Millions of tons of animal by-products are produced in the U.S. each year in the agricultural and animal industries. The rendering process allows for the recycling of animal slaughtering wastes that would otherwise be disposed of in landfills.

Savannah Cooper


The animal processing industry provides meat, eggs and milk to stores—and thus to people—around the world. But many of the by-products of this industry are not suitable for human consumption. The large amounts of waste from the animal agriculture industry could fill landfills to capacity and wreak havoc on the environment’s delicate balance. Fortunately, though, these by-products can be recycled into meal and used in the production of animal feed to supply additional nutrients to livestock, poultry and even pets.


Waste By-Products

Bone meal is a mixture of finely and coarsely ground slaughterhouse waste products. The most common sources of these waste by-products are beef, pork, sheep and poultry. This mixture can be used as an organic fertilizer for plants or as a nutritional supplement for livestock and other animals. The use of bone meal in livestock feed can even prevent “mad cow disease.”


Similarly, meat meal is an animal feed produced by recycling animal by-products. These by-products are cooked, or “rendered,” to produce a nutritional and economical feed ingredient. When bones are added to meat meal, it becomes a product known as meat and bone meal (MBM). MBM is an excellent source of protein, calcium phosphorous, vitamin B-12 and numerous other minerals that are necessary to an animal’s health.


Rendering Process

In order for animal by-products to be used in other materials and processes, the by-products must first be treated. Bone meal, meat meal and blood meal are produced in a process known as rendering. In this process, the raw material is heated to remove moisture and release fat. The dry rendering process often begins with crushing and grinding the material, followed by heat treatment to reduce moisture content and eliminate any microorganisms. The melted fat is then separated from the solid protein through draining and pressing, and the solid material is ground into powder, such as meat meal, meat and bone meal, feather meal and blood meal.


The rendering process transforms waste by-products from the animal industry into stable, valuable and safe-to-use materials. The majority of the waste material that is processed in rendering comes from slaughterhouses and can include fatty tissue, bones and other processing offal. Offal is the parts of an animal that are not fit for human consumption, such as organs, blood and feathers. Almost 30 percent of an animal’s live weight ends up as offal, which would be expensive to dispose of and wasted if not for the rendering process.


In the rendering process, the inedible parts of slaughtered livestock are transported to a rendering plant, where the material is ground, cooked and pressed into meat and bone meal. The different grades of meal are blended back into poultry and slime feeds, as are the fats from the process. There are 3,600 calories per pound of fat, making the material valuable for adding energy to the feed. A rotary dryer is often used in the process to remove moisture from the raw material. In addition to producing meat and bone meal, a rotary dryer can also be used to coagulate and dry blood for blood meal and to produce feather meal, which can be used as a feed ingredient.


Making Useful Product

There are approximately 300 rendering facilities in North America that serve the animal industries by using the by-products of animal processing. The U.S. alone currently produces, slaughters and processes about 100 million hogs, 35 million cattle and eight million chickens every year. Altogether, the by-products from these processes amount to more than half of the total volume produced by animal agriculture in the production of meat, milk and eggs for human consumption.


Anywhere from one-third to one-half of each animal produced for meat, milk, eggs and fiber is not consumed by humans. About 49 percent of the live weight of cattle, 44 percent of the live weight of pigs, 37 percent of the live weight of broilers and 57 percent of the live weight of most fish species are materials that are not consumed by humans.  The current volume of raw material generated each year is nearly 54 billion pounds.


When these raw waste materials are subjected to the rendering process, the result is many valuable and useful products, from bone meal to poultry meal, which are then used as feed ingredients for cattle, poultry and pets.


The composition requirements for MBM and all other meals and animal feed ingredients used in the U.S. are established and regulated by the Association of American Feed Control Officials (AAFCO). MBM, for example, must contain a minimum of four percent phosphorous with a calcium level not to exceed 2.2 times the actual phosphorous level.


Millions of tons of animal by-products are produced in the U.S. each year in the agricultural and animal industries. If these waste products are not recycled or reused, they must be disposed of in landfills, causing huge economic losses for the animal processing industries, as well as issues in the environment. Meat and bone meal and blood meal are valuable products that can be sold for use in the pet food industry, feed industry and other industries. The fats from the rendering process can also be used in the pharmaceutical, chemical and oil industries, as well as many others.


The rendering process allows for the recycling of animal slaughtering wastes that would otherwise be disposed of in landfills. These recycled products can then be used in animal feed or as organic fertilizers. Recycling these waste materials is not only beneficial for the environment; it also prevents substantial loss of money for those in the animal agriculture industries. Making meal from raw waste materials is an economically beneficial process that produces valuable products for the agricultural industries.


Savannah Cooper is a Writer/Copy/Social Media Specialist at Worldwide Recycling Equipment Sales, LLC. For more information call (660) 263-7575 or visit