Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 27, 1999
Publication Date: N/A
Interpretive Summary: Concentrated animal systems increase production efficiency but also increase problems associated with animal waste disposal and potential environmental pollution. Of the 56 million swine in the U.S., about 75% use liquid lagoon or slurry systems for waste holding or disposal. Atmospheric emissions of ammonia (NH3) from these systems have been related dto water eutrophication and species change in natural ecosystems. Non- disturbing micrometeorological measurement techniques were used to evaluate trace gas emissions from a swine facility containing 12,000 animals with a 4-stage lagoon system. Ammonia emissions averaged 12 kg NH3 /ha/day over the three year study. Ammonia emissions varied diurnally and seasonally and were highly correlated with windspeed and water temperature. Previously, it has been assumed that 89 to 90% of the N lost from lagoons was through NH3 volatilization. In this study, we found greater emissions of N2 (37 kg/ha/day) than NH3 which indicates that lagoon systems may have less environmental impact due to smaller NH3 emissions than previously thought. This study also indicates the potential for the development of management techniques which would decrease NH3 losses by enhancing N2 emissions.
Technical Abstract: Seventy-five percent of swine production systems in North America use anaerobic or liquid/slurry systems for waste holding or disposal. For system design and evaluation of the effect of animal concentrations on the regional soil, surface and ground waters, and atmospheric environments, accurate emissions data and emission factors are needed for engineering, planning, and regulatory agencies. Non-invasive techniques were used to evaluate trace gases without disturbing the meteorology or lagoon system being measured. Micrometeorological and gas sensors were mounted on a submersible barge in the center of the lagoon for use with flux-gradient methodology to determine trace gas fluxes over extended periods. Collateral measurements included lagoon nutrient, dissolved gas concentrations, and sludge gas mass flux. Ammonia emissions varied diurnally and seasonally and were highly correlated with wind speed and water temperature. Nutrient loading measurements showed that mobile ions, which were non-volatile, were constant throughout four successive lagoons. Immobile ions concentrated primarily in the sludge layer of the first lagoon. Nitrogen loss or reduction between lagoons one through four was 18, 48, and 34%, respectively, suggesting possible denitrification in the secondary lagoons. Nitrogen mass balance showed losses by gas emissions (15%), retention (1%), seepage (5%), and irrigation onto crops (2%). Measurements of denitrification N2 losses suggest as much N2-N lost as from NH3-N. Ammonia gas emissions are not as large a percentage of total nitrogen input to the lagoons as previously thought but unaccounted-for nitrogen requires further research.