what do they with excess skin after it remove

I was just wondering what do they with excess skin after it remove I used to weigh over 700lbs and I started to notice some excess skin

It's medical waste unless your plastic surgeon/hospital unit coordinates a living skin donation with your agreement (which I think is pretty rare but I'm not an expert).

IIRC, back when I had my surgery there was some talk on the forum(s) that the skin could be donated to burn victims for grafting .. I never knew anyone personally that did that, though, either on here or in real life ..

the skin removed after weight loss surgery is not usable for skin grafting. Skin for grafting usually comes from a living donor(ones self if possible) because only a small thickness is used.
skin from skin removal surgery is medical waste and usually incinerated.

"It places the lotion on the skin", then throws it in the medical waste garbage :).

or it gets the hose

I think it makes sense to donate it to research. It seems like a waste to throw it out.