The Environmental Protection Agency uses air emission data from the National Air Emissions Monitoring Study (NAEMS) to determine regulatory needs, but with data collected from 2007 to 2009, it begs the question of whether it’s applicable to today’s hog farms.
In this project, researchers set out to collect information through a literature review, survey and meta-analysis, to evaluate how well NAEMS monitoring data relate to air emissions from production systems today and in the next few years. Another goal was to provide scientific evidence to estimate the nature and size of emissions changes relative to the NAEMs results. The specific objectives include:
1. Identify and summarize key changes in technology and management practices that could affect air emissions from swine operations in the past decade and identify future trends, through a literature review and survey;
2. Quantify the effects of operating conditions on air emissions through systematic literature review and meta-analysis; and
1. Estimate the nature and size of changes in emissions today relative to the NAEMS data using modeling techniques based on the results from objectives 1 and 2.
Findings: Production efficiencies have reduced manure and air emissions per unit of animal product by 18% from 2010 to 2019 and could drop further with additional feed efficiency gains. The increased use of distiller’s dried grains with solubles (DDGS) on ammonia emissions is uncertain, but the NAEMS hydrogen sulfide emissions rates may be underestimated when DDGS are used. Watering technology developments save water and produce thicker manure, which can reduce ammonia and odor emissions.
Data in recent literature show ammonia emissions for finishers were similar to those in the NAEMS report, but were much lower for today’s gestation facilities. Deep-pit systems had similar results to the NAEMS report for ammonia emissions, however, facilities with pit-recharge systems, especially gestation barns, have much lower rates today.
Emissions from lagoons/basins are highly variable due to environmental conditions and measurement technologies. However, recent literature data indicate the NAEMS emission rates could overestimate ammonia emissions by 3 times and hydrogen sulfide by 7 to 11 times higher. Click here for more details.