Variability of Atmospheric Ammonia In High-Rise, Caged Layer Composting

Compost Science & Utilization, (2005), Vol. 13, No. 3, 162-167

Richard T. Koenig (1), F. Dean Miner, Jr .(2), Bruce E. Miller (3) and John D. Harrison (3)

1. Crop and Soil Sciences Department, Washington State University, Pullman, Washington
2. Cooperative Extension, Utah State University, Logan, Utah
3. Agriculture Systems Technology and Education Department, Utah State University, Logan, Utah

High concentrations of atmospheric ammonia (NH3) can impact poultry and human health. During composting inside high-rise, caged layer facilities, high concentrations of NH3 are produced due to low carbon to nitrogen ratios of composting materials and the confined building environment. This study characterized the spatial and temporal variability of NH3 during in-house composting as a preliminary step to identifying control measures. Boric acid solutions and gas sensors were used to measure NH3 in 2 m 3 7.5 m grid patterns for three high-rise laying hen structures during composting. Spatial variability was evident in all buildings, with areas of higher NH3 concentration near the center of buildings away from ventilation fans. Ammonia concentrations in the composting area frequently exceeded human health standards for 8-hour and 10-minute exposure periods of 25 and 35 µL L-1, respectively. Ammonia concentrations were lower in cage areas of high-rise structures due to the negative pressure ventilation system venting gas directly from the composting area to the outside of buildings. Over a 6-week composting cycle, NH3 generally increased as compost accumulated in the structure. Over 1-day periods of time, NH3 concentrations varied with fluctuations in outdoor air temperatures and fan operation. During turning of compost, atmospheric NH3 reached a high of nearly 50 µL L-1 for over 30 minutes. Monitoring NH3 and altering the ventilation of poultry houses could reduce NH3 concentrations below critical levels at peak times such as during turning. However, ventilation as a solution to high NH3 levels may not be environmentally sustainable. Other alternatives such as chemical and process controls, structural changes, or biofiltration should be explored to prevent NH3 volatilization or remove NH3 from air vented during in-house composting.

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