2008 Annual Report 1a.Objectives (from AD-416) To develop mathematical relationships that describe the major processes involved in the formation, release, and convective transfer of gaseous compounds from silage, and to calibrate those relationships to accurately predict emissions from feeds in silos and feed bunks. 1b.Approach (from AD-416) Mathematical relationships will be derived that describe the biological, chemical, and physical processes involved in the formation, release, and transfer of the major gaseous compounds found in silage feeds on dairy farms. These relationships will be derived based upon theoretical or scientific understanding of the processes where rates are controlled by the characteristics of the feed and the surrounding environment. Parameters for these relationships will be determined using experimental emissions data collected in collaboration with researchers at the Pennsylvania State University, the University of California at Davis, and other laboratories in the USA and Europe. Experiments will be conducted to measure the dissociation and mass transfer coefficients for major silage compounds. After the relationships are developed and working parameters are established, these models will be evaluated using independent data sets collected through the measurement of emissions from silos and feed bunks on dairy farms. Gaseous emissions of interest include ammonia, carbon dioxide, nitrous oxide, methane, and volatile organic compounds with particular emphasis on the anticipated most important compounds of ethanol and methanol. As models for individual compounds are developed and validated, they will be integrated in a simulation model that predicts emission levels throughout the year as a function of the feed and animal management used on the farm. 3.Progress Report This work contributes to Objective 1 of the in-house project: Develop process-based relationships that predict emissions of ammonia, hydrogen sulfide, volatile organic compounds, and greenhouse gases from animal, feed, and manure sources on dairy farms. This project is a component of a national effort funded by dairy producers to develop a process-based model for estimating gaseous emissions from dairy farms and evaluating the benefits of reduction strategies. The project was just initiated. The funds received are being used to support a Research Associate. A position has been advertised and interviews are being conducted to recruit a suitable candidate. This project addresses the NP 203 Air Quality program, component III: Malordorous Compounds and the NP 207 program vision of “Integrated agricultural systems that are competitive, profitable, sustainable, and environmentally compatible”.