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Production of Food Processing Biosolids And Their Use As Animal Feed: An Overview

Charles R. Stack, M.P.H., Charles Stack & Associates Inc. Prasad S. Kodukula, Ph.D., Woodward-Clyde Consultants

Presented to the Environmental Issues Committee

Association of American Feed Control Officials, Inc. April 24, 1995

Background Modern food processing facilities in the U.S. employ numerous processing stages that produce wastewater. Regardless of the type or size of the facility, raw products are received; sorted according to quality; and processed into dry, canned, frozen, and other forms as final product. Wastewater streams are generated from raw product washing, product manufacture and processing, spills and routine sanitation and maintenance procedures. Wastewater streams generated during food processing operations become contaminated with organic matter from contact with raw and manufactured products. The composition of contaminants varies depending upon the raw materials consumed by the facility, manufacturing processes, and final product mix. However, these wastewater streams contain, among other things, fats, oils and greases (FOG); sugars; starches; proteins; and other organic compounds at higher concentrations than found in domestic sewage. These substances demand oxygen during biodegradation (measured as five day biochemical oxygen demand, BOD5) and exert strong loadings to surface waters, land applications sites, and publicly owned treatment works (POTW) depending upon the method of treatment. Food processing wastewaters also have elevated levels of nutrients such as nitrogen and phosphorus, which could degrade the environment if released without some form of treatment. To mitigate environmental effects of food processing wastewaters, the U.S. Environmental Protection Agency (EPA) has promulgated pretreatment standards requiring that wastewaters are treated prior to POTW discharge. Similarly, treatment is required for direct discharge to receiving waters or for land application. Food processors employ a wide variety of wastewater treatment processes and technologies to pretreat their wastewaters. These include screening, gravity sedimentation, flotation, flow equalization, and biological treatment processes. In-plant waste reduction strategies are increasingly used to reduce waste generation and conserve water, ultimately reducing operating and wastewater treatment costs. However, despite aggressive in-plant waste reduction, some level of organic contamination in wastewater discharges inevitably occurs. Environmental regulations and sewer ordinances are becoming increasingly stringent on food processing discharges and require pretreatment for removal of FOG, nutrients, and BOD5 prior to sewer or land disposal. The ultimate cost of pretreatment will be influenced by sewer disposal surcharges, level of

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pretreatment required for compliance, penalties for noncompliance, and complexity of the selected treatment processes. Biological wastewater treatment processes have been employed by food processors for many years. These processes utilize the natural biodegradation by aerobic or anaerobic microorganisms to convert FOG and BOD5 into biological cell mass (biosolids) and waste gases such as carbon dioxide or methane. These gases are easily handled and discharged into the environment with minimal impact, and the biosolids are disposed through landfilling, land application, incineration or composting. Regulations have been promulgated recently by the EPA restricting the landfilling and land application of biosolids due to potential for contamination of groundwater and surface waters by runoff, contamination of crops with toxics or heavy metals, vector attraction, spread of pathogens, and similar public health concerns (40 CFR Parts 257 and 503, U.S. E.P.A.). In order to remain compliant, some of the options being considered by food processors using biological treatment systems are: modify operations to reduce biosolids production, increase waste biosolids storage capacity, eliminate runoff and groundwater contamination at land application sites, monitor land application rates to control nutrient and metals loadings, and apply biosolids onto crops such as alfalfa or reed canary grass for nutrient uptake. Dewatered biosolids must pass rigorous tests for free moisture, hydrocarbons, and leachable metals and toxics before disposal in landfills. These regulatory restrictions have reduced available options for disposal of biosolids and increased costs to food processors. Labor costs are also increased for operating and maintaining biosolids handling and management equipment, laboratory testing, and sampling, among other things. In order to decrease the costs associated with food processing biosolids disposal, new technologies and strategies have been developed. Anaerobic biological wastewater treatment is used by some operations since this treatment produces less biosolids per unit mass of BOD5 removed than aerobic processes. Other options include composting to produce a stabilized soil amendment, incineration and production of construction materials such as brick or aggregate. However, many of these technological advances require substantial capital investment and operational expertise, and the processor must find outlets for recovered products. On potentially cost-effective option appears to be the use of food processing biosolids as an animal feed. Previous research has proven that wastewater biosolids from food processing treatment systems have nutritional value when used as a component in animal feed. Biosolids primarily consist of bacterial and protozoan cell material, residual food products such as FOG or proteins, and traces of minerals and other matter. However, the regulatory status of usage of biosolids for animal feed remains unresolved, and questions persist regarding the safety and efficacy of biosolids used in this manner. Nevertheless, conversion of biosolids into animal feed may be a viable option for byproduct recovery at

