Collegen casings are not really made from byproducts, they are made from the layer of collegen between the hide & the fat.
I've never been a pure vegetarian. even when I did not eat meat, I still consumed dairy products. Right now, I do eat meat but not a lot of it. I am still not comfortable handling raw meat as I still have difficult blocking out the thought that I am supporting an industry that is inhumane. Morally, I am not against eating meat, just against the way animals are treated. I have a friend who visited abbatoirs and became a vegetarian overnight.
OK, I hope I am not out of line saying that but I think everyone already knows the situation. In any case, as I said, I do eat some meat. I don't, however, go near any kind of offal, at least for myself. I buy it occasionally for my dog who loves it.
The idea of collagen casings is something I am pleased to learn about.
One thing I do like to use meat for is hamburgers. I use a mixture of minced meat and mashed vegetables but it always falls apart!
If anyone knows how to keep a meat patty totally intact when cooking... I WANNA HEAR ABOUT IT!! (I used egg to bind the ingredients but it is not working for me!)