Evaluation and application of a dynamic emissions chamber for quantifying gaseous emissions from laying hen manure

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Acevedo Perez, Ricardo Rafael
Iowa State University; Digital Repository @ Iowa State University
ammonia emission; carbon dioxide emissions; emission mitigation; flux chamber; mobile air emissions monitoring unit
thesis / dissertation description
The need to quantify air emissions from animal feeding operations (AFOs) with relative ease and reasonable certainty continues to rise. Exploration of practical means to reduce air emissions also calls for less sophisticated but reasonably dependable methods to quantify the treatment effect. Although mobile air emissions monitoring units (MAEMUs) capable of precise and real-time emission measurement is the norm for continuous, intensive monitoring of emissions from mechanically ventilated animal facilities, their relative immobility and high cost are limiting their widespread use. Several other methods, such as gas-washing, micro-meteorological, wind tunnel, flux chamber, and mass-balance methods, have been employed to accommodate different measurement needs. Flux chambers have the advantages of being portable, small size, low cost, and less labor requirement. However, the performance of flux chambers and thus the measured emission values may be subject to the influence of the system design and operational characteristics. The focus of this study was on the evaluation and application of a dynamic flux chamber (DFC) for quantifying NH3 and CO2 emissions from laying hen manure.The first objective, as reported in Chapter 2, was to assess the impact of operational parameters on the DFC, including: air exchange rate expressed in air changes per hour (ACH), and air turbulence or velocity over the manure surface resulting from different air inlet angles into the DFC space. Results of laboratory tests with laying-hen manure revealed that measured NH3 and CO2 emissions are positively related to DFC air exchange rate. Higher air velocities (0.07 vs. 0 m∙s-1at 39 ACH) over the manure surface as a result of the different air inlet angles (0 vs. 45 degrees) were shown to positively affect the measured gaseous emissions.The second objective, as reported in Chapter 3, was to assess gaseous (NH3 and CO2) emissions of high-rise layer houses as measured with the DFC vs. MAEMU. The preliminary data showed that NH3 emission from the stored manure surface or piles measured with the DFC was 8% to 16% that of the whole barn measured with the MAEMU, while CO2 emission from the manure surface was 1% to 4% of the barn emission. The preliminary results obtained with DFC concerning the dietary efficacy of ammonia emission reduction were mixed as compared to those obtained with the MAEMU.