Assessment of ammonia emissions from swine facilities in the U.S.-Application of knowledge from experimental research

Ammonia (NH ₃) emitted from animal agriculture is the most important gaseous pollutant in agro-systems. Experimental research, as compared with indirect estimation and hypothetical calculation, on NH ₃ from agriculture is critical for emission assessment, regulation, and abatement. Research involving field-scale monitoring of NH ₃ emissions from U.S. swine facilities has greatly expanded in the past 15 years. However, published NH ₃ calculation tools, including emission factors, and U.S. EPA (United States Environmental Protection Agency) inventories in this field were largely based on non-U.S. research. While seasonal and diurnal variations of NH ₃ concentrations and emissions are acknowledged, most field studies, which these tools depended on, produced data that only represented a fraction of the overall picture of NH ₃ emissions because of technological and financial limitations. Different methodologies and technologies have been used in NH ₃ emission investigations but not compared systematically. Methodology, equipment, and software used in sampling and measurement, and methodology and software used in data processing and emission rate calculation can introduce variations into the results. Because of the lack of standardized methods and procedures, it is difficult to identify and quantify measurement and calculation errors. Although a few comprehensive field studies have been conducted that were long enough to cover seasonal and even annual variations, and continuous enough to cover diurnal and dynamic emission variations, there is a considerable delay of in-depth interpretation and publication of data following comprehensive monitoring projects in the U.S. There is also a lag of adopting/updating the latest NH ₃ emission factors from comprehensive field studies in country-wide NH ₃ emission inventories. In addition, there have been discrepancies between data obtained from research and data published by governmental and other agencies. Future development in this field will require that methodologies and criteria be made to weigh data from different projects to develop emission factors, more emphasis be put on application of comprehensive research results, more intensive and extensive field monitoring be conducted, standards and protocols for monitoring and data calculation be developed, and more investment be made on post-measurement data processing/analyzing/interpretation and development of advanced computer software.