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bioweb.sungrant.org » Technical » Biomass Resources » Agricultural Resources » Processing and Food Wastes » Waste Grease and Fats

Waste Grease and Fats	Printer Friendly

Waste fats, greases, and oils are currently used to produce a number of industrial products including soap, lubricants, and biodiesel, although the majority of these wastes are used in livestock feed. Approximately 49% of the live weight of cattle, 44% of the live weight of pigs, 37% of the live weight of broiler chickens and 57% of the live weight of fish are composed of materials not consumed by humans. These materials include hides, skin, bone, feathers, organs, whole carcasses, etc. About 54 billion pounds of these materials are generated annually in the U.S., with about 60% of the weight being water, 20% protein and minerals, and 20% fat. Many of these products undergo further processing (called rendering) to make them useful for other products (Meeker, 2006).    About 4.23 million metric tons (9.3 billion pounds) of fats and greases (inedible tallow, yellow grease, other grease, edible tallow, lard, and poultry fat) are processed by the rendering industry annually (table 1). Tallow (fat that solidifies at around 40-45°C) is primarily derived from rendered beef tissue, but can contain fat from other animals. Lard is derived from hogs. Yellow grease is the waste cooking fats and oils produced by the restaurant industry. Much of this grease is collected and recycled by the rendering industry, which estimates that an additional one billion pounds of fats are used in pet food and are not accounted for in the official statistics. Additionally, while an established infrastructure exists to collect yellow grease and trap grease in metropolitan areas, this infrastructure may not be as well developed in rural areas and thus total quantities may be underestimated (Groschen, 2002).   In addition to yellow grease, restaurants also produce trap grease. Trap grease is restaurant cooking fats and oil that are lost down the sink drain and captured in grease traps. Some trap grease is collected and recycled by the rendering industry, but much of it is collected by septic tank services for disposal, or escapes the trap and is flushed into municipal sewage systems (Wiltsee, 1998). Tyson (2004) estimates that 3.81 billion pounds of trap grease are produced annually.   Around 42% of the fats and grease processed by rendering industry are used domestically, primarily for livestock feed (about 85%) with the remainder used for industrial products. In addition to domestic use, a significant quantity of rendered fats and greases are exported.   Compared to virgin vegetable oil (such as soybean oil), waste greases and fats are lower priced. The spot market price for yellow grease (as of February 2, 2007) was $18.75/hundred weight and $20.00/hundred weight for inedible tallow and $23.00/hundred weight for edible tallow (USDA).   Tallow, lard and poultry fat are by-products of the meat industry and future supplies depend on demand for meat, milk, and eggs. Yellow and trap grease are by-products of the restaurant industry and institutional uses (such as school cafeterias) and future quantities depend principally on demand for food away from home. Wiltsee (1998) collected data for yellow grease and trapped grease in 30 randomly selected metropolitan cities in the U.S. and estimated their per capita production. The per capita production of yellow grease ranged from 3 to 21 lbs/person/yr and averaged 8.87 lbs/person/yr and for trap grease, per capita production ranged from 4.8 to 26.6 lbs/person/yr and averaged 13.37 lbs/person/yr.

References
Groschen, Ralph, Overview of the feasibility of biodiesel from waste/recycled greases and animal fats, Minnesota Department of Agriculture, Marketing Services Division, October 2002. Meeker, David L., and C.R. Hamilton, September 2006, An overview of the rendering industry, in Essential Rendering: All about the animal by-products industry, David L. Meeker (editor), Kirby Lithographic Company, Inc., Arlington, VA (publishers), pp. 1-16, www.renderers.org. National Renderers Association, www.renderers.org. Tyson, K. Shaine, Joseph Bozell, Robert Wallace, Eugene Petersen, and Luc Moens, Biomass oil analysis: research needs and recommendations, National Renewable Energy Laboratory, NREL/TP-510-34796, June 2004. Wiltsee, G., November 1998, Urban waste grease resources assessment, NREL/SR-570-26141 U.S. Department of Agriculture, Agriculture Online, www.agriculture.com.