The Unsung Hero of Agriculture: Why Rendering Matters
If you ask most people if they can explain the concept of rendering, most will probably say no. But according to Dr. Charles Starkey of the North American Renderers Association (NARA), the concept is something most people actually have familiarity with—often in their own kitchens.
“Rendering is really dehydration,” Starkey explains. “If you fry bacon or cook a turkey and see it bubbling, that’s the water escaping from the tissues as the fat heats up. That’s essentially what we do—just on a larger scale.”
In simple terms, rendering uses heat to remove moisture from animal materials, stabilizing them and eliminating harmful bacteria or viruses. The process transforms what would otherwise be waste into valuable ingredients such as animal proteins and fats used in animal feed, pet food, fertilizers, and even industrial products, that are used all over the world. And that process, although mostly unknown by the general population, has big ramifications for sustainability in animal agriculture and beyond.
How does rendering work?
Starkey points out that in North America, consumers typically eat only about half of an animal. The rest—organs, bones, fat, and other co-products—often go unused. Rendering ensures these materials don’t go to waste.
“We process the parts of the animal that you and I choose not to eat,” Starkey says. “And we turn them into useful products.”
The industry often refers to itself as “the original recyclers.” For centuries, animal fats have been repurposed into everyday products such as soaps and candles. Today, the process has expanded into a sophisticated system that supports modern agriculture and environmental sustainability. By rendering the unused parts of an animal, rendering helps grow the next generation of food by recycling unwanted meat into new and clean ingredients for products.
Rendering works like this: animal leftovers (scraps, bones, etc.) and oils are collected from places like packing plants, grocery stores and restaurants. During the rendering process they are ground into a uniform size, cooked to separate fat and protein and to kill any bacteria. Fat is then purified by centrifuge while the protein is further ground up. Fully rendered ingredients can be used to produce products such as biofuel, pet food, livestock feed, aquaculture feed, fertilizer, personal care items like soap and deodorant, as well as industrial products like leather or paint.
“There's nobody that recycles better and more fully than renderers,” Director of the CLEAR Center, Dr. Frank Mitloehner said. “Everything but the moo and oink is recycled. From hides to hair, from organs to claws, from fats to proteins. There's nothing wasted when you slaughter an animal or when an animal dies. Renderers are the absolute perfect recyclers.”
And without rendering, the planet would look a lot different than it does now. Millions of tons of organic material would need to be disposed of each year. If that material ended up in landfills, Starkey says, those landfills could fill up in just a few years. Even more concerning is what would happen as that waste decomposed in the landfills
“As it breaks down, you get greenhouse gases like methane, ammonia, and sulfur gases,” Starkey explained.
When wasted food goes to a landfill, the nutrients in the food never return to the soil. The wasted food rots and produces methane, a greenhouse gas 28 times as powerful as carbon dioxide at trapping heat in the atmosphere. The Environmental Protection Agency (EPA) estimates that wasted food is responsible for 58% of landfill methane emissions to the atmosphere. Simply put: tackling food waste offers us a critical opportunity to address climate change by reducing methane emissions.
Rendering prevents those emissions by stabilizing the material and repurposing it into useful products—making the industry a key player in what scientists call the circular economy, where resources are reduced, reused and recycled rather than discarded.
Animal rendering and pet food: How coproducts become ingredients
Starkey’s work in rendering is closely connected to his background in animal nutrition and the pet food and feed industries. Starkey studied at Arkansas State University before earning his Ph.D. in animal nutrition from Kansas State University. Today, he not only serves as Vice President of Scientific and Regulatory Affairs at North American Renderers Association, but he also leads research efforts as Director of Research for the Fats and Proteins Research Foundation. Before joining NARA, Starkey was an assistant professor in Auburn University’s Poultry Science Department, where he taught courses in animal feed manufacturing and poultry production. His research focused on pet food and feed manufacturing, and animal nutrition—experience that now informs his work advancing the science behind rendered ingredients used in animal diets.
During the rendering process, materials that are not eaten by people, but are safe and nutritious for animals, are collected from meat processing facilities. Co-products (or some refer to them as by-products) such as tallow, fatty acids, amino acids, deboned meat remnants, as well as animal livers, are carefully inspected and processed to create animal feed ingredients.
