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National Air Emissions Monitoring Study

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The National Air Emissions Monitoring Study (NAEMS)

  • NAEMS monitored 24 sites at animal feeding operations (AFO) in 9 states over two years to measure emissions of particulate matter, ammonia, hydrogen sulfide, and volatile organic compounds.
  • The study was funded by the AFO industry as part of a 2005 voluntary air compliance agreement with EPA. Purdue University led the research team with EPA oversight.
  • The types of AFOs monitored included those raising pigs and broiler chickens, egg-laying operations, and dairies. Participating AFOs made their operations available for monitoring for two years and worked closely with the researchers, industry experts, and EPA during the study.
  • A separate industry study monitored emissions from a broiler chicken site in Kentucky for one year. The industry also worked closely with EPA during that study and followed EPA monitoring and quality assurance guidelines.
  • In addition to monitoring key pollutants, Purdue University researchers gathered data on how animals were managed at the feeding operations, including numbers of animals, how they were housed, and how their waste was managed. They also gathered data on weather.
  • EPA used information gathered in NAEMS, along with other information provided as part of a Call for Information, to develop draft emission estimating methodologies for the AFO sectors that were monitored. Such methodologies are commonly used to estimate emissions from industries where site-specific monitoring data are not available. A 2002 report by the National Academy of Sciences called on EPA to develop scientifically credible methodologies for estimating emissions from AFOs.

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NAEMS Status

EPA is currently analyzing the data gathered during NAEMS and a 2011 Call for Information related to the development of emission estimating methodologies for AFOs. EPA issued an updated Call for Information requesting additional relevant VOC data in September 2019. 

Timeline for the Release of Emission Estimating Methodologies for AFO Emissions
Date Milestone
July 2020 Draft models for ammonia, hydrogen sulfide and particulate matter emissions from swine farms
November 2020 Draft models for ammonia, hydrogen sulfide and particulate matter emissions from poultry (broiler and layer) farms
March 2021 Draft models for ammonia, hydrogen sulfide and particulate matter emissions from dairy farms
July 2021 Draft models for volatile organic compound emissions from swine, poultry and dairy farms
TBD Stakeholder review period
TBD Finalization of all emission estimating methodologies

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The final reports for data gathered at each site monitored during NAEMS are available in EPA's archive. (search term: "2012 monitored AFOs") Search EPA Archive

image of the United States showing monitoring site locations

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Peer Review of the Analyses from NAEMS

The EPA Science Advisory Board (SAB) conducted a peer review of the statistical analyses and draft emissions methodologies for animal feeding operations. Materials related to this peer review, including charge questions, meeting minutes, and the SAB report are available from the Animal Feeding Operations Air Emission Estimation Methodologies SAB panel.

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2005 Voluntary AFO Air Compliance Agreement

  • EPA announced the voluntary Air Compliance Agreement in 2005, with goals of reducing air pollution, monitoring AFO emissions, promoting a national consensus on emissions estimating methodologies, and ensuring compliance with requirements of the Clean Air Act and notification provisions of the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), and the Emergency Planning and Community Right-to-Know Act (EPCRA).
  • EPA worked with industry representatives, state and local governments, environmental groups and other stakeholders to develop the voluntary agreement. Approximately 2,600 AFOs, representing nearly 14,000 facilities, received EPA approval to participate.
  • Participating AFOs paid a civil penalty of between $200 and $100,000, based on the size and number of facilities in their operation. They also contributed to a fund to cover the cost of the monitoring study.
  • As part of the agreement, EPA agreed not to sue participating AFOs for certain past violations of the Clean Air Act, CERCLA and EPCRA, provided that the AFOs comply with the agreement’s conditions. However, the agreement does not limit EPA’s ability to take action in the event of imminent and substantial danger to public health or the environment. It also preserves state and local authorities’ ability to enforce local odor or nuisance laws.
  • Once EPA publishes final emissions estimating methodologies for an AFO’s animal sector, that AFO must apply the final methodologies to determine what actions, if any, it must take to comply with all applicable Clean Air Act, CERCLA and EPCRA requirements.

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