During canning season we glean tomato skins and onion peels and ends, dehydrate them, then run them through the food processor to make onion and tomato powder.
I dehydrate celery tops/leaves for use in soups, stews, etc.
When I roast chickens with vegetables I refrigerate the vegetable scraps and hold them. After the first meal we debone both chickens. We put the carcasses and the vegetable scraps along with some herbs, spices, a splash of apple cider vinegar and water into my pressure cooker for two hours to make bone broth. I run the carcasses and scraps through two batches, adding more herbs and spices and a bit of our dehydrated vegetables to the second batch. I combine the broth from both batches to levelize the broth concentration, then pressure can it. That's nearly free food. Look at the price of chicken stock in the grocery store. The remaining chicken carcasses either go right into the crab pot in season or into the freezer in preparation for crab season.