At rendering plants, these materials are quickly heated at high temperatures, a process that destroys bacteria and pathogens. The resulting protein meats and fats are then stored and handled under controlled conditions to ensure safety and quality. All rendering plants are in compliance with FDA’s animal food regulations under the Food Safety Modernization Act (FSMA). In addition, renderers have quality and safety control systems in place via formal programs such as the Rendering Industry Code of Practice.
Data from Decision Innovation Solutions estimates that pet food manufacturers use about 3.8 million tons of animal-based ingredients each year, along with4 million tons of grains, soy products, fruits, and vegetables, and roughly 200,000 tons of seafood products. Rendering safely transforms these materials into nutritious feed and pet food ingredients, helping reduce food waste while providing the nutrition animals need.
Protecting animal, human, and environmental health
Starkey says rendering also plays a critical role in public health.
Through high-temperature processing, harmful pathogens are destroyed, reducing the risk of disease spreading through decomposing animal materials. This connects rendering to the concept of One Health, a global approach recognizing that human health, animal health, and environmental health are interconnected.
“If we had to pile these materials up somewhere or send them to landfills, there would be a much higher potential for disease spread,” Starkey says. “By processing them safely, we help protect both animal and human health.”
The industry takes safety very seriously. Through programs coordinated by NARA and the Animal Protein Producers Industry (APPI), rendering facilities voluntarily participate in microbial testing programs to monitor for pathogens and ensure the safety of products used in animal feed and pet food. Training programs also educate plant operators, quality assurance professionals, and feed manufacturers on best practices for safety and operational excellence. And they’ve recently opened these workshops up to those in the pet food industry as well, as a resource to learn more about the rendering process.
Producing clean water
Another surprising benefit of rendering is something many people probably wouldn’t associate with the industry: water production.
The materials processed in rendering facilities contain a significant amount of moisture—often about 70 percent. During the dehydration process, that water is removed, treated, and returned to the environment.
“In North America alone, rendering facilities recover and treat roughly 3.7 billion gallons of water that would otherwise be wasted,” Starkey said. “That water is reclaimed during rendering, cleaned, and put back into the environment as clean water.”
Green energy: Fueling the future
Rendering products are also becoming increasingly important in renewable energy.
Rendering can turn animal co-products into valuable feedstocks for low-carbon fuels like biodiesel, renewable diesel, and sustainable aviation fuel. These fuels play an important role in cutting greenhouse gas emissions today — especially in industries that can’t easily switch to electric power.
A considerable percentage of America’s biodiesel and renewable diesel is made from unused cooking oil, also known as UCO, such as that used in fryers, with a large amount also coming from animal fats. In fact, roughly 18-20 percent of the feedstock used to make these biofuels comes from fats and oils supplied by the rendering industry. Because of their chemical composition, fats release concentrated amounts of energy when burned which can be used as a biofuel.
Starkey added that they are continuing to do research to better understand how they can optimize rendered products for use in the conversion into renewable fuel sources.
Rendering: A quiet, but essential industry
Despite its massive environmental and agricultural impact, rendering remains largely invisible to most of the general public.
“We’ve been a pretty silent industry over the years,” Starkey said. “But we’re trying to change that.”
Part of the lack of knowledge about rendering is historical. Older rendering facilities sometimes had odor issues which shaped public perceptions. Modern plants, however, use advanced technologies to capture and treat emissions, preventing odors from leaving the facility.
Still, awareness remains low. Starkey pointed out that, “if one was to do a quick internet search of the word ‘rendering’ it often brings up artistic renderings and representations, so people don’t even understand what the word refers to.”
Yet the industry has been operating for centuries and continues to evolve alongside modern sustainability goals.
“We’ve been doing it on industrial scale for two centuries now,” Starkey pointed out. “When you look at global sustainability goals and the circular economy, rendering fits into so many of those areas.”
From preventing food waste and protecting public health to producing renewable fuel, rendering quietly, but effectively supports the entire agricultural system.
“This industry is totally unknown to the public,” Dr. Mitloehner said. “But they have such an incredible story to tell. They are one of the world's best kept secrets. And they shouldn’t be.”