Cells absolutely produce waste. That's why animals have things like kidneys and livers. Animals also have immune systems to survive mild infections. Cells grow

Cells absolutely produce waste. That's why animals have things like kidneys and livers. Animals also have immune systems to survive mild infections. Cells grown in a lab are much more prone to any form of contamination at all. It's possible to deal with both things in a lab, but not inexpensively.