What the Shell!?!

So for all of these years from reading household tips here and there INCLUDING a well-known home network, I have read that putting your egg shells down the disposal either cleaned/aided a faltering disposal and/or sharpened the blades. All these years here I thought I was doing an innocent task of throwing my little shells down the drain and chopped those bad boys in the disposal was helping and not creating problems ...

So we had a friend of ours visit recently who works in the water waste treatment industry and has informed me that I should NOT put those shells in the disposal. I should put them in the trash as well as coffee grounds (or for you compost types, you know what to do). I don't know the exact reasons why, but supposed the egg shells don't break down as they need to happen.

I knew coffee grinds were not good for the drain as well as potatoes, but now I happily add egg shells to my list.

Don't believe me google: egg+shells+disposal
I don't know all the literal reasons WHy it is bad to do, I just trust my buddy it is as he is in the industry and he seemed pretty passionate about it. SO I am running with it. Typically I ask TOO many questions, but I knew we were heading in a chemical and processing issue direction and at that point I took his word for it.

I hear the egg shell remedy often so I thought sharing this info may help you too! Help the waste water people out (they have enough &*^% on their plate-pun intended)