Title: Methane and ammonia emissions from New Mexico dairy lagoons in summer Authors
Submitted to: Western Dairy Air Quality Symposium
Publication Type: Proceedings
Publication Acceptance Date: April 20, 2011
Publication Date: N/A
Interpretive Summary: Methane and ammonia are two gases emitted from the lagoons that hold wastewater at commercial dairies. Methane is a powerful greenhouse gas and ammonia has several negative effects on the environment. We studied the loss of these gases to the air at a commercial dairy in New Mexico over two summers in 2009 and 2010. Cows at this typical dairy were kept in large, open corrals and deposited manure was periodically flushed with water and then flowed into the lagoons. Ammonia loss was low, averaging from 0.03 to 0.06 pounds per cow per day. That loss represented less than 5% of the nitrogen fed to cows at the dairy. Methane loss from the lagoons was much greater. In 2009, 0.46 pounds of methane per cow per day was lost. That increased to 0.79 pounds per cow per day in 2010. We observed that the daily pattern of methane emission depended on whether a bubble scum developed on the surface of lagoons. This often resulted in a sudden burst of methane in the morning. Also, methane loss was greatest from the lagoons that directly received wastewater and manure solids from the dairy. Emissions from dairy lagoons are complex and expanding this study would help capture the daily, seasonal and annual changes in emissions.
Technical Abstract: Gaseous emissions of concern from commercial dairy operations include methane and ammonia. Dairy wastewater lagoons are sources of emission for both these gases. We quantified emissions of methane and ammonia from a lagoon system at a commercial open lot dairy in eastern New Mexico using open path laser spectroscopy and an inverse dispersion model during summer in 2009 and 2010. Ammonia flux averaged 49 kg/ha/d in 2009 and 21 kg/ha/d in 2010. On a per head basis, less than 5% of the nitrogen fed to dairy cows was lost from the lagoons as ammonia. In 2010, ammonia emission tended to greater from the effluent inlet lagoons, compared with an overflow lagoon. The lagoons were a significant source of methane, with daily flux averaging 402 kg/head/d in 2009. We were able to segregate emissions between the inlet and overflow lagoons in 2010 and found that methane flux was much greater from inlet lagoons, averaging 1138 kg/ha/d, compared with 151 kg/ha/d from the overflow lagoon. Per capita emission rates were 211 g/head/d in 2009 and 359 g/head/d in 2010. Greater methane emissions in 2010 were partly attributed to volatile solids loading to the inlet lagoons from a large rainstorm three days before the study commenced. Both ammonia and methane emissions are largely temperature-driven processes, so that emissions reported here are probably near the annual maxima for this dairy system. This limited data set illustrates the dynamic nature of emissions and highlights that more extensive data are needed to capture the daily, seasonal, and annual variability of emissions.