More on rendering, or Soylent Green
"Meat rendering plants process animal by-product materials for the production of tallow, grease, and high-protein meat and bone meal. Plants that operate in conjunction with animal slaughterhouses or poultry processing plants are called integrated rendering plants. Plants that collect their raw materials from a variety of offsite sources are called independent rendering plants. Independent plants obtain animal by-product materials, including grease, blood, feathers, offal, and entire animal carcasses, from the following sources: butcher shops, supermarkets, restaurants, fast-food chains, poultry processors, slaughterhouses, farms, ranches, feedlots, and animal shelters."
We didn't really need the EPA to confirm it as plenty of rendering plants have done so on the record and in the press, but it's interesting to see confirmation from a government agency that they're well aware of it.
More on the document and a list of ingredients that you never, ever want to see in your pet's food can be found at The Truth About Pet Food.