Humans grow vegetable matter. Eat part of it. Compost the rest and use that to help grow more vegetable matter. One use of inedibles involves pressing and producing useful container shapes. In our home, we use one of the larger form factor plants to heat the interior. Cellulose, fiber from any variety of plants, all are useful.
Gluten-free? Give me a break from silly marketing, from hustling people. Please!