ARS | Publication request: Cumulative Ammonia Quantification from Litter with Instantaneous Flux Estimates

Submitted to: International Poultry Forum Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: January 3, 2007
Publication Date: January 22, 2007
Citation: Miles, D.M., Rowe, D.E., Owens, P.R., Moore Jr., P.A., Smith, D.R. 2007. Cumulative ammonia quantification from litter with instantaneous flux estimates [abstract]. International Poultry Scientific Forum. p. 54.

Technical Abstract: Challenges, such as method viability and litter heterogeneity, persist in measuring ammonia (NH3) emitted from broiler housing. A chamber acid trap (CAT) system was designed to investigate NH3 generation. The objectives of this work were to assess the variability of litter NH3 using the CAT system and compare the CAT quantification of NH3 to instantaneous (i-) flux estimates. Commercial litter was collected prior to flock 19 (reusing pine shavings bedding). The bulk sample was homogenized and randomly assigned in 50 g increments to each of 48 chambers. The CAT system provided approximately 100 ml/min of air to each 1000 ml chamber which exhausted into a series of two flasks containing boric acid. On selected days, the boric acid was titrated with HCl to assess NH3 volatilization. The i-flux method inverted a 1.98 L container over a 93.8 cm2 tray (chamber footprint) containing a litter sample. At roughly 2 min intervals, a photoacoustic multigas analyzer drew in (and returned) the gas sample from the head space of the inverted container to determine NH3 concentration. The CAT cumulative NH3/chamber collected after 1 d averaged 9.05 ± 0.58 mg N and 52.40 ± 1.36 mg N on d 16. The cumulative NH3 release was predicted as (mg N) = 15.7 ln(day) + 7.16, with R2= 0.99. Converting the cumulative NH3 from the CAT experiment to flux units gave estimates of 40 mg m-2 h-1 on d 1 and 15 mg m-2 h-1 on d 16. The i-flux procedure indicated 54 mg m-2 h-1 at 2 min and 29 mg m-2 h-1after 8.5 min. An NH3 reduction over time is expected; the results indicate that the time selected for flux greatly impacts the magnitude of the estimate. Therefore, extreme care would be required to apply flux calculations in regulatory circumstances. The CAT system offers a viable method for lab-scale NH3 volatilization mechanistic studies. The relationship of cumulative NH3 and i-flux requires further characterization, but promise exists for developing predictive models and correlation between the two methods to provide rapid assessment protocols for litter management as regulations for air quality emerge.