Which organ breaks down red blood cell?

The spleen breaks down old red blood cells. The contained hemoglobin is released, which is further broken to globin, a protein and heme, a porphyrin.

The heme is converted to bilirubin, which moves from the spleen to the liver attached to albumin. (Both feces and urine get their color from the products of the breakdown of the heme.) The iron recycled from the breakdown of the heme group is stored in the liver.