Air emissions and animal agriculture

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“Air Emissions and Animal Agriculture” a new online resource developed by Michigan State University Extension and Purdue Extension provides science-based information on food animal production in the United States and the odors and air emissions associated with livestock and poultry production.

To the general public the acronym “CAFO” is, for the most part, only a term used to reference any large livestock farm. Few realize the term “Concentrated Animal Feeding Operation” (CAFO) originated as a United States Environmental Protection Agency (US EPA) term for categorizing livestock farms by size, manure handling system and days on pasture.

To those rural residents not actively engaged in livestock/poultry production the odor associated with those farms may be the emission of greatest concern. A person’s perception of an odor depends on five characteristics: the odor’s intensity, degree of offensiveness, character, frequency and duration. Frequency and duration of odor events are most often the factors that trigger odor nuisance complaints.

Odors on livestock farms originate from 3 distinct areas of production: the animal housing, manure storage and land application. While ammonia and hydrogen sulfide from livestock farms are emissions of concern, most odors from animal production are related to the release of volatile organic compounds (VOCs). VOCs are released during the decomposition of manure. These small compounds attach themselves to dust particles as they leave the production site. Therefore many of the recommended odor control practices for livestock farms include capturing and/or treating dust particles. Oil sprinkling, bio-filters, physical barriers and vegetative buffers are all practices livestock and poultry farmers use to capture dust and reduce the odors coming from their farms.  

The three greenhouse gases of greatest concern from farms are carbon dioxide (CO2), methane (CH4) and nitrous oxide (N20). Methane has 24 times and nitrous oxide 298 times the global warming potential, or “greenhouse effect,” of CO2. When comparing greenhouse gas emissions, CH4 and N2O are expressed as their equivalency to CO2 or CO2e.

Carbon dioxide is released during the breakdown of manure and from the animal’s natural respiration process. Methane is released during the animal’s normal food digestion process and from the manure storage area. Nitrous oxide is released from the manure storage area. Some current tools used to calculate the carbon footprint of animal and poultry products include the N2O release associated with the production of feed grains. Because N2O has 298 times the global warming potential of CO2, including the N2O associated with feed production has a profound impact on the carbon footprint of meat, dairy and egg products. Like all tools for making comparisons, one needs to be mindful of the inputs going into the carbon footprint calculations used to make comparisons. While the study of the carbon footprint of different agriculture products is still in its infancy Air Emissions and Animal Agriculture does compare those products whose carbon footprint has been well documented.

 As researchers learn more about the greenhouse gases from livestock/poultry farms recommended practices to reduce these emissions may include improved diets, increased feed efficiency, improved energy efficiency, manure storage covers and unique manure handling and storage technologies. To learn more about the greenhouse gasses associated with livestock production see:

To learn more about these topics visit Air Emissions and Animal Agriculture, a new online resource developed by Michigan State University Extension and Purdue Extension, that pulls together information on the odors, greenhouse gases and other air emissions associated with livestock and poultry production, and information such as what is a CAFO. The development of Air Emissions and Animal Agriculture was funded by the MSU Animal Agriculture Initiative. This informative internet resource can be found at:

Source: Gerald May, Michigan State University Extension

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Texas  |  December, 11, 2011 at 10:13 AM

As someone growing up on the south side of Amarillo Tx I often dealt with the smell of the stock/feed yards south of town ... when the wind blew just right the odor could be very strong ... the better the beef industry wasdoing the stronger the smell ... most people in Amarillo didn't comment on the smell by saying "that sh*t stinks" ...the most common comment that was made was "smell that money! " it was a clear indication that the economy was doing well .....and was generally said with a smile on the com-mentors face

Ham  |  December, 13, 2011 at 10:53 PM

You're missing a crucial point re global warming potential. There are serious implications of focusing in the 100 year statistics (25 times) instead of the 20 year statistics (72 times CO2). This is explained at . Hamilton

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