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Reduce ammonia emissions in barns.

March 31, 2011
Simple changes can greatly reduce odor and pollution while improving the cow environment and preserving the nutrient value of manure.
 
Sources of ammonia.
Livestock production and fertilizer application are identified as major sources of atmospheric ammonia emissions. Ammonia emissions into the atmosphere occur primarily from livestock buildings, open feedlots, manure storage facilities, during manure handling and treatment, and when manure is applied on land.
 
Reasons to reduce ammonia emissions:
 
·         Improved health of workers and animals: Ammonia poses a threat both to animals and agricultural workers in livestock facilities. It is a significant respiratory hazard for workers who experience continuous, long-term exposure to the gas at concentrations greater than 25 parts per million (ppm). In addition to respiratory effects, ammonia can cause skin and eye irritation and displace oxygen in the bloodstream. Long-term exposure to ammonia can cause pneumonia, both in the livestock and workers.
·         Better fertilizer: Volatilization of ammonia significantly reduces the nitrogen fertilizer content of manure. The financial impact can be very large, also see “Manure Injection” article.
·         Reduced pollution: Airborne ammonia contributes to acid rain and so leads to soil acidification, while also delivering nutrients to waterways, which contributes to algal blooms.
·         Greenhouse gas reduction: Ammonia is a potent greenhouse gas and agricultural manure is a significant contributor.
·         Odor reduction: The same practices that reduce ammonia emissions also reduce odor emissions.
 
Proper barn design and practices greatly reduces the amount of ammonia emitted in the barn:
 
·         Handle manure as a liquid: Liquid manure is lower pH, which volatilizes less ammonia. A layer of water in the bottom of reception pits reduces emissions.
·         Small volume reception pits: Decreasing the length of time manure remains in a livestock building is an important factor in reducing ammonia emissions, which can be achieved by the frequent removal of manure from livestock buildings. Small reception pits also require less agitation before manure removal, resulting in less emissions.
·         Small surface area in reception pits: Ammonia emissions from a liquid manure surface are proportional to the surface area of the manure. Therefore, decreasing manure surface area by changing the shape and dimensions of a manure storage facility will reduce ammonia emissions from the barn.
·         Smooth, sloped floors: The type of floor area exposed to manure in animal housing facilities can have a significant effect on the emissions rate of ammonia. Emissions of ammonia from the solid part of the floor can be reduced by using a smoothly finished inclined or convex surface.
·         Clean floors: Keeping buildings and animals clean and dry is essential for reducing ammonia emissions. Manure in alleyways presents a very large surface area and promotes ammonia emission. Operate alley scrapers continuously.
·         Low speed ventilation: Using ventilation techniques that create low air velocities around surfaces exposed to manure will also reduce ammonia emissions. Air speeds across manure-covered surfaces should be minimized since the amount of ammonia gas given off by manure is increased with air speed.
·         Manure separation: Separating manure from urine may slow the rate of reaction that leads to ammonia generation and may help minimize ammonia volatilization. See information on in-floor manure tube system in the Manure Systems section.
·         Balance rations: Nitrogen fed in excess of the requirements of livestock animals is not retained by the animal’s body but is simply passed out in the urine and feces. Matching feed to the nutritional requirements of animals reduces nitrogen excretion without affecting productivity. While production can be significantly affected if protein levels are reduced excessively, research found that ammonia emissions could be reduced in dairy cows by up to 20 to 30 per cent by manipulating dietary crude protein types and levels.
 
The short story in the barn: Alleys should constantly cleaned into small holding pits and the manure should be moved out of the barn as quickly as possible.
 
 
Practices to reduce ammonia emissions from storage and field:
 
·         Covered storage: Covers prevent ammonia from escaping to the atmosphere, and gases that are trapped under the cover are aerobically decomposed by microorganisms. Covers may include roofed storages or floating covers.
·         Crusted manure: Significant crusts may form on long term manure storages which reduce the escape of ammonia to the atmosphere. It takes time to establish a thick crust on freshly agitated or emptied storages, resulting in a significant loss of ammonia during this period. Biocovers such as chopped straw can be added to much more quickly establish protection against ammonia loss. Crusts or biocovers should be at least 8 – 12 inches thick. Crusted storages should be filled from the bottom to preserve the top crust.
·         Minimize agitation: The storage design and bedding practices affect the amount of agitation required. Spraying manure above the surface increases volatilization.
·         Inject manure: Ammonia losses are very high when manure is broadcast on the surface. Deep injection reduces losses approximately 80%.
 
The short story for manure storage and application: Manure should always be covered, both in storage and during application (injection).
 
Sources: Alberta Agri-Facts, Agdex 729-4
U.S. EPA: www.epa.gov/nitrousoxide/sources.html
Field application of liquid manure: Perennial forages (Bittman et. al., Agriculture Canada)

 

 

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