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food processing facilities in order to reduce disposal costs and increase compliance with environmental regulations. Biological Treatment Processes Producing Biosolids One of the most common biological wastewater treatment processes used by food processor in the U.S. is aerobic treatment. Wastewater effluents are treated in lagoons or tanks under aerobic conditions, stimulating the metabolism and growth of aerobic bacteria and protozoans. These microorganisms convert residual FOG, BOD5, and nutrients into cell mass (biosolids) and carbon dioxide. Aerobic conditions are maintained by natural exposure to atmosphere; photosynthesis; or mechanical aeration with blowers, diffusers, surface aerators, or other means. Aerobic systems produce approximately 0.5 pounds of biosolids per pound of BOD5 destroyed. Anaerobic systems produce 0.1 pounds of biosolids per pound of BOD5 destroyed; however, these systems are not in common use in the U.S. food processing industry. Food processing plants in the U.S. must only use certain chemicals approved for human contact and consumption during processing, so food processing effluents tend to have low levels of toxic contaminants. Including heavy metals, pesticides, or petroleum hydrocarbons. However, contamination of plant effluents by toxic substances may occur from equipment malfunction, spills, operator error, maintenance procedures, or contaminated raw materials. The biosolids produced during biological treatment will tend to accumulate many of these toxic substances onto the interior or exterior of the cells, causing contamination and complicating disposal. Biosolids will also accumulate nutrients such as phosphorus and nitrogen, and FOG tends to agglomerate onto the surfaces of biosolids. Biosolids may also become contaminated during routine operation if inorganic coagulants such as ferric chloride or organic polymers are used to enhance solids capture and settling in clarifiers or dewatering operations. Food processing operations generate a variety of flows including non-contact cooling tower or boiler blowdowns and sanitary streams from plant toilets, showers, and sinks. If these flows are mixed with process wastewaters for combined biological treatment, the biosolids will become contaminated with human fecal matter and treatment chemicals such as sanitizers, biocides, or disinfectants. These may increase the pathogen burden of the biosolids and alter their chemical makeup to increase toxicity. Utilization of Food Processing Biosolids as Animal Feed Biosolids from food processing effluents contain significant amounts of proteins, FOG, amino acids and other desirable nutrients. Feeding trials with ruminants have shown that these biosolids, if uncontaminated with heavy metals or toxic substances, contribute to weight gains of animals in controlled feeding trials. Based upon these properties, some food processing operations have incorporated biosolids into animal feed programs as a disposal option.

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Despite the potential benefits and cost reductions achieved by using food processing biosolids as animal feed, the practice is presently not approved by the FDA or the American Association of Feed Control Officials (AAFCO). Valid public health concerns include potential for contamination with toxic substances, human or animal pathogens and lack of dietary and nutritional standards. These issues are further complicated by the variety of biological processes employed by food processors, differences in effluent characteristics of different operations, and use of chemicals such as coagulants or polymers to enhance the treatment process. In order for food processing biosolids to become acceptable for use in animal feed, a number of issues need to be addressed. These include:

• Source of Wastewater and Presence of Toxics and/or Pathogens A variety of wastewater sources may be identified in modern food processing operations. Each source may contribute undesirable contaminants which would reduce the value of biosolids as feed. Operations processing raw vegetables such as potatoes, sugar beets, and other field crops employ washing and flume operations which can result in significant concentrations of field dirt, herbicides, insecticides, and fertilizers from crop production. Poultry and red meat processing facilities are known to generate wastewater with elevated levels of potentially pathogenic bacteria such as Salmonella. Facilities producing animal feed supplements may release nutritional metals such as zinc, copper, or chromium in sufficient concentrations to impact biosolids composition. Cleaning compounds, acids and bases, and disinfectants also contaminate these streams. Also, sanitary streams reduce the value of biosolids for use as animal feed due to the potential for contamination with human wastes and body fluids. Non-contact streams from cooling towers may contain powerful biocidal agents used to prevent equipment fouling. Blowdowns from boilers and other equipment in the plant also may contain residues from metal scale, conditioning/softening chemicals, petroleum hydrocarbons, paint, refrigerants, and the like.

