My wife makes her own dog food out of 1 Lb of rice, 1 Lb of carrots, and the trimmings of 1 whole chicken. After she breaks down the chicken for the meat that the family will eat during the week, all the trimmings, including the bones, are put into a pot and boiled so we get the marrow and gelatin from the bones as well. I'd describe it as making stock except that the liquid is not separated for reasons I'll get back to. Once the 'chicken stew' has cooked, she finds all the bones and puts them into a high-end blender to render into a thick paste we call a 'bone shake'. She puts the rendered bone into the the stew / stock along with the rice and carrots to finish cooking. Once that is done she adds vitamins and other supplements to the batch before dishing out portions for freezing and then we have dog food for several weeks.
We have used everything from the chicken, including the skeleton. We joke that the dog eats better than we do and have had multiple vets give their approval.
Now, for those who ask what this has to do with human food, my response is even though we use this process to feed the dog, there is nothing special about it and would be perfectly safe for humans. The bones are completely rendered in the sense of cook time and safety. Cooking them in the stock makes them safe from a bacteria perspective and using the blender essentially grinds them into particles so small as to eliminate any issues with splintering. In fact, my wife started to make (dog) cookies by adding sugar, flour, salt, etc. I mention this to illustrate the multitude of uses for the bones so there is no reason why the bone shake couldn't be incorporated into other recipes for people.