Challenges of CAFO Waste Management

JOUR to 5,000 and 2,000 mg/L, respectively!. Because of the large quantity and high contents of organic matter and nutrients, manure and wastewater from CAFOs have caused growing environmental concerns. The animal wastes have the potential to contribute pollutants such as nutrients, organic matter, pathogens, heavy metals, hormones, antibiotics, and ammonia to the environment. These pollutants can cause potential contamination to surface and groundwaters and negative impact to air quality if they are not properly managed. Currently, anaerobic-lagoon/sprayfield irrigation is the most widely used system for animal-waste management in the United States. In such a system, animal manure and wastewater are treated and temporarily stored in an anaerobic lagoon where organic matter is degraded, and the effluent and sludge of the lagoon are irrigated onto a cropland for nutrient utilization. Environmental concerns about the current waste management system include odor and ammonia emissions from the open lagoon and sprayfield, methane emission from the open lagoon, and accidental lagoon spills due to severe weather conditions. Finding solutions for these concerns can be quite challenging, understanding that effective solutions need to balance cost with environmental performance and operational ability of the farm enterprises. There have been considerable regulatory efforts to ameliorate the impacts of animal waste on air and water quality in the last two decades. A common characteristic of these efforts is the adaptation of the technologies widely used in the treatment of municipal and industrial wastewaters. However, the cost of many of these technologies ~e.g., aeration, typical nitrification/ denitrification process! is prohibitively too high for their application on animal-waste treatment. To minimize water quality and public health impacts from AFOs, the U.S. Department of Agriculture ~USDA! and U.S. Environmental Protection Agency ~EPA! developed a unified national strategy for feed and manure management in AFOs in 1999 ~http://www.epa.gov/npdes/pubs/finafost.htm!. According to the strategy, all AFO owners and operators are expected to develop and implement technically sound and economically feasible sitespecific comprehensive nutrient management plans ~CNMPs! including feed management, manure handling and storage, and land application of manure. In December 2002, the EPA published ‘‘Concentrated Animal Feeding Operations ~CAFO! Final Rule’’ ~http: //cfpub1.epa.gov/npdes/afo/cafofinalrule.cfm?program_id 57! to regulate CAFO waste management. All CAFOs have a mandatory duty to apply for a National Pollutant Discharge Elimination System ~NPDES! permit. NPDES permits under the authority of the Clean Water Act require CAFOs to develop CNMPs and to meet other conditions that minimize the threat to water quality and public health and otherwise ensure compliance with the requirements of the Clean Water Act. Only CAFOs that have successfully demonstrated no potential to discharge may avoid a permit. Considerable efforts have been made in the development of cost-effective, environmentally-friendly alternative technologies for CAFO waste management. A variety of anaerobic digesters Jiayang Cheng Associate Editor, Assistant Professor, Dept. of Biological and Agricultural Engineering, North Carolina State Univ., Raleigh, NC 27695-7625. E-mail: jay_cheng@ncsu.edu