Ammonia emissions from manure belt laying hen houses and manure storage

Abstract

Ammonia (NH3) emission rates (ER) of two commercial manure-belt (MB) layer houses in Iowa were monitored for a full year. Hen manure was removed daily from the MB houses. Ammonia and carbon dioxide (CO2) concentrations of incoming and exhaust air streams were measured using custom-designed portable monitoring units (PMUs) that shared similar performance to EPA-approved measurement apparatus. Ventilation rates of the houses were determined by calibrated CO2 mass balance using the latest metabolic rate data for modern laying hens. The data were collected bi-weekly throughout the year, with each collection episode lasting two consecutive days. A total of 108 independent house-day measurements or 5,184 semi-hourly emission data points were involved for the layer houses. Ammonia ER showed considerable diurnal variation, with the peak occurring during manure removal. Data from the 12-month monitoring revealed the NH3 ER (mean standard error) of 0.054 ±0.0035 g NH3 d1 hen'(varying from 0.002 to 0.195 g NH3 d1 hen1) for the belt layer houses with manure removed daily. Seasonal variations in NH3 ER were less noticeable, with the mean ER of 0.042, 0.060, 0.054, and 0.057 g NH3 d1 hen1 for the spring, summer, fall and winter season, respectively. Results of the study contribute to the U.S. national inventory on NH3 emissions from animal feeding operations.