Rendering is the process of melting down animal tissues and fats into usable final products. This process in conducted on a large scale to meet the need for fats and tallow for several leading global industries such as cosmetics, cleaning chemicals, pharmaceuticals, oils, animal feed, candles, and bio-diesel, to name a few.
The process of rendering requires the animal tissues to be finely chopped or ground and then melted down using medium to high heat. For non-edible rendering, the tissue is heated in a steam-jacketed vessel which removes moisture from the product. When the moisture is removed the fat is released from the cells where it melts down into a drain and is collected for use. The remaining tissue is then pressed so any remaining fat can be dredged out of the material. The fat-less remains are then ground up and used to make meat and bone meals.
For edible rendering, the finely chopped or ground tissue is heated continuously at a low (below boiling point) temperature for a long duration of time. The heated and processed material is then subjected to two or more centrifugal separation processes. The first application of centrifugation removes the fat and water from the tissues while the second application removes the water from the fat. This process of rendering is most commonly done in the meat packing and processing industry. Think sausage and hot dogs.
History of the Industry:
The process of rendering animal fats has been around for thousands of years. The first candles and oils were all made of rendered animal fats. Commercial rendering and trade started in the 1800s with the growing popularity of tallow, soaps, glues, and candle making materials. Animal fat was one of the most valuable commodities in that time with the fat of an animal selling for nearly double the price of the meat or pelt. A preference for imported alternative fats, such as coconut oil and palm oil, caused the demand for domestically rendered animal fats drop around the time of the Great Depression threatening the entire industry. Because of this, industry leaders organized and formed the American Producers of Domestic Inedible Fats in 1933. This organization later became the National Renderers Association (NRA).
One of the first actions taken by the American Producers of Domestic Inedible Fats was to lobby the United States government to impose a fats and oils excise tax which they managed to do successfully. This tax did not aim to limit the amount of foreign fats being imported, but to even the pricing between foreign and domestic products. This tax was imposed and written into the Revenue Act of 1934. Following this, domestic sales of rendered products sky-rocketed. But in the 1950’s, manufacturers started producing detergents with petrochemicals and the demand for rendered fats plummeted. With a 50-70% drop in price and value in the domestic market, the industry started to look outside of the US for beef tallow demand, focusing on marketing their product globally. By 1953, between a third and a half of all rendered fats in the United States were exported, and by 1956, exporting made up for market lost to petrochemicals. The year 1956 was also when the National Rendering Association entered into a cooperative agreement with the U.S. Department of Foreign Agricultural Service (FAS) to jointly fund international marketing activities for animal fats and greases. This agreement remains intact today and continues to promote industrial demand for tallow from soap and cosmetic companies and the fatty acid chemical industry through technical and marketing seminars and promotional literature. In addition to domestic push, the NRA also enacted global soap and hygiene industry programs in countries like Korea, Turkey, Taiwan, and Japan to encourage wider use of soap and cosmetic products, thus increasing demand in these countries.
As a whole, it is widely felt that the rendering industry plays a large and positive role environmentally, by significantly reducing waste deposited into landfills and waste processing facilities. Deceased animals that would have previously been left to rot, potentially contaminating the ground water, are removed and their byproducts processed and used. This re-purposing of waste also greatly reduces the amount of methane emitted from landfills, which is considered a major greenhouse gas.
However, the process of rendering can best be compared to cooking. When you cook a meat product, it emits an odor. In the case of rendering facilities, these odors are often unpleasant, and often contain VOCs from the process itself. Government agencies, like the EPA, started regulating the emission of odors from rendering facilities in the 1960’s, but really cracked down on the industry in 1990, in the Clean Air Act Amendments of 1990. This amendment came after several requests from the industry on clarification regarding odor thresholds that were not previously made known. The EPA considers odor emitted from rendering facilities as a nuisance odor and states:
“A person shall not discharge, cause, suffer, allow, or permit from any source whatsoever
such quantities of air contaminants or other material which will cause injury, detriment,
nuisance or annoyance to any considerable number of people or to the public or which
endangers the comfort, repose, health or safety of any such persons or the public or which
causes or has a natural tendency to cause injury or damage to business or property.”
-ENVIRONMENTAL PROTECTION REGULATIONS, CHAPTER 5
In addition to the EPA, rendering facilities must adhere to their state and local regulatory agencies, as well as the local environmental impact groups and citizens. Because of this, odor control regulations for rendering can be complicated and often change. Groups like the National Rendering Association and the National Meat Institute are heavily relied on to provide up-to-date knowledge on regulations and provide support in finding pollution control equipment.
Some of the harshest pollution control applications are in the rendering field of the food processing industry. The waste stream can contain odors, ammonia, fats, grease, water and other vapors, and even particulate matter, all in a wide-ranging mix. GCES custom designs systems to handle these difficult processes based on each facilities waste output and goals. GCES has a long history of experience providing odor control solutions to the rendering industry. Our very first piece of equipment was installed in a rendering facility and that customer has continued to come back to us over the years. This is because of our extensive knowledge of the rendering process and our commitment to building durable solutions.
Although GCES provides custom designed technology for each application, the most commonly used type of equipment in the rendering industry is a Regenerative Thermal Oxidizer. This type of oxidizer uses extremely high heat, about 1500°F, to clean the exhaust of dangerous pollutants and compounds. Developed for large volumes and low VOC concentration air pollution applications, Regenerative Thermal Oxidizer (RTO) technology is based on using ceramic media as heat recovery exchangers and switching values. This design contrasts with Thermal Recuperative Oxidizers which use metallic shell and tube heat exchanger technology with primary and/or secondary heat. In this configuration, among other distinctions, the outgoing clean process stream of a secondary heat exchanger process can be routed to another part of the plant for its use or back to the process itself.
If not properly designed a RTO can experience issues in a rendering application. Due to the number of condensable organics and wastewater being emitted from the cooker, a residual layer of fats, grease, and oils will build up on the ductwork, valves, and inlet ceramic media of an improperly designed RTO unit. Over time, this buildup will create conditions of flammability in the RTO. To mitigate the risk of fire, a “bake-out” cycle is used to remove such buildup in a controlled manner during a preset schedule. A bake-out cycle revolves around varying the timing of the inlet and outlet valves and using the heat in the RTO to dry and incinerate the residue to ash. Due to the high temperature exposure of bake-out cycles and the acidic and moisture/vapor-laden nature of the incoming exhaust stream, stainless steel is used to fabricate the cold condensable areas of the RTO unit. The incoming ductwork, valves, ceramic media supports, outlet ductwork, fan, and exhaust stack that are exposed to the condensable liquids and corrosive elements of the air stream; these components are manufactured from stainless steel or other corrosion resistant alloys (CRA).
An Aqueous RTO is a specialized RTO, that excels in rendering applications. Vapor-rich and wastewater waste streams, such as those from the rendering process, can pose challenges for traditional treatment systems. The configuration of this RTO is the same as a traditional setup, but with added liquid capabilities. This consists of pumps, mixing and storage tanks as needed, spray/injection nozzles and associated piping and controls. This system provides controlled injection and processing of the water into the inlet stream for dispensation through the oxidizer, using heat from the combustion chamber to help vaporize the fluid. Automatically synchronizing air flow, water pressure and flow, process temperature and pressure provides steady and reliable operation.
GCES’ extensive experience in the rendering industry has positioned us as one of the top odor control solution providers in the industry. Our unique approach is to analyze your process stream and business objectives from which we propose an ideal solution or range of options to help achieve and optimize those objectives. If you have questions about a rendering project, or any of our equipment, please email us at firstname.lastname@example.org.