Managers of the rendering processes at American Proteins in Cuthbert, Ga., like to say that by the time they process the byproducts like feathers, bones, blood and viscera from over 13 million birds per day received at their plant they have extracted everything but the chickens’ cluck.
American Proteins utilizes the best available rendering technologies to process poultry offal into products with value, turning disposal costs into a revenue source for processors. In fact, in recognition of its outstanding performance in wastewater treatment and overall commitment to environmental stewardship, the Cuthbert rendering facility received U.S. Poultry & Egg Association’s 2012 Clean Water Award for a full-treatment facility.
The Cuthbert rendering plant is not the company’s largest, but the number of chickens slaughtered by the processing facilities it services represents about eight percent of total U.S. broiler slaughter.
High volume brings with it economies of scale in processing, but it also brings the potential for big problems with odor and nutrient loading of wastewater. Managing the processes to prevent any environmental insult and keeping neighbors happy requires skill, technology and lots of energy. At the Cuthbert plant, water, energy, protein and fat are recovered and are either sold or put back to work in the rendering facility; nothing goes to waste.
It takes a lot of energy to thermally treat and remove the water from the 2,700 tons per day of chicken byproduct meal and 1,500 tons per week each or pet food-grade meal and fat that are produced at Cuthbert. For instance, the natural gas bill to run the plant’s five cooker lines can run over $1 million per month.
To reduce odor, greenhouse gas emissions and to lower the natural gas bill, the Cuthbert plant has covered its anaerobic lagoon and collects and burns the biogas produced in the lagoon in its boilers. When natural gas prices were at their highest level, the plant saved around $100,000 a month by burning about 1.5 million cubic feet per week of biogas.
Thermal energy is recaptured from the rendering process in a number of ways at the Cuthbert plant. Offals are around 65 percent water, and thermal energy is used to evaporate water out of the byproducts. The water vapor is condensed out of the exhaust and treated to remove nutrients. The condensate is 130-140 F, and this water can be put into either the aerobic or anaerobic lagoon in the winter months to warm the bacteria up. A higher temperature in the aerobic lagoon improves nutrient removal, and a higher temperature in the anaerobic lagoon increases the biogas production.
Heat energy in the exhaust gases from the cooking process is used to preheat raw materials like biosolids or dissolved air flotation skimmings prior to the fat removal process.
Oil and protein
Brandon Kyzar, division manager, American Proteins, said some poultry companies look at dissolved air flotation skimmings and biosolids as part of wastewater and not as a byproduct.
Dissolved air flotation skimmings are comprised of oil, water and protein, but many poultry plants pay to have the skimmings land applied. When injected underground, the skimmings and other wastewater treatment biosolids (sludge) serve as soil amendments, but their disposal is a net cost to the processor.
American Proteins prefers to call items like dissolved air flotation skimmings “supplemental protein nutrient," according to Chris Jones, American Proteins environmental manager.
The Cuthbert plant has $10 million worth of equipment which allows it to remove water from supplemental protein nutrient and separate out the fat, leaving a high-protein feed ingredient. High fat prices have driven the economics of processing supplemental protein nutrient, and the Cuthbert facility now receives supplemental protein nutrient from several plants, including processing the nutrient generated on site.
Jones said that pet food companies don’t want any processed dissolved air flotation skimmings or supplemental protein nutrient in the ingredients they buy. Cuthbert can process supplemental protein nutrient without impacting their pet food products.
When fat prices were lower and natural gas prices were higher, the Cuthbert plant used reclaimed fat in its boilers. Now that natural gas prices are lower, the fat can be sold for use in animal feeds or for making biodiesel.
The Cuthbert facility processes seven days per week and there are more than 18,000 gallons per minute of recycled water flowing though the plant at any given time. The water is used to control temperatures and collapse vapors on the cookers and feather condensers.
The recycled water is also used in the company's conditioning building, which lowers the temperature of the plant operating air before it enters the biofilters. The majority of the plant wash down water is recycled water, and the water sprayed on the biofilter media to maintain the correct moistures is recycled water. Recycled water is used to wash out all of the trailers on the inside after dumping their load, and then the whole truck and trailer are washed again before they leave the plant.
“If the truck is clean it won’t smell as much,” Jones said. “Since the truck has American Proteins' name on the side we don’t want it to smell or look dirty.”
License to operate
Kyzar said taking care of the environment provides American Proteins its “license to do business, and if you loose that license to do business you might as well just shut the doors.”
Odor control plays a part in maintaining a license to operate for a renderer and Kyzar said it all starts with logistics. “Logistics are a key to keeping odors down. Once material rots, you can spread the smell throughout your plant.” Receiving fresh offal at the facility and processing it quickly with the best technology ensures that odor is not a major problem.
The Cuthbert facility also goes the extra mile to maintain its ability to land apply its treated effluent. Around 400,000 gallons of wastewater a day are treated in the facility, and the condensate from the condensers makes up the majority of this. Five spray fields totalling 240 acres receive the treated effluent and produce a crop of rye grass hay in the winter and Bermuda grass in the summer. A total of 89,000 bales of hay are produced in a year.
The original permit allowed for a certain number of pounds of nitrogen to be land applied per acre and no soil sampling was required. American Proteins did some soil sampling and determined that the grass wasn’t using all of the nitrogen they were allowed to apply, so more acreage was added to the spray fields. Now application of nutrients is made based on plant needs and soil tests.
Since reused water now cools the condensers, there are times of the year when plant operations generate no water for land application. A 20 million-gallon lagoon for water storage allows for water to be carried forward from the winter months (when there is a surplus) into the summer when plant needs exceed the water generated by operations.