Air Emissions from Animal Feeding Operations

Abstract

The purpose of this paper is to summarize the state of knowledge regarding ammonia (NH 3) emissions from animal feeding operations. Based on the information in published literature, the paper summarizes: • The effects of NH 3 emitted from animal production to the environment. • Emission rates and quantities from animal buildings, storage and treatment facilities, and land application sites. • Ammonia emission measurement methods. • Models for NH 3 emissions, transport, and deposition. • Possible control strategies and technologies. Atmospheric NH 3 is produced by decomposition of organic materials, biomass burning, and fertilizer production and utilization. Ammonia is involved in plant metabolism and can be exchanged between vegetation and the atmosphere. Ammonia emissions abatement has had high environmental priority in parts of Europe in recent years, and ammonia is receiving more attention in the U.S. as a potential air and water quality concern. The primary concerns about ammonia emissions into the atmosphere are: (1) nutrient deposition in nutrient sensitive ecosystems and (2) formation of aerosol particles that may cause haze and impair visibility and are also a concern for potential health effects from respirable particulate matter. Agricultural activities, livestock production in particular, are the largest contributors to NH 3 emissions into the atmosphere. Farm animals consume a considerable amount of protein and other nitrogen (N)-containing substances with their feed. The conversion of dietary N to animal product is relatively inefficient and 50 to 80% of the N consumed is excreted. Ammonia is produced as a consequence of bacterial activity involving the excreted organic N substrates. Ammonia can be emitted from animal housing, manure storage and treatment facilities, and manure land application in animal production operations. Factors that affect NH 3 volatilization include source characteristics (manure, building type, storage and treatment methods, and land application method), pH, temperature, wind speed, and surface characteristics. At this time, the majority of data for emissions from animal feeding operations are from Europe where buildings, manure management , and climate are often different from the U.S. Previously, little research on ammonia emissions occurred in the U.S. before the late 1990s. Progress has been made in the last few years in developing measurement equipment and methods, but the expense of measurement and lack of continuous measurement capability has hindered the development of reliable annual emission factors. Typically, data are collected over short durations, and extrapolations beyond the sampling periods and conditions are prone to error. Recent U.S. studies, however, have introduced long-term continuous monitoring (6 to 15 months) at livestock housing. A national air monitoring study is planning for a 24-month monitoring period at buildings. The ranges of measured emission rates can be large among the European and U.S. data. Reported building emissions range from 0.24 to 6.1, 0.15 to 1.8, 0.34 to 0.9, and 0.61 to 12 g NH 3 /h-AU (1 AU=500 kg mass) for pigs, dairy cattle, beef cattle, and poultry, respectively. Storage/treatment