Ammonia Emissions of Laying-Hen Manure as Affected by Accumulation Time

Abstract

A study was conducted to investigate how ammonia (NH₃) emission of laying hen manure is affected by manure accumulation time (MAT). Three trials were conducted. For each trial, 108 W36 laying hens in their prime laying stage were housed in two calorimeter chambers (54 birds per chamber) that were maintained at a temperature of 24±1°C and a concomitant relative humidity of 45 to 65%. Measurements were done continuously over a 5-week period. The environmental variables measured continuously in each chamber included NH₃ gas concentration, ambient temperature, dew-point temperature and air flow rate. On a daily basis, the eggs were collected, counted and weighed. The feed supplied to the birds was also weighed daily. Once a week, 18 hens per chamber were weighed. Ammonia emission rate was then calculated from the differences in NH₃ concentrations between the exhaust and inlet air and the corresponding airflow rate; and it was expressed as mg·d⁻¹·hen^-1, g·d^-1·AU^-1 (AU=animal unit, 500kg live body weight), g·d⁻¹·kg egg^-1, and g·d^-1·kg feed N intake^-1. The results showed that NH₃ emission progressively increased from 101±10 to 605±10mg·d⁻¹·hen^-1 when MAT increased from 1 to 5d. There was a linear relationship between NH₃ emission rate and MAT and the empirical relationship has been developed for the various emission units. The NH₃ emission rates measured in this study contributes to the U.S. national inventory on NH₃ emissions from laying hen operations.