Effects of Dietary Modification on Laying Hens in High-Rise Houses: Part I – Emissions of Ammonia, Hydrogen Sulfide and Carbon Dioxide
Dietary manipulation can substantially lower ammonia (NH3) emissions from laying-hen houses or manure storage. Recent lab studies showed a reduction of 40–60% in ammonia emissions for an experimental (EcoCalTM) diet as compared the standard or control diet. However, adoption of a mitigation technology at commercial production level should be preceded by substantial field verification tests to document not only NH3 emission reduction, but also impact of the strategy on production performance of the hens and cash returns. A study to assess the effects of feeding diets containing EcoCal on NH3, hydrogen sulfide (H2S), and carbon dioxide (CO2) emissions, laying-hen production performance, and economic returns was conducted at a commercial laying-hen farm in central Iowa. Two houses (256,000 or 262,000 hens per house) were used for the study. Hens in one house were fed the EcoCal diet while hens in the other house were fed a standard or control diet containing no EcoCal. A state-of-the-art mobile air emissions monitoring unit (MAEMU) and the associated sampling system were used to continuously monitor the gaseous concentrations, ventilation rate and environmental conditions. Comparative data collected from December 2006 to May 2007 are presented in this paper. Data from this period showed that the EcoCal diet led to NH3 emission reduction by up to 23.2% (0.86±0.04 and 1.12±0.03 g/d·hen for EcoCal and Control diet, respectively), at the same time, H2S emission increased by up to 134% (4.38±0.20 and 1.82±0.07 mg/d·hen for EcoCal and Control diet, respectively), although the magnitude of H2S emission is rather small for both dietary regimens. Data on the hen production performance are reported in a companion paper (Roberts et al., 2008).
Evaluation of a Flux Chamber for Assessing Gaseous Emissions and Treatment Effects of Poultry Manure
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 the 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. The objectives of this study were: (1) to develop a portable emission flux chamber system (EFC) for in-situ measurement of ammonia (NH3) and carbon dioxide (CO2) emissions from manure; (2) to assess gaseous (NH3 and CO2) emissions of high-rise layer houses with the EFC vs. MAEMU; and (3) to evaluate the adequacy of using the EFC to determine the effects of dietary regimens on ammonia emissions from the layer manure. The preliminary data showed that NH3 emission from the manure surface measured with the EFC 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 EFC concerning the dietary efficacy of ammonia emission reduction were mixed as compared to those obtained with the MAEMU. More evaluation is continuing.
Far-field dispersal modeling for fuel-air-explosive devices
A computer model for simulating the explosive dispersal of a fuel agent in the far-field regime is described and is applied to a wide variety of initial conditions to judge their effect upon the resulting fuel/air cloud. This work was directed toward modeling the dispersal process associated with Fuel-Air-Explosives devices. The far-field dispersal regime is taken to be that time after the initial burster charge detonation in which the shock forces no longer dominate the flow field and initial canister and fuel mass breakup has occurred. The model was applied to a low vapor pressure fuel, a high vapor pressure fuel and a solid fuel. A strong dependence of the final cloud characteristics upon the initial droplet size distribution was demonstrated. The predicted fuel-air clouds were highly non-uniform in concentration. 18 refs., 86 figs., 4 tabs.