Gaseous nitrogen emissions from anaerobic swine lagoons: Ammonia, nitrous oxide, and dinitrogen gas

Seventy-five percent of swine (Sus scrofa) production systems in North America use anaerobic or liquid-slurry systems for waste holding or disposal. Accurate emissions data and emission factors are needed for engineering, planning, and regulatory agencies. These data are used For system design and evaluation of the effect of animal concentrations on the regional soil, surface and ground waters, and atmospheric environments. Noninvasive 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 renter of the lagoon for use with flux-gradient methodology to determine trace gas fluxes, without disturbing atmospheric transport processes, 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 windspeed and water temperature. Nutrient loading measurements showed that mobile ions, which were nonvolatile, were constant throughout four successive lagoons. Immobile ions concentrated primarily in the sludge layer of the first lagoon. Measurements of denitrification N-2 losses suggest as much N-2-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.