um, the shell of the lac beetle. Not fatal, you are right. Not even really a beetle. They are a scale insect and they build a shell from body secretions. They discard their shells over and over. and I can't really imagine a happy scale insect, anyway. just an attempt at a little joke...

and, believe it or not, many polyurethanes are reclaimable and recyclable (although most likely not the material that I would place on my handlebar twine). Recycling helps to balance the environmental cost of the material.

But mostly, they don't get trashed at most temperatures that a bicycle would be exposed to, while shellac can melt and get gooey while in your trunk on a hot day.