Synergistic ammonia losses from animal wastewater

Thin-layer models are commonly used to estimate NH3 emissions from liquid waste. However, such models differ in their ability to accurately reproduce observed emissions, which may be partly due to an incomplete mechanistic understanding of NH3 volatilization. In this study, NH3 release from pure solutions of (NH4)2SO4 (AS), swine pit liquid (PL), swine lagoon liquid (LL), dairy lagoon liquid (DLL), and dairy manure liquid (DML) were evaluated under controlled conditions (pH 7.6 and temperature 20 °C). Relationships between the NH3 release and pH, temperature, and total ammoniacal nitrogen (TAN) were established. Under similar TAN conditions, the NH3 release was higher for PL, LL, DLL, and DML than for AS. Pure solutions of AS that were spiked with NaHCO3 showed NH3 emissions rates that were comparable to DML, DLL, LL and PL. The enhanced NH3 emissions of PL, LL, DLL and DML were therefore explained by linkages between TAN and HCO3−.

► Measured ammonia emissions from pure (NH4)2SO4 solution and animal wastewater.
► Observed enhanced ammonia emissions from both swine and dairy wastewater.
► Multiple reactions in animal wastewater control NH3 emissions across thin layers.
► Modeling application needs to go with better understanding of ammonia emissions.