Rendering

Rendering is a process that allows typically unusable parts of animals to be ‘recycled’ into useful materials, providing continued economic value and reduced environmental impact. In the rendering process, parts of an animal carcass are cooked at specific heats, pressures, and temperatures, producing high-protein solids, fats, and water. These materials can be used to make many products, including animal feeds, soaps, fuels, and more. Rendering can be performed commercially or on a small scale.

Although animal carcasses are often thought of as unsanitary, the rendering process typically makes products that are safe, as rendering removes most germs and smells. Still, if an animal carcass will be rendered, it should be kept cool, and rendering should take place within 24-48 hours of the animal’s death. There are several methods of rendering. It can be ‘dry’ or ‘wet’ and is performed at different temperatures and pressures depending on the carcass specifics. All methods often take several hours to fully break down a carcass. 

The end products from rendering can be used in many applications: food for livestock, pets, poultry, and aquaculture; in the chemical industry; for fertilizer; as fuel; and for soaps, personal care products, pharmaceuticals, and cosmetics. The quality of rendered products, and therefore what they can be used for, depends on the quality of the carcasses and how they were processed. Different species of animals produce rendered products with different proportions of fat, high-protein solids, and water. For example, cattle typically produce about 10% fat, while sheep produce about 20% fat, and swine 30%. 

Some animals, primarily cattle, sheep, goats, and deer, are at a higher risk of carrying a disease known as transmissible spongiform encephalopathy (TSE). TSE is an untreatable, fatal brain disease that can infect multiple species, including humans, if food containing infectious material is eaten. Strict testing and tracking protocols have greatly reduced the risk of TSE in many farmed animals, however, TSE in deer populations has been spreading. Rendering may not completely eliminate the risk of transmitting this disease, so in an effort to prevent it, federal regulations require animal feed made from specific rendered materials to be labeled and tested. Before these requirements came into effect, many animals died from TSE transmission from contaminated food made from rendered products. In further efforts to prevent TSE spread, rendered tallow (fat) should contain a maximum of 0.15% insoluble impurities, as the impurities may contain infectious material. 

Laws Surrounding Animal Carcass Use

Carcasses may be sourced from agricultural production, hunting, or sometimes, roadkill. West Virginia allows individuals to possess roadkill if an individual notifies a law enforcement agency within 12 hours and acquires a non-hunting game tag within 24 hours. For safety, it is recommended that carcasses of unknown origin or time of death not be used to produce edible products. 

If an individual renders a carcass to produce other products, two common products are pet foods or tallow-based personal care products. Specific permits and licences may be required based on the specifics of an individual business. For example, selling products out-of-state requires compliance with interstate commerce regulations, and the West Virginia Department of Agriculture requires registration of businesses producing pet food. Soaps and other personal care products are a common option to make with rendered fats. Federal regulations classifying a product as a soap, cosmetic, or drug are stringent (see table). West Virginia uses these federal regulations as guidance for soaps and other products that may be made from the fat of rendered animals, and specifies that the products cannot be adulterated. Pennsylvania provides additional guidance on rendering products that will be eaten or used in cooking.