard time finding food and getting rid of their trash, so science comes up with a bio-engineered animal that survives by eating trash, and is then killed to feed humanity. But the self-replicating, endlessly hungry killing machine gets loose in Tokyo.