Engineering and Poultry Science Researchers Recover Waste Fat in Poultry Processing Wastewater for Use as an On-Site Alternative Fuel Source

Summary

Research was conducted to show feasibility of waste fat recovery from wastewater for use as an alternative fuel on-site at poultry processing plants.

Situation

Waste fat, oil and grease (FOG) are major components of many food processing wastewater streams. In Georgia, poultry processors are the most prevalent producers of these high FOG wastewaters. In 2006, Georgia poultry processors slaughtered over 1.3 billion broilers (~14% of total U.S. production) and generated approximately 9 billion gallons of highly concentrated FOG wastewater in the process. Presently, most waste chicken fat from poultry processing plants is sold to rendering facilities at relatively low prices. This current method provides an easy way of handling the disposal of waste FOG, but neglects the fact that animal fat is a valuable by-product of the poultry processing industry and has great potential as a source of alternative fuel. The recovery of FOG from poultry processing wastewater without the intensive use of heat energy is very attractive as has the potential to recover a substantial portion of the 44.6 million gallons of waste FOG leaving poultry processing facilities in the state of Georgia annually. Offal is generally sold to rendering facilities at ~$0.07/kg (~$0.03/lb). This gives the fat a value of $0.24/gal as it is presently handled. Purified fat from poultry processing wastewater can be used as a boiler fuel on-site displacing fuel oil, which is currently valued in excess of $2.00/gal. Using the conservative estimate of only recovering 25% of the 44.6million gallons of fat produced in the state each year by this method would result in an estimated savings of nearly $20 million/year.

Response

University of Georgia researchers in Poultry Science and Biological & Agricultural Engineering, with funding through the Georgia Food Processing Advisory Council (FoodPAC), evaluated five (5) waste fat raw materials recovered from poultry processing wastewater as potential sources of alternative fuel. Three (3) major poultry integrators (Pilgrim's Pride, Gold Kist, Harrison Poultry) partnered with UGA allowing researchers access to processing plant wastewater treatment areas for sample collection. The raw waste fat materials included float fat recovered after primary offal screens, secondary screen offal, tertiary screen offal, and chemical and non-chemical DAF skimmings. Each raw material fat source was subjected to low-temperature heating (54oC, 130oF) to liquefy the free fat. The liquefied fat was then separated from the solids through pressing, and further purification accomplished through centrifugation. The resulting purified fat samples were analyzed by the University of Georgia Biofuel Testing Laboratory for energy content, specific gravity, dynamic viscosity and ultimate elemental analysis. Prepared sub-samples were also analyzed for triglyceride profile, moisture, insolubles, unsaponifiables and free fatty acids. The recovered poultry fat samples were also combusted in the Clean Burn CB 350 CTB boiler. Engineering data was collected on the performance of each fat sample. Stack emissions were measured for oxygen, carbon monoxide, carbon dioxide, combustible gases, excess air, nitric oxide, nitrogen dioxide, NOx (NO + NO2), and sulfur dioxide. Results of waste fat fuel-quality and combustion analysis were compared to common petroleum fuels for comparison.

Impact

Of the five (5) waste fat sources analyzed, float fat and secondary screen offal showed the greatest potential impact in terms of ease of extraction and recovery efficiency. The average volume of purified fat recovered from 100 kg of raw float fat was 18 kg (5.3 gallons), while secondary screen offal yielded an average of 16 kg (4.7 gallons). Currently, poultry processors could expect to receive ~$7.00 from the sale of 100 kg of float fat or secondary screen offal to a renderer. However, that same 100 kg of float fat or secondary screen offal can produce ~5.0 gallons of purified fat worth in excess of $2.00/gallon or a minimum of $10.00/100 kg of raw material. Isolating the free fat in either the float fat or secondary offal waste streams can result in the recovery of 1,500 – 2,000 gallons of purified fat each day in a poultry processing plant, displacing $3,000 - $4,000 currently spent on petroleum based fuel oil. Performance of the poultry fat fuels was near that of the petroleum based fuels. The average consumption of poultry fat was (2.22gal/hr) very close to that of ultra-low sulfur diesel (2.17gal/hr). ?T, which is the difference in temperature between incoming water and outgoing water, was comparable between poultry fat (22.78oF) and diesel fuel (20.88oF). Diesel fuel and poultry fat had almost identical efficiencies of 78% and 79% respectively. Overall the FOG based fuels preformed as excellent fuel oil replacements in this recycled oil fueled boiler system. This initial work by UGA has shown that the collection, extraction and purification of concentrated-fat from poultry processing wastewater is a feasible method of providing a product that can be an alternative to petroleum based #2 fuel oil for industrial boilers. Along with providing reduced fueling costs, this work could increase domestic energy security by displacing foreign petroleum with domestic poultry fat. Additionally, since this material is actually produced in the state of Georgia, it takes advantage of Georgia's own energy resources. Finally, since this material is used in-house it eliminates transportation costs and conserves the fuel necessary to transport petroleum products to poultry processing facilities where the fuels are needed. Based on these initial results, the research team has received funding to collaborate on the design and development of a self-contained low-temperature fat extraction and purification unit that can be installed on-site at poultry processing plants to produce a usable quantity of fuel-quality fat in an economical manner. It is conceivable that with a full-scale version of this system, a poultry processor could be washing and cleaning both birds and equipment with water heated by boilers fed waste fat recovered from birds processed earlier that same day.

State Issue

Agribusiness Development/Value Added

Details

• Year: 2007
• Geographic Scope: National
• County: Clarke
• Program Areas:
  • Agriculture & Natural Resources