They don't? A 5s google search reveals this document
https://www.fda.gov/files/about%20fda/published/Recycled-Org...
>Recently, State Veterinarians and State Feed Program Managers have been approached by waste management firms that intend to use recycled organic waste from large wholesalers, distributors, and retailers as animal feed
...and this: https://www.epa.gov/sustainable-management-food/reduce-waste...