• Processing and Storage of Final Feed Components Like most animal feed ingredients, biosolids are putrescible and must be handled in a manner to prevent spoilage and microbial growth if they are to be used for feeding purposes. Since biosolids consist primarily of living, single cell microorganisms, some type of processing may be required to reduce or eliminate their biological activity and prevent spoilage. Ideally, such processing would deactivate the biological activity without reducing the quality or nutritional characteristics of the final product. Options for processing similar to those used for food processing and include dewatering, refrigeration, pH adjustment, drying, extrusion, and cooking. Combinations of processing steps may prove to be superior and produce a desirable feed product. Once processed, the biosolids must be stored with the same care given to animal feeds to avoid excessive moisture, vector propagation, odor generation dust and contamination with feces from rodents or other pests.

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• Quality Control and Laboratory Testing Since biosolids are presently not approved for use as animal feed, regulatory action will be required before food processors are legally allowed to process biosolids for this purpose. The FDA, AAFCO, and other agencies must develop appropriate criteria for labeling, testing, processing, and composition of feed products derived from biosolids. Once regulatory approval is obtained, the generator of the biosolids will need to institute a quality control plan to ensure that public health is protected. Issues to be addressed in this plan will include procedures to segregate process from sanitary or non-contact wastewater flows, chemical use studies to eliminate potentially harmful chemicals during food processing and wastewater treatment operations, modification of wastewater treatment plant design and operation to eliminate unapproved chemicals and materials of construction, and routine sampling and analysis of raw and finished biosolid feed products to ensure that nutritional characteristics and contaminant levels are acceptable.

• Appropriate End Uses of Finished Products The primary reason for converting food processing wastewater biosolids into animal feed is economic. Installation of equipment to convert biosolids into animal feed may significantly reduce biosolids disposal costs to processors and save substantial areas of land from land application. Also, some credit for the nutritional content of the biosolids should be given, although customers may initially resist ascribing much value to biosolids feed. Other recovered food processing wastes such as feathers, dissolved air flotation sludges, poultry mortalities and heads, and dehydrated manure solids have nutritional value but are underutilized or rejected by rendering plants and feed mills. Modern vertically-integrated poultry operations, meat packing plants with feedlots, and aquaculture facilities often have feed mills or rendering plants integrated into their structure. By utilizing their own biosolids into their internal feeding operations, they may reduce feed and waste disposal costs and improve regulatory compliance with environmental agencies. These operations could conceivably mix recovered biosolids with other byproducts including flotation sludges, screenings, feathers, waste product, or grains to produce a nutritionally well-balanced product. Modern processing equipment such as extruders, pressure cookers, and centrifuges allow a variety of finished product types with differing characteristics to be manufactured and meet market demand in poultry, aquaculture, and feedlot markets. Processed biosolids could be marketed for fertilizer if appropriate environmental regulations are followed, providing another outlet if the existing markets for biosolids feed products cannot accommodate full production. Recommendations for Future Research The utilization of food processing wastewater biosolids for animal feed may be desirable since an industrial waste product is recovered for use in a productive manner. However, questions remain about the efficacy, safety, and economics of this conversion, and significant changes in existing regulations need to be made. It is recommended that further research and development will need to be pursued in the following general areas:

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• Composition of biosolids according to industry • Nutritional value of end-uses of biosolids feed • Effect of wastewater operations on biosolids quality • Sampling and laboratory analytical techniques to ensure product quality and

safety • Marketing and economics of bioslids feed production and utilization.

REFERENCES: Tchobanglous, George, et.al. Wastewater Engineering: Treatment, Disposal and Reuse, McGraw Hill Inc., 1991. Sell, Nancy J. Industrial Pollution Control, Van Norstrand Reinhold Company, 1981. Hillick, Tracy. “Industrial Pretreatment in the Food Processing Industry: A Municipal Perspective,” Proceedings of the 1990 Food Industry Environmental Conference, Georgia Tech Research Institute, November 1990. Stack, Charles, and Clay Watson. “Control of Odors Generated from Anaerobic Lagoon With Unique Compost/Polystyrene Foam Cover System,” Proceedings of the 1991 Food Industry Environmental Conference, Georgia Tech Research Institute, November 1991. Caton, J.S. et. al. “Evaluation of Dairy Food Processing Wash Water Solids as a Protein Source,” Journal of Animal Science, 69:3406-3434, 1991. Personal Communications between Charles Stack and George Graber, Ph.D., Division of Animal Feeds, Center for Veterinary Medicine, USFDA, February 15, 1992. Personal Communication between Charles Stack and Dr. Daniel McChesney, Division of Animal Feeds, Center for Veterinary Medicine, USFDA, December 27, 1994.