Ammonia Emission Model for Whole Farm Evaluation of Dairy Production Systems

Abstract

1143Ammonia (NH 3 ) emissions vary considerably among farms as influenced by climate and management. Because emission measurement is difficult and expensive, process-based models provide an alternative for estimating whole farm emissions. A model that simulates the processes of NH 3 formation, speciation, aqueous-gas partitioning, and mass transfer was developed and incorporated in a whole farm simulation model (the Integrated Farm System Model). Farm sources included manure on the floor of the housing facility, manure in storage (if used), fieldapplied manure, and deposits on pasture (if grazing is used). In a comprehensive evaluation of the model, simulated daily, seasonal, and annual emissions compared well with data measured over 2 yr for five free stall barns and two manure storages on dairy farms in the eastern United States. In a further comparison with published data, simulated and measured barn emissions were similar over differing barn designs, protein feeding levels, and seasons of the year. Simulated emissions from manure storage were also highly correlated with published emission data across locations, seasons, and different storage covers. For field applied manure, the range in simulated annual emissions normally bounded reported mean values for different manure dry matter contents and application methods. Emissions from pastures measured in northern Europe across seasons and fertilization levels were also represented well by the model. After this evaluation, simulations of a representative dairy farm in Pennsylvania illustrated the effects of animal housing and manure management on whole farm emissions and their interactions with greenhouse gas emissions, nitrate leaching, production costs, and farm profitability.

Process-based Modeling of Ammonia Emission from Beef Cattle Feedyards with the Integrated Farm Systems Model

“…The basic NH 3 emission model used in IFSM to simulate emissions from enclosed structures is documented by Rotz et al (2013). In the current work, several additions were made to better represent open‐lot processes.…”

“…Ammonia flux is then calculated on an hourly time step using an overall mass transfer coefficient multiplied by the difference in NH 3 concentration between the manure and the free air stream, the latter of which is assumed to be negligible (Rotz et al, 2013). To determine the NH 3 concentration at the manure surface, the distribution of TAN between NH 3 and NH 4 + is modeled as a function of manure pH and the K d (Rotz et al, 2013). The TAN concentration in a given hour is determined as the total TAN divided by the total water contained in the upper layer of the manure.…”

Climate change effects on livestock in the Northeast US and strategies for adaptation

“…Reducing losses from one source often leads to greater losses through other pathways. Ammonia volatilization is often the pathway of greatest nitrogen loss, and this emission is highly sensitive to temperature (Rotz et al 2014). Using current manure handling methods, projected climate changes in the NE may increase ammonia losses 20% by midcentury and up to 39% by 2100 (Rotz et al 2016).…”

Research and demonstration to improve air quality for the U.S. animal feeding operations in the 21st century – A critical review

“…Emission modeling of NH 3 (e.g., Pinder et al, 2004;Zhang et al, 2005;Bajwa et al, 2008;Rumburg et al, 2008;Rotz et al, 2014) and odors (e.g., Zhu et al, 2000a;Schiffman et al, , 2008Hoff et al, 2008;Schauberger et al, 2013) from various sources, enteric CH 4 from dairy and cattle (e.g., Kebreab et al, 2008;Sejian et al, 2011), GHG from manure systems (e.g., Li et al, 2012a), and H 2 S from waste treatment systems (e.g., Blunden et al, 2008b) was the primary focus, although there have also been models on indoor air quality related to some of these pollutants (e.g., Sun and Hoff, 2010a,b).…”

“…This modeling approach requires mathematical descriptions of biological, chemical, and physical processes involved in pollutant generation, release, and emissions (Ni et al, 2012b). However, the mechanisms of these processes, especially the generation process, of gases, odorous compounds, and VOCs are still largely unknown, making the models difficult to build without using many assumptions (e.g., Zhang et al, 2005;Rotz et al, 2014).…”